liu.seSearch for publications in DiVA
Change search
Refine search result
1 - 30 of 30
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ciechonski, Rafal
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pedersen, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lundskog, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Forsberg, Urban
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    In-situ treatment of GaN epilayers in hot-wall MOCVDManuscript (Other academic)
  • 2.
    Ciechonski, Rafal
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    High 2DEG mobility of HEMT structures grown on 100 mm SI 4H-SiC substrates by hot-wall MOCVD2007In: Journal of Applied PhysicsArticle in journal (Refereed)
  • 3.
    Eriksson, Martin. O.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    The Dynamics of Charged and Neutral Excitons in an InGaN Quantum Dot on a GaN PyramidManuscript (preprint) (Other academic)
    Abstract [en]

    The neutral (X0) and negatively charged excitons (X-) in an InGaN QD on a GaN pyramid is studied by the timeintegrated micro-photoluminescence (μPL) and time-resolved micro-photoluminescence (TRμPL) microcopies. Both X0 and X- exhibit mono-exponential decay curves with fitted lifetimes of 310 and 140 ps, respectively. Neither energy shifts nor changes in the life times X0 and X- with increasing excitation power were observed, indicating the QD is small and free from the quantum confine Stark effect. The TRμPL is not only a powerful technique for studying the dynamics of exciton in QDXs, but also for the identification of exciton complexes in QDs.

  • 4.
    Fagerlind, M.
    et al.
    Chalmers.
    Allerstam, F.
    Chalmers.
    Sveinbjornsson, E.O.
    Chalmers.
    Rorsman, N.
    Chalmers.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Investigation of the interface between silicon nitride passivations and AlGaN/AlN/GaN heterostructures by C(V) characterization of metal-insulator-semiconductor-heterostructure capacitors2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 1, p. 014508-Article in journal (Refereed)
    Abstract [en]

    Capacitance-voltage [C(V)] measurements of metal-insulator-semiconductor-heterostructure capacitors are used to investigate the interface between silicon nitride passivation and AlGaN/AlN/GaN heterostructure material. AlGaN/AlN/GaN samples having different silicon nitride passivating layers, deposited using three different deposition techniques, are evaluated. Different interface state distributions result in large differences in the C(V) characteristics. A method to extract fixed charge as well as traps from the C(V) characteristics is presented. Rough estimates of the emission time constants of the traps can be extracted by careful analysis of the C(V) characteristics. The fixed charge is positive for all samples, with a density varying between 1.3 x 10(12) and 7.1 x 10(12) cm(-2). For the traps, the peak density of interface states is varying between 16 x 10(12) and 31 x 10(12) cm(-2) eV(-1) for the three samples. It is concluded that, of the deposition methods investigated in this report, the low pressure chemical vapor deposited silicon nitride passivation shows the most promising results with regards to low densities of interface states.

  • 5.
    Forsberg, Urban
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ciechonski, Rafal
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Improved hot-wall MOCVD growth of highly uniform AlGaN/GaN/HEMT structures2009In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 10, p. 3007-3010Article in journal (Refereed)
    Abstract [en]

    The inherent advantages of the hot-wall metal organic chemical vapor deposition (MOCVD) reactor (low temperature gradients, less bowing of the wafer during growth, efficient precursor cracking) compared to a cold-wall reactor make it easier to obtain uniform growth. However, arcing may occur in the growth chamber during growth, which deteriorates the properties of the grown material. By inserting insulating pyrolytic BN (PBN) stripes in the growth chamber we have completely eliminated this problem. Using this novel approach we have grown highly uniform, advanced high electron mobility transistor (HEMT) structures on 4 semi-insulating (SI) SiC substrates with gas-foil rotation of the substrate. The nonuniformities of sheet resistance and epilayer thickness are typically less than 3% over the wafer. The room temperature hall mobility of the 2DEG is well above 2000 cm(2)/V s and the sheet resistance about 270 Omega/sqr.

  • 6.
    Henry, Anne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Large area mapping of the alloy composition of AlxGa1-xN using infrared reflectivity2009In: PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, ISSN 1862-6254, Vol. 3, no 5, p. 145-147Article in journal (Refereed)
    Abstract [en]

    The energy position of a dip observed in the IR-reflectance spectra recorded from wurtzite c-plane AlxGa1-xN epitaxial films grown on SiC substrate reflects the composition of the alloy. A calibration procedure is presented with the possibility of mapping for large area wafer. The technique is non-destructive, scalable and fast. The limitations are discussed and comparisons with other techniques are made.

