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  • 1.
    Alvi, Naveed ul Hassan
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Mohammad, Riaz
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Tzamalis, Georgios
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nour, Omer
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fabrication and characterization of high-brightness light emitting diodes based on n-ZnO nanorods grown by a low-temperature chemical method on p-4H-SiC and p-GaN2010In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 25, no 6, p. 065004-Article in journal (Refereed)
    Abstract [en]

    Light emitting diodes (LEDs) based on n-ZnO nanorods (NRs)/p-4H-SiC and n-ZnO (NRs)/p-GaN were fabricated and characterized. For the two LEDs the ZnO NRs were grown using a low temperature (andlt;100 degrees C) aqueous chemical growth (ACG) technique. Both LEDs showed very bright nearly white light electroluminescence (EL) emission. The observed luminescence was a result of the combination of three emission lines composed of violet-blue, green and orange-red peaks observed from the two LEDs. Room temperature photoluminescence (PL) was also measured and consistency with EL was observed. It was found that the green and violet-blue peaks are red-shifted while the orange peak is blue-shifted in the EL measurement. It was also found that due to the effect of the GaN substrate the violet-blue peak in the EL measurement is more red-shifted in n-ZnO (NRs)/p-GaN LEDs as compared to n-ZnO (NRs)/p-4H-SiC LEDs.

  • 2.
    Bano, Nargis
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hussain Ibupoto, Zafar
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nour, Omer
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Klason, P
    Gothenburg University.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Study of luminescent centers in ZnO nanorods catalytically grown on 4H-p-SiC2009In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 24, no 12, p. 125015-Article in journal (Refereed)
    Abstract [en]

    High-quality ZnO nanorods (NRs) were grown by the vapor-liquid-solid (VLS) technique on 4H-p-SiC substrates. Heterojunction light emitting diodes (LEDs) were fabricated. Electrical characterization including deep level transient spectroscopy (DLTS) complemented by photoluminescence (PL) is used to characterize the heterojunction LEDs. In contrast to previously published results on n-ZnO thin films on p-SiC, we found that the dominant emission is originating from the ZnO NRs. Three luminescence lines have been observed; these are associated with blue (465 nm) and violet (446 nm) emission lines from ZnO NRs emitted by direct transition/recombination of carriers from the conduction band to a zinc vacancy (V-Zn) radiative center and from a zinc interstitial (Zn-i) radiative center to the valance band. The third green-yellow (575 nm) spectral line is emitted due to a transition of carriers from Zn-i to V-Zn. The superposition of these lines led to the observation of strong white light which appears as a wide band in the room temperature PL.

  • 3.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Tu, C. W.
    Magneto-optical and light-emission properties of III-As-N semiconductors2002In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 17, no 8, p. 815-822Article in journal (Refereed)
    Abstract [en]

    A brief review on our present knowledge of optical and magneto-optical properties of III-V-N alloys, in particular, Ga(In)NAs alloys with low nitrogen compositions is given. The main attention is focused on fundamental electronic parameters of the Ga(In)NAs alloys as well as key material-related issues which are relevant to device applications, such as identification of dominant recombination processes in the alloys, compositional dependence of electron effective mass and band alignment in Ga(In)NAs-based heterostructures.

  • 4.
    David, Denis
    et al.
    Universidade Federal da Bahia, Campus Ondina, Salvador-Ba, Brazil.
    Alnoor, Hatim
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Mancir da Silva Santana, Victor
    Universidade Federal da Bahia, Campus Ondina, Salvador-Ba, Brazil.
    Bargiela, Pascal
    Royal Institute of Technology, Stockholm, Sweden.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Baldissera, Gustavo
    Royal Institute of Technology, Stockholm, Sweden.
    Persson, Clas
    Royal Institute of Technology, Stockholm, Sweden; University of Oslo, Oslo, Norway.
    Ferreira da Silva, Antonio
    Universidade Federal da Bahia, Campus Ondina, Salvador-Ba, Brazil.
    Optical properties from photoelectron energy-loss spectroscopy of low-temperature aqueous chemically synthesized ZnO nanorods grown on Si2019In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 34, no 4, article id 045019Article in journal (Refereed)
    Abstract [en]