  • 7.
    Henry, Anne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ivanov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    AlGaN Multiple Quantum Wells and AlN Grown in a Hot-wall MOCVD for Deep UV Applications2009In: ECS Transactions, Vol. 25, Iss. 8, ECS , 2009, p. 837-844Conference paper (Refereed)
    Abstract [en]

    AlxGa1-xN multiple quantum wells (MQW) were grown on AlN epilayer grown on 4H-SiC substrate. The growth was performed without interruption in a horizontal hot-wall MOCVD reactor using a mixture of hydrogen and nitrogen as carrier gases. The precursors were ammonia, trimethylaluminum and trimethylgallium. Results obtained from X-ray diffraction and infra-red reflectance were used to obtain the composition of the films when growing simple AlxGa1 xN layer. Visible reflectance was used to evaluate the thickness of the films. Finally the MQW parameters as thicknesses and composition variation were obtained by scanning transmission electron microscopy and demonstrated an agreement with the growth parameters used

  • 8.
    Holtz, Per Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chi-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Deterministic Single InGaN Quantum Dots grown on GaN Micro-Pyramid Arrays2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 646, p. 34-37Article in journal (Other academic)
    Abstract [en]

    InGaN quantum dots (QDs) formed on top of GaN pyramids have been fabricated by means of selective area growth employing hot wall MOCVD. Upon regrowth of a patterned substrate, the growth will solely occur in the holes, which evolve into epitaxially grown wurtzite based pyramids. These pyramids are subsequently overgrown by a thin optically active InGaN well. The QDs are preferably nucleating at the apices of the pyramids as evidenced by the transmission electron microscopy (TEM). The emission from these QDs have been monitored by means of microphotoluminescence (µPL), in which single emission lines have been detected with a sub-meV line width. The µPL measurements undoubtedly reveal that the QDs are located in the apexes of the pyramids, since the sharp emission peaks can only be monitored as the excitation laser is focused on the apices in the µPL. It is also demonstrated that the emission energy can be changed in a controlled way by altering the growth conditions, like the growth temperature and/or composition, for the InGaN layers. The tip of the GaN pyramid is on the nm scale and can be made sharp or slightly truncated. TEM analysis combined with µPL results strongly indicate that the Stranski-Krastanow growth modepreferably is taking place at the microscopic c-plane truncation of the GaN pyramid. Single emission lines with a high degree of polarization is a common feature observed for individual QDs. This emission remains unchanged with increasing the excitation power and sample temperature. An in-plane elongated QD forming a shallow potential with an equal number of electrons and holes is proposed to explain the observed characteristics of merely a single exciton emission with a high degree of polarization.

  • 9.
    Holtz, Per-Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Larsson, L A
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Dufåker, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Moskalenko, Evgenii
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dimastrodonato, V
    National University of Ireland University of Coll Cork.
    Mereni, L
    National University of Ireland University of Coll Cork.
    Pelucchi, E
    National University of Ireland University of Coll Cork.
    Optical characterization of individual quantum dots2012In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 407, no 10, p. 1472-1475Article in journal (Refereed)
    Abstract [en]

    Optical characterization of single quantum dots (QDs) by means of micro-photoluminescence (mu PL) will be reviewed. Both QDs formed in the Stranski-Krastanov mode as well as dots in the apex of pyramidal structures will be presented. For InGaAs/GaAs dots, several excitonic features with different charge states will be demonstrated. By varying the magnitude of an external electric or magnetic field and/or the temperature, it has been demonstrated that the transportation of carriers is affected and accordingly the charge state of a single QD can be tuned. In addition, we have shown that the charge state of the QD can be controlled also by pure optical means, i.e. by altering the photo excitation conditions. Based on the experience of the developed InAs/GaAs QD system, similar methods have been applied on the InGaN/GaN QD system. less thanbrgreater than less thanbrgreater thanThe coupling of LO phonons to the QD emission is experimentally examined for both charged and neutral excitons in single InGaAs/GaAs QDs in the apex of pyramidal structures. It is shown that the positively charged exciton exhibits a significantly weaker LO phonon coupling in the mu PL spectra than the neutral and negatively charged species, a fact, which is in consistency with model simulations performed.

  • 10.
    Hsu, Chih-Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Optical characterization of InGaN quantum dots on GaN pyramids grown by MOCVD2010Conference paper (Refereed)
  • 11.
    Hsu, Chih-Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Single Excitons in InGaN Quantum Dots on GaN Pyramid Arrays2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 6, p. 2415-2418Article in journal (Refereed)
    Abstract [en]

    Fabrication of single InGaN quantum dots (QDs) on top of GaN micropyramids is reported. The formation of single QDs is evidenced by showing single sub-millielectronvolt emission lines in microphotoluminescence (mu PL) spectra. Tunable QD emission energy by varying the growth temperature of the InGaN layers is also demonstrated. From mu PL, it is evident that the QDs are located in the apexes of the pyramids. The fact that the emission lines of the QDs are linear polarized in a preferred direction implies that the apexes induce unidirected anisotropic fields to the QDs. The single emission lines remain unchanged with increasing the excitation power and/or crystal temperature. An in-plane elongated QD forming a shallow potential with an equal number of trapped electrons and holes is proposed to explain the absence of other exciton complexes.