    The optical properties of zinc oxide (ZnO) nanorods (NRs) synthesized by the low-temperature aqueous chemical method on top of silicon (Si) substrate have been investigated by means of photoelectron energy loss spectroscopy (PEELS). The ZnO NRs were obtained by the low temperature aqueous chemical synthesis on top of Si substrate. The measured valence band, the dynamical dielectric functions and optical absorption of the material show a reasonable agreement when the trending and shape of the theoretical calculations are considered. A first-principle calculation based on density functional theory (DFT) was performed using the partially self-consistent GW approximation (scGW0) and compared to the experimental results. The application of these two techniques brings a new analysis of the electronic properties of this material. The experimental results regarding the density of states (DOS) obtained for the valence band using x-ray photoelectron spectroscopy (XPS) was found to be consistent with the theoretical calculated value. Due to this consistency, the same wavefunctions was then employed to calculate the dielectric function of the ZnO NRs. The experimentally extracted dielectric function was also consistent with the calculated values.

  • 5.
    Echresh, Ahmad
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology. Shahid Chamran University of Ahvaz, Iran.
    Abbasi, Mazhar Ali
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Zargar Shoushtari, Morteza
    Shahid Chamran University of Ahvaz, Iran.
    Farbod, Mansoor
    Shahid Chamran University of Ahvaz, Iran.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Optimization and characterization of NiO thin film and the influence of thickness on the electrical properties of n-ZnO nanorods/p-NiO heterojunction2014In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 29, no 11, p. 115009-Article in journal (Refereed)
    Abstract [en]

    In this study, we report on the synthesis optimization of NiO thin film to grow preferentially along the (111) direction. The x-ray diffraction (XRD) pattern revealed that the NiO film with 200 nm thickness annealed at 600 degrees C temperature has the best preferential orientation along the (111) direction. Also, atomic force microscope (AFM) images show that the grain size of NiO increases at higher temperatures. Then, ZnO nanorods were grown on the NiO thin film with 100, 200 and 300 nm thickness grown at 600 degrees C. The XRD pattern and scanning electron microscope (SEM) images indicate that the well-aligned ZnO nanorods with hexagonal face have a preferential orientation along the c-axis (002). The current voltage measurements of the n-ZnO nanorods/p-NiO heterojunctions showed a clear rectifying behavior for all diodes. The threshold voltage of the heterojunctions was increased by increasing the thickness of the NiO thin film which was attributed to the increasing of the series resistance (R-s) of the diodes.

  • 6. Ewing, D.J.
    et al.
    Porter, L.M.
    Wahab, Qamar Ul
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ciechonski, Rafal
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Inhomogeneous electrical characteristics in 4H-SiC Schottky diodes2007In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 22, no 12, p. 1287-1291Article in journal (Refereed)
    Abstract [en]

    Hundreds of current-voltage (I-V) measurements of Ni, Pt and Ti Schottky diodes on 4H-SiC were conducted at low applied voltages. The SiC substrates contained homoepitaxial layers grown by either chemical vapor deposition or sublimation. While near-ideal contacts were fabricated on all samples, a significant percentage of diodes (∼7%-50% depending on the epitaxial growth method and the diode size) displayed a non-ideal, or inhomogeneous, barrier height. These 'non-ideal' diodes occurred regardless of growth technique, pre-deposition cleaning method, or contact metal. In concurrence with our earlier reports in which the non-ideal diodes were modeled as two Schottky barriers in parallel, the lower of the two Schottky barriers, when present, was predominantly centered at one of the three values: ∼0.60, 0.85 or 1.05 eV. The sources of these non-idealities were investigated using electron-beam- induced current (EBIC) and deep-level transient spectroscopy (DLTS) to determine the nature and energy levels of the defects. DLTS revealed a defect level that corresponds with the low- (non-ideal) barrier height, at ∼0.60 eV. It was also observed that the I-V characteristics tended to degrade with increasing deep-level concentration and that inhomogeneous diodes tended to contain defect clusters. Based on the results, it is proposed that inhomogeneities, in the form of one or more low-barrier height regions within a high-barrier height diode, are caused by defect clusters that locally pin the Fermi level. © 2007 IOP Publishing Ltd.

  • 7.
    Filippov, Stanislav
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Ishikawa, F.
    Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan.
    Chen, Weimin M
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Structural properties of GaNAs nanowires probed by micro-Raman spectroscopy2016In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 31, no 2, article id 025002Article in journal (Refereed)
    Abstract [en]

    GaNAs-based nanowires (NWs) form a novel material system of potential importance for applications in advanced optoelectronic and photonic devices, thanks to the advantages provided by band-structure engineering, one-dimensional architecture and the possibility to combine them with mainstream silicon technology. In this work we utilize the micro-Raman scattering technique to systematically study the structural properties of such GaAs/GaNAs core/shell NW structures grown by molecular beam epitaxy on a Si substrate. It is shown that the employed one-dimensional architecture allows the fabrication of a GaNAs shell with a low degree of alloy disorder and weak residual strain, at least within the studied range of nitrogen (N) compositions [N] < 0.6%. Raman scattering by the GaAs-like and GaN-like phonons is found to be enhanced when the excitation energy approaches the E + transition energy. Since this effect is found to be more pronounced for the GaN-like phonons, the involved intermediate states are concluded to be localized in proximity to N impurities, i.e. they likely represent N-related cluster states located in proximity to E + .

  • 8.
    Florentin, M.
    et al.
    IMB CNM CSIC C Tillers, Spain.
    Cabello, M.
    IMB CNM CSIC C Tillers, Spain.
    Rebollo, J.
    IMB CNM CSIC C Tillers, Spain.
    Montserrat, J.
    IMB CNM CSIC C Tillers, Spain.
    Brosselard, P.
    CALY Technology, France.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Godignon, P.
    IMB CNM CSIC C Tillers, Spain.
    Al-implanted on-axis 4H-SiC MOSFETs2017In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 3, article id 035006Article in journal (Refereed)
    Abstract [en]

    In this paper, the impact of temperature and time stress on gate oxide stability of several multi-implanted and epitaxied 4H-SiC nMOSFET is presented. The oxide layer was processed under a rapid thermal process (RTP) furnace. The variation of the main electrical parameters is shown. We report the high quality and stability of such implanted MOSFETs, and point out the very low roughness effect of the on-axis-cut sample. Particularly, in the best case, effective channel mobility (mu(fe)) overcomes 20 cm(2). V-1. s(-1) at 300 degrees C for a channel length of 12 mu m, which is very encouraging for implantation technology. Starting from 200 degrees C, the apparent increase of the mu(fe) peak of the MOSFET ceases and tends to saturate with further temperature increase. This is an indication of the potential of MOSFETs built on on-axis substrates. Thus, starting from the real case of an implanted MOSFET, the global purpose is to show that the electrical performance of such an on-axis-built device can tend to reach that of the ideal case, i.e. epitaxied MOSFET, and even overcome its electrical limitation, e.g. in terms of threshold voltage stability at high temperature.