  • 12.
    Hsu, Chih-Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Controlled Growth of GaN Pyramidal template hosting InGaN Quantum DotsManuscript (preprint) (Other academic)
    Abstract [en]

    The emission properties of InGaN grown on hexagonal GaN pyramids with various pitch distances (PD) are studied. Emissions associated with InGaN quantum wells (QWs) and InGaN quantum dots (QDs) can be identified. The emission energies of InGaN QWs and QDs shift toward opposite directions with increasing PD; red-shift for QWs and blue-shift for QDs. Based on the source supply mechanism in a selective area growth process, the formation of InGaN QDs on GaN pyramids is believed to be a combined effect of Stranski-Krastanow growth mode and spinodal decomposition taking place at the microscopic (0001) surfaces on GaN pyramids.

  • 13.
    Hsu, Chih-Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Moskalenko, Evgenii
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Eriksson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik K.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    The charged exciton in an InGaN quantum dot on a GaN pyramid2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 1Article in journal (Refereed)
    Abstract [en]

    The emission of a charged exciton in an InGaN quantum dot (QD) on top of a GaN pyramid is identified experimentally. The intensity of the charged exciton exhibits the expected competition with that of the single exciton, as observed in temperature-dependent micro-photoluminescence measurements, performed with different excitation energies. The non-zero charge state of this complex is further supported by time resolved micro-photoluminescence measurements, which excludes neutral alternatives of biexciton. The potential fluctuations in the vicinity of the QD that localizes the charge carriers are proposed to be responsible for the unequal supply of electrons and holes into the QD.

  • 14.
    Hsu, Hsu-Cheng
    et al.
    National Cheng Kung University, Taiwan National Cheng Kung University, Taiwan .
    Hsu, Geng-Ming
    National Taiwan University, Taiwan .
    Lai, Yu-shiung
    National Taiwan University, Taiwan .
    Chuan Feng, Zhe
    National Taiwan University, Taiwan .
    Tseng, Shuo-Yen
    National Cheng Kung University, Taiwan National Cheng Kung University, Taiwan .
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, Kuei-Hsien
    National Taiwan University, Taiwan Academic Sinica, Taiwan .
    Chen, Li-Chyong
    National Taiwan University, Taiwan .
    Polarized and diameter-dependent Raman scattering from individual aluminum nitride nanowires: The antenna and cavity effects2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 12, p. 121902-Article in journal (Refereed)
    Abstract [en]

    Raman scattering of individual aluminum nitride (AlN) nanowires is investigated systematically. The axial direction of single nanowire can be rapidly verified by polarized Raman scattering. The angular dependencies of E-2(high) mode show strongly anisotropic behavior in smaller nanowires, which results from optical antenna effect. Raman enhancement (RE) per unit volume of E-2(high) increases with decreasing diameter of nanowires. Compared to the thin film, similar to 200-fold increase of RE is observed in AlN nanowires having diameter less than 50 nm, which is far beyond the quantum confinement regime. Such a large RE can be attributed to the effects of resonant cavity and stimulated Raman scattering.

  • 15.
    J T Simms, R J T
    et al.
    University of Bristol.
    Uren, M J
    QinetiQ Ltd.
    Martin, T
    QinetiQ Ltd.
    Powell, J
    QinetiQ Ltd.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kuball, M
    University of Bristol.
    Micro-Raman spectroscopy as a voltage probe in AlGaN/GaN heterostructure devices: Determination of buffer resistances2011In: SOLID-STATE ELECTRONICS, ISSN 0038-1101, Vol. 55, no 1, p. 5-7Article in journal (Refereed)
    Abstract [en]

    A time-resolved micro-Raman technique was developed to probe the transient voltage in the GaN buffer layer of AlGaN/GaN heterostructure devices. The transient potential distribution under Ohmic contacts of devices behaved like a capacitance-resistance coupled network, with a decrease in amplitude and phase shift of the potential as a function of operating voltage frequency. This phenomenon was used to extract a value of 0.6 M Omega/square for sheet resistance of the AIN nucleation layer at the GaN/SiC interface from the characteristic RC value of the network. This demonstrates the effectiveness of this voltage probe technique as a non-invasive method of characterizing nucleation layers.