  • 9.
    Gogova, D.
    et al.
    Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin, Germany, Central Lab. of Solar Energy, Bulgarian Academy of Sciences, Blvd. Tzarigradsko shose 72, 1784 Sofia, Bulgaria.
    Siche, D.
    Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin, Germany.
    Fornari, R.
    Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin, Germany.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Gibart, P.
    LUMILOG, 2720, Chemin Saint Bernard, Les Moulins I, F-06220 Vallauris, France.
    Dobos, L.
    Research Institute for Technical Physics and Materials Science, Hungarian Academy of Science, 1121 Budapest, Hungary.
    Pecz, B.
    Pécz, B., Research Institute for Technical Physics and Materials Science, Hungarian Academy of Science, 1121 Budapest, Hungary.
    Tuomisto, F.
    Laboratory of Physics, Helsinki University of Technology, PO Box 1100, 02015 HUT, Finland.
    Bayazitov, R.
    Kazan Physical Technical Institute, Russian Academy of Sciences, Russian Federation.
    Zollo, G.
    Dipartimento di Energetica, University 'La Sapienza' of Rome, via A Scarpa 14-16, 00161 Rome, Italy.
    Optical and structural studies of high-quality bulk-like GaN grown by HVPE on a MOVPE AlN buffer layer2006In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 21, no 5, p. 702-708Article in journal (Refereed)
    Abstract [en]

    High-quality 400 ?m thick GaN has been grown by hydride vapour phase epitaxy (HVPE) on (0 0 0 1) sapphire with a 2 ?m thick AlN buffer layer. The material's crystalline quality and homogeneity was verified by x-ray diffraction (XRD), low-temperature photoluminesence (LT-PL) and LT cathodoluminescence. Plan-view transmission electron microscopy images reveal a low dislocation density of ~1.25 × 107 cm-2. The residual stress of the material was studied by two complementary techniques. LT-PL spectra show the main neutral donor bound exciton line at 3.4720 eV. This line position suggests virtually strain-free material with a high crystalline quality as indicated by the small full width at half maximum value of 0.78 meV. The presence of well resolved A- and B-free excitons in the LT-PL spectra and the absence of a yellow luminescence band prove the high quality of the HVPE-GaN in terms of purity and crystallinity. These findings are consistent with the XRD results, implying the high crystalline quality of the material grown. Hence, the material studied is well suited as a lattice parameter and thermal-expansion- coefficient matched substrate for further homoepitaxy, as needed for high-quality III-nitride device applications. Strain-free homoepitaxy on native substrates is needed to decrease considerably the defect density and in that way an improvement of the device's performance and lifetime can be achieved. © 2006 IOP Publishing Ltd.

  • 10.
    Izadifard, Morteza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Utsumi, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Furukawa, Y.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Wakahara, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Effects of rapid thermal annealing on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy2005In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 20, no 5, p. 353-356Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent photoluminescence (PL), PL excitation and time-resolved PL measurements were employed to study the effects of rapid thermal annealing (RTA) on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy. A substantial increase in radiative efficiency of GaNP epilayers, which is especially pronounced for the high-energy PL component, was achieved after RTA and is attributed to annealing out of competing non-radiative centres. The latter is evident from reduced quenching of the PL intensity with increasing measurement temperature, which results in a strong increase (up to 18 times) in the PL intensity at room temperature (RT), as well as from a substantial increase in carrier lifetime at RT deduced from time-resolved PL measurements.

  • 11.
    Jacob, A P
    et al.
    Chalmers .
    Myrberg, T
    Chalmers .
    Nour, Omer
    Chalmers .
    Willander, Magnus
    Chalmers.
    Lundgren, P
    Chalmers.
    Sveinbjörnsson, E Ö
    Chalmers.
    Ye, L L
    Chalmers.
    Thölen, A
    Chalmers.
    Caymax, M
    Interuniversity Microelectronics Centre (IMEC), Leuven, Belgium .
    Cryogenic performance of ultrathin oxide MOS capacitors with in situ doped p(+) poly-Si1-xGex and poly-Si gate materials2002In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 17, no 9, p. 942-946Article in journal (Refereed)
    Abstract [en]

    A low-temperature electrical characterization of ultrathin oxide MOS capacitors with p(+) poly-Si1-xGex and poly-Si gate is performed. The investigated structures are suitable for future nano-scaled high speed MOSFETs. The aim of this study is to compare the low-temperature performance of poly-Si1-xGex and poly-Si gate MOS structures in the nanoscale channel length regime. Apart from the significant change in the flat band voltage, the result shows that all the poly-Si and poly-Si1-xGex gated MOS structures exhibit two centres of polarity change (zero-temperature coefficients) in capacitance. The second polarity change leads to an exclusive phenomenon in these structures. The low-temperature capacitance is found to be less than high-temperature capacitance at strong accumulation and this is in contrast to what has been observed so far in metal-gated capacitors. It is also observed that the temperature dependence of the tunnelling current is only on the oxide thickness and not on the gate material used.