  • 16.
    Kakanakova-Georgieva, Anelia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ciechonski, Rafal
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hot-Wall MOCVD for Highly Efficient and Uniform Growth of AIN2009In: Crystal Growth & Design, ISSN 1528-7483, Vol. 9, no 2, p. 880-884Article in journal (Refereed)
    Abstract [en]

    We demonstrated successful growth of AIN at a temperature of 1200 degrees C in a set of hot-wall MOCVD systems with the possibility of straightforward scaling up the process on larger wafer areas to meet the demand of device technologies. We outlined several aspects of the carefully optimized design and process parameters with relevance to achievement of a high overall growth rate (1 and up to 2 mu m/h), efficiency, and uniformity, which to a great extent depends on how consumption of growth-limiting species by gas-phase adduct formation can actively be prevented. Mixing of the precursors upstream from the deposition area facilitates uniform epitaxial growth, while the greater uniformity of substrate temperature inherent to the hot-wall reactor and rotation of the wafer are of fundamental importance for layer-growth uniformity. The AIN layer thickness can be controlled with an accuracy of +/- 1.3% on 2 in. wafers. The low-temperature cathodoluminescence spectrum of the AIN epitaxial material is strongly dominated by the intense near band-gap deep UV emission at about 208 nm.

  • 17.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Controlled growth of hexagonal GaN pyramids and InGaN QDs2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Gallium-nitride (GaN) and its related alloys are direct band gap semiconductors, with a wide variety of applications. The white light emitting diode (LED) is of particular importance as it is expected to replace energy inefficient light bulb and hazardous incandescent lamps used today. However, today’s planar hetero epitaxial grown LEDs  structures contain an unavoidable number of dislocations, which serves as non-radiative recombination centers. The dislocations harm the luminous efficiency of the LEDs and generate additional heat. Pseudomorphically grown quantum dots (QDs) are expected to be dislocation free thus the injected carriers captured by the QDs essentially recombine radiatively since the dislocations remain outside the QD. Furthermore the continuous character of the density of states in bulk materials is redistributed when the size of the dot is reduced within the Bohr radius of the material. Fully discret energy levels are eventually reached, which offers additional control of the optical properties. The Coulomb interaction between the confined carriers also has influence on the emission energy of the recombining carriers, which opens up the possibility of manufacturing novel light sources such as the single photon emitter. Single photon emitters are essential building blocks for quantum cryptography and teleportation applications.

    The main contribution of the present work is the investigation of growth and characterization of sitecontrolled indium-gallium-nitride QDs embedded in GaN matrixes. The goal has been to demonstrate the ability to grow site-controlled InGaN QDs at the apex of hexagonal GaN pyramids in a controlled way using hot-wall metal organic chemical vapor deposition (MOCVD). Strong emphasis was set on the controlled growth of InGaN QDs. For example the growth of a single InGaN QD located at the apex of hexagonal GaN pyramids with tunable emission energy, the QD emission energy impact on the mask design, and a novel approach for the growth of InGaN QDs with polarization deterministic photon vectors were reported. The thesis is mainly based on experimental investigations by secondary electron microscope (SEM), micro photo-luminescence (μPL), and scanning transition electron microscopy ((S)TEM) characterization techniques.

    In Paper 1 and 2, we present the growth of symmetric GaN hexagonal pyramids which served as template for the InGaN QDs grown. In paper 1, it was concluded that the selective area growth (SAG) of hexagonal GaN pyramids by MOCVD through symmetric openings in a SIN mask roughly can be divided in two regimes where either the pyramid expands laterally or not. When the pyramid expanded laterally the resulting pyramid apex became (0001) truncated even after prolonged growth times. Lateral expansion also had major impact on the pyramid-to-pyramid uniformity. In paper 2, the MOCVD process parameter impact on the pyramid morphology was investigated. By tuning the growth temperature, the ammonia, and TMGa-flows a self limited pyramid structure with only {1101} facets visible was achieved. The presence of the {1101}, {1102}, and {1100} facets were discussed from surface stabilities under various growth conditions.

    Paper 3 and 4 concern the growth of InGaN QDs located at the apex of hexagonal GaN pyramids. In paper 3, we showed that it is possible to grow single QDs at the apex of hexagonal pyramids with emission line widths in the Ångström range. The QD emission energy was demonstrated to be tunable by the growth temperature. Basic spectroscopy data is also presented on a single QD in paper 3. In paper 4, the growth mechanisms of the QDs presented in paper 3 are presented. We concluded that (0001) truncated GaN pyramid base initiated the growth of InGaN QDs which gave rise to narrow luminescence peaks in the μPL spectra.

    In paper 5, the QD emission energy impact of the mask design was investigated. To our big surprise the QD emission energy increased with increasing pyramid pitch while the emission energy of the InGaN quantum wells located on the {1101} facets of the pyramids energetically shifted towards lower energies. The energy shift at the apex was found to be associated with the (0001) truncation diameter of the underlying GaN pyramid since no energy shift was observed for (0001) truncated pyramids with truncation diameters larger than 100 nm.

    In paper 6, the symmetry of the GaN pyramids were intentionally broken through the introduction of elongated openings in the SiN mask (symmetric openings was used in the previous five papers). The emission polarization vectors of the subsequently grown InGaN QDs were deterministically linked to the in-plane orientation of the pyramid it was nucleated upon, implying that the QDs inhibit an inplane anisotropy directly inherited from the pyramid template.

    Finally, paper 7 describes a hot-wall MOCVD reactor improvement by inserting insulating pyrolytic boron-nitride (PBN) stripes in the growth chamber. By doing this, we have completely eliminated the arcing problem between different susceptor parts. As a consequence, the reactor gained run-to-run reproducibility. Growth of state of the art advanced aluminum-gallium-nitride high electron mobility transistor structures on a 100 mm wafer with electron mobility above 2000 Vs/cm2 was demonstrated by the improved process.

    List of papers
    1. Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD
    Open this publication in new window or tab >>Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD
    Show others...
    2013 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 363, p. 287-293Article in journal (Refereed) Published
    Abstract [en]

    Hexagonal GaN pyramids have been fabricated by hot-wall metal organic chemical vapor deposition (hot-wall MOCVD) and the growth evolution have been studied. It was concluded that the pyramid growth can be divided into two regimes separated by the adsorption kinetics of the {1101} surfaces of the pyramids. In the adsorption regime, the pyramids grow simultaneously in the <1101> and [0001] -directions. In the zero-adsorption regime the pyramids grow only in the [0001] direction. Thus the pyramid growth ceases when the (0001) facet growth has been terminated. Large arrays consisting of highly uniform pyramids with apex radii of 3 nm or less were achieved in the zeroadsorption regime. The growth-regime type was concluded to have a large impact on the uniformity degradation of the pyramids, and their optical properties. The impacts of threading dislocations which enter the pyramid from underneath are also discussed.

    Keywords
    A3. Hot wall epitaxy A3. Metalorganic vapor phase epitaxy A3. Selective epitaxy B1. Nitrides
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-79317 (URN)10.1016/j.jcrysgro.2012.11.014 (DOI)000313205400047 ()
    Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2017-12-07Bibliographically approved
    2. Morphology control of hot-wall MOCVD selective area -grown hexagonal GaN pyramids
    Open this publication in new window or tab >>Morphology control of hot-wall MOCVD selective area -grown hexagonal GaN pyramids
    2012 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 12, no 11, p. 5491-5496Article in journal (Refereed) Published
    Abstract [en]

    Morphological variations of gallium polar (0001) oriented hexagonal GaN pyramids grown by hotwall metal organic chemical vapor deposition under various growth conditions are investigated. The stability of the semi-polar {1102} and non-polar {1100} facets are particularly discussed. The presence of the {1102} facets near the apex of the pyramid was found to be controllable by tuning the absolute flow rate of ammonia during the growth. Vertical non-polar {1100} facets appeared ingallium rich-conditions which automatically were created when the growth time was prolonged beyond pyramid completion. The result was attributed to a gallium passivation of the {1100} surface.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-79320 (URN)10.1021/cg301064p (DOI)000311240100041 ()
    Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2017-12-07Bibliographically approved
    3. Single Excitons in InGaN Quantum Dots on GaN Pyramid Arrays
    Open this publication in new window or tab >>Single Excitons in InGaN Quantum Dots on GaN Pyramid Arrays
    Show others...
    2011 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 6, p. 2415-2418Article in journal (Refereed) Published
    Abstract [en]

    Fabrication of single InGaN quantum dots (QDs) on top of GaN micropyramids is reported. The formation of single QDs is evidenced by showing single sub-millielectronvolt emission lines in microphotoluminescence (mu PL) spectra. Tunable QD emission energy by varying the growth temperature of the InGaN layers is also demonstrated. From mu PL, it is evident that the QDs are located in the apexes of the pyramids. The fact that the emission lines of the QDs are linear polarized in a preferred direction implies that the apexes induce unidirected anisotropic fields to the QDs. The single emission lines remain unchanged with increasing the excitation power and/or crystal temperature. An in-plane elongated QD forming a shallow potential with an equal number of trapped electrons and holes is proposed to explain the absence of other exciton complexes.