  • 12.
    Kassamakova, L.
    et al.
    Bulgarian Academy of Sciences, Plovdiv.
    Kakanakova-Georgieva, Anelia
    Bulgarian Academy of Sciences, Sofia.
    Kakanakov, R.
    Bulgarian Academy of Sciences, Plovdiv.
    Marinova, Ts.
    Bulgarian Academy of Sciences, Sofia.
    Kassamakov, I.
    Bulgarian Academy of Sciences, Plovdiv.
    Djambova, Tz.
    Bulgarian Academy of Sciences, Plovdiv.
    Noblanc, O.
    Thomson-CSF/LCR, Orsay Cédex, France .
    Arondo, C.
    Thomson-CSF/LCR, Orsay Cédex, France .
    Cassette, S.
    Thomson-CSF/LCR, Orsay Cédex, France .
    Brylinski, C.
    Thomson-CSF/LCR, Orsay Cédex, France .
    Thermostable Ti/Au/Pt/Ti Schottky contacts on n-type 4H-SiC1998In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 13, no 9, p. 1025-1030Article in journal (Refereed)
    Abstract [en]

    The electrical properties and interface chemistry of Ti/Au/Pt/Ti Schottky contacts to n-type 4H-SiC have been investigated with respect to their utilization for MESFETs operated at high temperatures. The electrical properties of these contacts were studied at room temperature as well as during thermal treatment. The barrier height determined from I-V characteristics was calculated to be 1.17 eV with an ideality factor of 1.09. These parameters were examined by ageing and temperature dependence tests as criteria for the thermal stability and reliability of the contacts. The barrier height and ideality factor did not change after prolonged heating at a constant temperature of and operating temperatures up to , which confirmed the contact stability. Diodes used in the measurements showed a low leakage current at 100 V reverse voltage and room temperature ( A) as well as at ( A) and breakdown voltage above 400 V.

    The chemical interface properties were studied by x-ray photoelectron spectroscopy for as-deposited, annealed and heated contacts. Annealing at for 10 min led to formation of TiC and in a restricted region close to the SiC interface. The data revealed a chemically stable Ti/SiC interface after annealing, which is of importance for stable rectifying characteristics during long-term operation.

  • 13.
    Khan, Azam
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain, Mushtaque
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Abbasi, Mazhar Ali
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain Ibupoto, Zafar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Study of transport properties of copper/zinc-oxide-nanorods-based Schottky diode fabricated on textile fabric2013In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 28, no 12, p. 125006-Article in journal (Refereed)
    Abstract [en]

    In this work, a copper/zinc-oxide (ZnO)-nanorods-based Schottky diode was fabricated on the textile fabric substrate. ZnO nanorods were grown on a silver-coated textile fabric substrate by using the hydrothermal route. Scanning electron microscopy and x-ray diffraction techniques were used for the structural study. The electrical characterization of copper/ZnO-nanorods-based Schottky diodes was investigated by using a semiconductor parameter analyzer and an impedance spectrometer. The current density-voltage (J-V) and capacitance-voltage (C-V) measurements were used to estimate the electrical parameters. The threshold voltage (V-th), ideality factor (eta), barrier height (phi(b)), reverse saturation current density (J(s)), carrier concentration (N-D) and built-in potential (V-bi) were determined by using experimental data and (simulated) curve fitting. This study describes the possible fabrication of electronic and optoelectronic devices on textile fabric substrate with an acceptable performance.

  • 14.
    Khomyak, V. V.
    et al.
    Fedkovich Chernivtsi National University, Ukraine.
    Ilashchuk, M. I.
    Fedkovich Chernivtsi National University, Ukraine.
    Shtepliuk, Ivan I.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. NAS Ukraine, Ukraine.
    Properties of p-n-junctions formed by a laser irradiation of a surface of n-Cd1-xZnx Te single crystal2015In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 30, no 3, article id 035016Article in journal (Refereed)
    Abstract [en]

    Photosensitive barrier structures were fabricated by high-power pulsed laser irradiation of a freshly-cleaved surface of n-type bulk Cd1-xZnxTe substrates. Their electrical properties were investigated and discussed. Dominant carrier mechanisms at a forward and a reverse bias in terms of a recombination and tunnel-recombination model were analyzed. At the illumination reaching 100 mW.cm(-2), these surface-barrier p-Cd1-xZnxTe/n-Cd1-xZnxTe structures were possessed by the following photoelectric parameters: open-circuit voltage V-oc = 0.61 V, short-circuit current I-sc = 0.21 mA and fill factor FF = 0.49, respectively.

  • 15.
    Lebedev, A.A.
    et al.
    Russian Academy of Sciences.
    Abramov, P.L.
    Russian Academy of Sciences.
    Bogdanova, E.V.
    Russian Academy of Sciences.
    Lebedev, S.P.
    Russian Academy of Sciences.
    Nelson, D.K.
    Russian Academy of Sciences.
    Oganesyan, G.A.
    Russian Academy of Sciences.
    Tregubova, A.S.
    Russian Academy of Sciences.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Highly doped p-type 3C-SiC on 6H-SiC substrates2008In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 23, no 7Article in journal (Refereed)
    Abstract [en]

    Highly doped p-3C-SiC layers of good crystal perfection have been grown by sublimation epitaxy in vacuum. Analysis of the photoluminescence spectra and temperature dependence of the carrier concentration shows that at least two types of acceptor centers at ∼EV + 0.25 eV and at EV + 0.06-0.07 eV exist in the samples studied. A conclusion is reached that layers of this kind can be used as p-emitters in 3C-SiC devices. © 2008 IOP Publishing Ltd.

  • 16.
    Lin, Yen-Ku
    et al.
    Natl Chiao Tung Univ, Taiwan.
    Bergsten, Johan
    Chalmers Univ Technol, Sweden.
    Leong, Hector
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Malmros, Anna
    Chalmers Univ Technol, Sweden.
    Chen, Jr-Tai
    SweGaN AB, Tekn Ringen 8D, SE-58330 Linkoping, Sweden.
    Chen, Ding-Yuan
    Chalmers Univ Technol, Sweden; SweGaN AB, Tekn Ringen 8D, SE-58330 Linkoping, Sweden.
    Kordina, Olof
    SweGaN AB, Tekn Ringen 8D, SE-58330 Linkoping, Sweden.
    Zirath, Herbert
    Chalmers Univ Technol, Sweden.
    Chang, Edward Yi
    Natl Chiao Tung Univ, Taiwan; Natl Chiao Tung Univ, Taiwan; Natl Chiao Tung Univ, Taiwan.
    Rorsman, Niklas
    Chalmers Univ Technol, Sweden.
    A versatile low-resistance ohmic contact process with ohmic recess and low-temperature annealing for GaN HEMTs2018In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 33, no 9, article id 095019Article in journal (Refereed)
    Abstract [en]