    Place, publisher, year, edition, pages
    American Chemical Society, 2011
    Keywords
    InGaN, quantum dots, pyramid, exciton, photoluminescence
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-69169 (URN)10.1021/nl200810v (DOI)000291322600038 ()
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-12-11Bibliographically approved
    4. InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids
    Open this publication in new window or tab >>InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids
    Show others...
    2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 30, p. 305708-Article in journal (Refereed) Published
    Abstract [en]

    Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal–organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.

    Place, publisher, year, edition, pages
    Institute of Physics (IOP), 2012
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-79321 (URN)10.1088/0957-4484/23/30/305708 (DOI)000306333500030 ()
    Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2017-12-07Bibliographically approved
    5. Unexpected behavior of InGaN quantum dot emission energy located at apices of hexagonal GaN pyramids
    Open this publication in new window or tab >>Unexpected behavior of InGaN quantum dot emission energy located at apices of hexagonal GaN pyramids
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    InGaN quantum dots (QDs) have been grown at the apices of hexagonal GaN pyramids. The pyramids were selectively grown on a (0001) oriented GaN template through circular apertures in a SiN mask positioned in square arrays. The emission of the InGaN QDs was shifted towards higher energies when the center-to-center distance of the pyramids was increased, while the emission from InGaN quantum wells located on the {1101} facets of the pyramids was energetically shifted towards lower energies. No energy shift was observed for (0001) truncated pyramids with truncation diameters larger than 100 nm.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-79322 (URN)
    Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2016-08-31Bibliographically approved
    6. Polarization-controlled photon emission from site-controlled InGaN quantum dots
    Open this publication in new window or tab >>Polarization-controlled photon emission from site-controlled InGaN quantum dots
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The optical polarization properties of hot-wall MOCVD grown of InGaN quantum dots (QDs) located at the apex of elongated hexagonal GaN pyramids are presented. The QDs showed spectrally narrow and strongly linearly polarized emission lines with average polarization ratios above 0.8 in the microphoto-luminescence spectra. By a comprehensive statistical analysis including more than 1000 InGaN QDs it was concluded that the polarization direction of the QDs follows the spatial elongation of the underlying GaN pyramids when elongated in the <2110> directions.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-79323 (URN)
    Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2015-01-23Bibliographically approved
    7. Improved hot-wall MOCVD growth of highly uniform AlGaN/GaN/HEMT structures
    Open this publication in new window or tab >>Improved hot-wall MOCVD growth of highly uniform AlGaN/GaN/HEMT structures
    Show others...
    2009 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 10, p. 3007-3010Article in journal (Refereed) Published
    Abstract [en]

    The inherent advantages of the hot-wall metal organic chemical vapor deposition (MOCVD) reactor (low temperature gradients, less bowing of the wafer during growth, efficient precursor cracking) compared to a cold-wall reactor make it easier to obtain uniform growth. However, arcing may occur in the growth chamber during growth, which deteriorates the properties of the grown material. By inserting insulating pyrolytic BN (PBN) stripes in the growth chamber we have completely eliminated this problem. Using this novel approach we have grown highly uniform, advanced high electron mobility transistor (HEMT) structures on 4 semi-insulating (SI) SiC substrates with gas-foil rotation of the substrate. The nonuniformities of sheet resistance and epilayer thickness are typically less than 3% over the wafer. The room temperature hall mobility of the 2DEG is well above 2000 cm(2)/V s and the sheet resistance about 270 Omega/sqr.

    Keywords
    Metalorganic chemical vapor deposition, Nitrides, High electron mobility transistors
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19663 (URN)10.1016/j.jcrysgro.2009.01.045 (DOI)
    Note
    Original Publication: Urban Forsberg, Anders Lundskog, A Kakanakova-Georgieva, Rafal Ciechonski and Erik Janzén, Improved hot-wall MOCVD growth of highly uniform AlGaN/GaN/HEMT structures, 2009, JOURNAL OF CRYSTAL GROWTH, (311), 10, 3007-3010. http://dx.doi.org/10.1016/j.jcrysgro.2009.01.045 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/Available from: 2009-08-17 Created: 2009-07-10 Last updated: 2017-12-13Bibliographically approved
  • 18.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Morphology control of hot-wall MOCVD selective area -grown hexagonal GaN pyramids2012In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 12, no 11, p. 5491-5496Article in journal (Refereed)
    Abstract [en]

    Morphological variations of gallium polar (0001) oriented hexagonal GaN pyramids grown by hotwall metal organic chemical vapor deposition under various growth conditions are investigated. The stability of the semi-polar {1102} and non-polar {1100} facets are particularly discussed. The presence of the {1102} facets near the apex of the pyramid was found to be controllable by tuning the absolute flow rate of ammonia during the growth. Vertical non-polar {1100} facets appeared ingallium rich-conditions which automatically were created when the growth time was prolonged beyond pyramid completion. The result was attributed to a gallium passivation of the {1100} surface.