    Deeply recessed ohmic contacts for GaN-based high electron mobility transistors (HEMTs) are demonstrated. It is shown that low-resistance ohmic contacts can be achieved with recessing beyond the AlGaN Schottky barrier where the ohmic contacts are formed on the sidewall of the recess. This makes the process versatile and relatively insensitive to the exact recess depth. The ohmic contact is based on a gold-free metallization scheme consisting of a Ta/Al/Ta metal stack requiring a low-temperature annealing. Important parameters for this type of ohmic contact process include the metal coverage, slope of the etched sidewall, bottom Ta-layer thickness, as well as annealing temperature and duration. The optimized contact resistance is as low as 0.24 Omega mm after annealing at 575 degrees C. Moreover, this sidewall contact approach was successfully implemented on different epitaxial heterostructures with different AlGaN barrier thickness as well as with and without AlN exclusion layer. All the samples exhibited excellent contact resistances in a wide range of recess depths. The Ta-based, sidewall ohmic contact process is a promising method for forming an ohmic contact on a wide range of GaN HEMT epitaxial designs.

  • 17.
    Milanova, M.
    et al.
    Central Lab Appl Phys, Bulgaria.
    Donchev, V.
    Sofia University, Bulgaria.
    Kostov, K. L.
    Bulgarian Academic Science, Bulgaria.
    Alonso-Alvarez, D.
    Imperial Coll London, England.
    Valcheva, E.
    Sofia University, Bulgaria.
    Kirilov, K.
    Sofia University, Bulgaria.
    Asenova, I.
    Sofia University, Bulgaria.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Georgiev, S.
    Sofia University, Bulgaria.
    Ekins-Daukes, N.
    Imperial Coll London, England.
    Experimental study of the effect of local atomic ordering on the energy band gap of melt grown InGaAsN alloys2017In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 8, article id 085005Article in journal (Refereed)
    Abstract [en]

    We present a study of melt grown dilute nitride InGaAsN layers by x-ray photoelectron spectroscopy (XPS), Raman and photoluminescence (PL) spectroscopy. The purpose of the study is to determine the degree of atomic ordering in the quaternary alloy during the epitaxial growth at near thermodynamic equilibrium conditions and its influence on band gap formation. Despite the low In concentration (similar to 3%) the XPS data show a strong preference toward In-N bonding configuration in the InGaAsN samples. Raman spectra reveal that most of the N atoms are bonded to In instead of Ga atoms and the formation of N-centred In3Ga1 clusters. PL measurements reveal smaller optical band gap bowing as compared to the theoretical predictions for random alloy and localised tail states near the conduction band minimum.

  • 18.
    Miranda, Alonso L.
    et al.
    CINVESTAV, Mexico; University of Liege, Belgium.
    Xu, Bin
    University of Liege, Belgium; University of Arkansas, AR 72701 USA; University of Arkansas, AR 72701 USA.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Romero, Aldo H.
    CINVESTAV, Mexico; W Virginia University, WV 26506 USA.
    Verstraete, Matthieu J.
    University of Liege, Belgium.
    Ab initio calculation of the thermal conductivity of indium antimonide2014In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 29, no 12, p. 124002-Article in journal (Refereed)
    Abstract [en]

    A theoretical study based on the density functional theory and the temperature-dependent effective potential method is performed to analyze the changes in the phonon band structure as a function of temperature for indium antimonide. In particular, we show changes in the thermal expansion coefficient and the thermal resistivity that agree rather well with experimental measurements. From the theoretical side, we show a weak dependence with respect to the chosen thermostat used to obtain the inter-atomic force constants, which strengthens our conclusions.

  • 19.
    Muniza Faraz, Sadia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ashraf, H
    Applied Material Science, Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalsweg 135, 6525AJ Nijmegen, The Netherlands.
    Imran Arshad, M
    Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan.
    Hageman, P R
    Applied Material Science, Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalsweg 135, 6525AJ Nijmegen, The Netherlands.
    Asghar, M
    Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan.
    Ul Wahab, Qamar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Interface state density of free-standing GaN Schottky diodes2010In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 25, no 9, p. 095008-Article in journal (Refereed)
    Abstract [en]

    Schottky diodes were fabricated on the HVPE-grown, free-standing gallium nitride (GaN) layers of n- and p-types. Both contacts (ohmic and Schottky) were deposited on the top surface using Al/Ti and Pd/Ti/Au, respectively. The Schottky diode fabricated on n-GaN exhibited double barriers with values of 0.9 and 0.6 eV and better performance in the rectification factor together with reverse and forward currents with an ideality factor of 1.8. The barrier height for the p-GaN Schottky diode is 0.6 eV with an ideality factor of 4.16. From the capacitance-voltage (C-V) measurement, the net doping concentration of n-GaN is 4 x 10(17) cm(-3), resulting in a lower reverse breakdown of around -12 V. The interface state density (N-SS) as a function of E-C-E-SS is found to be in the range 4.23 x 10(12)-3.87 x 10(11) eV(-1) cm(-2) (below the conduction band) from Ec-0.90 to E-C-0.99. Possible reasons responsible for the low barrier height and high ideality factor have been addressed.

  • 20. Neimontas, K.
    et al.
    Malinauskas, T.
    Aleksiejunas, R.
    Sudzius, M.
    Jarasiunas, K.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    The determination of high-density carrier plasma parameters in epitaxial layers, semi-insulating and heavily doped crystals of 4H-SiC by a picosecond four-wave mixing technique2006In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 21, no 7, p. 952-958Article in journal (Refereed)
    Abstract [en]

    We applied a picosecond four-wave mixing technique for measurements of carrier lifetimes and diffusion coefficients in highly excited epitaxial layers, semi-insulating and heavily doped 4H-SiC substrates. Optical carrier injection at two different wavelengths (266 and 355 nm) allowed us to vary the depth of the excited region from 1-2 νm to 50 νm, and thus determine photoelectric parameters of carrier plasma in the density range from 2 × 1016 to 1019 cm-3. Strong dependence of carrier lifetime and mobility on carrier density was found in the epitaxial layers. The origin of fast decay components, not resolved previously by photoluminescence and free-carrier absorption techniques in SiC, was attributed to nonlinear carrier recombination. Numerical modelling provided a value of bimolecular recombination coefficient equal to B ≤ (2-4) × 10-11 cm3 s-1 and verified a surface recombination velocity S ≤ 4 × 104 cm s-1. In heavily doped crystals, nonlinear carrier recombination reduced the carrier lifetime down to 1.1 ns, while in semi-insulating ones a lifetime of 1.5-2.5 ns was measured. Temperature dependences of four-wave mixing provided monopolar carrier mobility in heavily doped and bipolar one in semi-insulating crystals, and revealed the contribution of ionized impurity and phonon scattering mechanisms. © 2006 IOP Publishing Ltd.

  • 21.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hai, P. N.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Ellison, A.
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Optically detected magnetic resonance studies of intrinsic defects in 6H-SiC1999In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 14, no 12, p. 1141-1146Article in journal (Refereed)
    Abstract [en]

     Optically detected magnetic resonance (ODMR) was used for study of defects in n-type 6H-SiC. Four ODMR spectra related to spin S = 1 centres were observed. Two of these centres, labelled a and b, have a trigonal symmetry with the symmetry axis along the c-axis of the hexagonal crystal. For the other two centres, labelled c and d, the symmetry is lower (C1h) and the principal axis z of the g- and D-tensor is about 71 degrees off the c-axis. Based on the symmetry axes, the annealing behaviour and the intensity, these spectra are suggested to originate from different configurations of the paired centre between a silicon vacancy and a nearest-neighbour point defect (either a carbon vacancy or a silicon antisite), occupying different inequivalent sites in the 6H-SiC. These defects are non-radiative and act as efficient recombination channels in the material.

  • 22.
    Nour, Eiman
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zinc oxide piezoelectric nano-generators for low frequency applications2017In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 6, article id 064005Article in journal (Refereed)
    Abstract [en]

    Piezoelectric Zinc Oxide (ZnO) nanogenerators (NGs) have been fabricated for low frequency (amp;lt;100 Hz) energy harvesting applications. Different types of NGs based on ZnO nanostructures have been carefully developed, and studied for