  • 19.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ciechonski, Rafal
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Fagerlind, M.
    Shiu, J-Y.
    Rorsman, N.
    Highly Uniform Hot-Wall MOCVD Growth of High-Quality AlGaN/GaN HEMT-Structures on 100 mm Semi-Insulating 4H-SiC Substrates2007In: ICNS-7,2007, 2007Conference paper (Other academic)
    Abstract [en]

       

  • 20.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Amloy, Supaluck
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Department of Physics, Faculty of Science, Thaksin University, Thailand.
    Nilsson, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots2014In: Light: Science & Applications, ISSN 2095-5545, Vol. 3, article id e139Article in journal (Refereed)
    Abstract [en]

    Semiconductor quantum dots (QDs) have been demonstrated viable for the emission of single photons on demand during the past decade. However, the synthesis of QDs emitting photons with pre-defined and deterministic polarization vectors has proven arduous. The access of linearly-polarized photons is essential for various applications. In this report, a novel concept to directly generate linearly-polarized photons is presented. This concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids, by which predefined orientations herald the polarization vectors of the emitted photons from the QDs. This growth scheme should allow fabrication of ultracompact arrays of photon emitters, with a controlled polarization direction for each individual QD emitter.

  • 21.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Nilsson, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Polarization-controlled photon emission from site-controlled InGaN quantum dotsManuscript (preprint) (Other academic)
    Abstract [en]

    The optical polarization properties of hot-wall MOCVD grown of InGaN quantum dots (QDs) located at the apex of elongated hexagonal GaN pyramids are presented. The QDs showed spectrally narrow and strongly linearly polarized emission lines with average polarization ratios above 0.8 in the microphoto-luminescence spectra. By a comprehensive statistical analysis including more than 1000 InGaN QDs it was concluded that the polarization direction of the QDs follows the spatial elongation of the underlying GaN pyramids when elongated in the <2110> directions.

  • 22.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Nilsson, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD2013In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 363, p. 287-293Article in journal (Refereed)
    Abstract [en]

    Hexagonal GaN pyramids have been fabricated by hot-wall metal organic chemical vapor deposition (hot-wall MOCVD) and the growth evolution have been studied. It was concluded that the pyramid growth can be divided into two regimes separated by the adsorption kinetics of the {1101} surfaces of the pyramids. In the adsorption regime, the pyramids grow simultaneously in the <1101> and [0001] -directions. In the zero-adsorption regime the pyramids grow only in the [0001] direction. Thus the pyramid growth ceases when the (0001) facet growth has been terminated. Large arrays consisting of highly uniform pyramids with apex radii of 3 nm or less were achieved in the zeroadsorption regime. The growth-regime type was concluded to have a large impact on the uniformity degradation of the pyramids, and their optical properties. The impacts of threading dislocations which enter the pyramid from underneath are also discussed.

  • 23.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Unexpected behavior of InGaN quantum dot emission energy located at apices of hexagonal GaN pyramidsManuscript (preprint) (Other academic)
    Abstract [en]

    InGaN quantum dots (QDs) have been grown at the apices of hexagonal GaN pyramids. The pyramids were selectively grown on a (0001) oriented GaN template through circular apertures in a SiN mask positioned in square arrays. The emission of the InGaN QDs was shifted towards higher energies when the center-to-center distance of the pyramids was increased, while the emission from InGaN quantum wells located on the {1101} facets of the pyramids was energetically shifted towards lower energies. No energy shift was observed for (0001) truncated pyramids with truncation diameters larger than 100 nm.

  • 24.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 30, p. 305708-Article in journal (Refereed)
    Abstract [en]

    Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal–organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.

  • 25.
    Palisaitis, Justinas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Characterization of InGaN/GaN quantum well growth using monochromated valence electron energy loss spectroscopy2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 3, p. 034302-Article in journal (Refereed)
    Abstract [en]

    The early stages of InGaN/GaN quantum wells growth for In reduced conditions have been investigated for varying thickness and composition of the wells. The structures were studied by monochromated STEM–VEELS spectrum imaging at high spatial resolution. It is found that beyond a critical well thickness and composition, quantum dots (>20 nm) are formed inside the well. These are buried by compositionally graded InGaN, which is formed as GaN is grown while residual In is incorporated into the growing structure. It is proposed that these dots may act as carrier localization centers inside the quantum wells.

  • 26.
    Pedersen, Henrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Leone, Stefano
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Beyer, Franziska
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lundskog, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chloride-based SiC epitaxial growth2009In: Materials Science Forum Vols. 615-617, Trans Tech Publications , 2009, p. 89-Conference paper (Refereed)
    Abstract [en]

    Some aspects of the chloride-based CVD growth process have been investigated by using both the approach to add HCl to the standard precursors or/and by using the single molecule precursor methyltrichlorosilane (MTS). The efficiency of the process for different precursors, the growth rate stability and the effect that the Cl/Si-ratio has on the growth have been studied. MTS is showed to be the most efficient precursor; the growth can be hindered by to much chlorine in the gas mixture. The Cl/Si-ratio is also found to be a process parameter that affects the amount of incorporated nitrogen in the epilayers.

  • 27.
    Pedersen, Henrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Growth characteristics of chloride-based SiC epitaxial growth2008In: Physica status solidi (RRL) - Rapid Research Letters, ISSN 1862-6270, Vol. 2, no 6, p. 278-280Article in journal (Refereed)
    Abstract [en]

    In this study some aspects of the chloride-based CVD growth process have been investigated by using both the approach to add HCl to the standard precursors and by using the single molecule precursor methyltrichlorosilane (MTS). The efficiency of the process for different precursors, the growth rate stability and the effect that the C/Si and Cl/Si ratios have on the growth are studied. It is found that MTS is the most efficient precursor and that the growth becomes carbon limited at C/Si < 1.

  • 28.
    Pozina, Galia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hemmingsson, Carl
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Forsberg, Urban
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lundskog, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Time-resolved photoluminescence properties of AlGaN/AlN/GaN high electron mobility transistor structures grown on 4- SiC substrate2008In: 8th International Conference on Physics of Light-Matter Coupling in Nanostructures,2008, 2008Conference paper (Other academic)
  • 29.
    Pozina, Galia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Time-resolved photoluminescence properties of AlGaN/AlN/GaN high electron mobility transistor structures grown on 4H-SiC substrate2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, no 11, p. 113513-Article in journal (Refereed)
    Abstract [en]

    AlGaN/AlN/GaN high electron mobility transistor heterostructures grown by metal-organic chemical vapor deposition have been studied by temperature dependent time-resolved photoluminescence. The AlGaN-related emission is found to be sensitive to the excitation power and to the built-in internal electric field. In addition, this emission shows a shift to higher energy with the reduction in the excitation density, which is rather unusual. Using a self-consistent calculation of the band potential profile, we suggest a recombination mechanism for the AlGaN-related emission involving electrons confined in the triangular AlGaN quantum well and holes weakly localized due to potential fluctuations.

  • 30.
    Riedel, Gernot J
    et al.
    University of Bristol.
    Pomeroy, James W
    University of Bristol.
    Hilton, Keith P
    QinetiQ Ltd.
    Maclean, Jessica O
    QinetiQ Ltd.
    Wallis, David J
    QinetiQ Ltd.
    Uren, Michael J
    QinetiQ Ltd.
    Martin, Trevor
    QinetiQ Ltd.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lossy, Richard
    Ferdinand Braun Institute Hochstfrequenztech.
    Pazirandeh, Reza
    Ferdinand Braun Institute Hochstfrequenztech.
    Brunner, Frank
    Ferdinand Braun Institute Hochstfrequenztech.
    Wuerfl, Joachim
    Ferdinand Braun Institute Hochstfrequenztech.
    Kuball, Martin
    University of Bristol.
    Reducing Thermal Resistance of AlGaN/GaN Electronic Devices Using Novel Nucleation Layers2009In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 30, no 2, p. 103-106Article in journal (Refereed)
    Abstract [en]

    Currently, up to 50% of the channel temperature in AlGaN/GaN electronic devices is due to the thermal-boundary resistance (TBR) associated with the nucleation layer (NL) needed between GaN and SiC substrates for high-quality heteroepitaxy. Using 3-D time-resolved Raman thermography, it is shown that modifying the NL used for GaN on SiC epitaxy from the metal-organic chemical vapor deposition (MOCVD)-grown standard AIN-NL to a hot-wall MOCVD-grown AIN-NL reduces NL TBR by 25%, resulting in similar to 10% reduction of the operating temperature of AlGaN/GaN HEMTs. Considering the exponential relationship between device lifetime and temperature, lower TBR NLs open new opportunities for improving the reliability of AlGaN/GaN devices.

1 - 30 of 30
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf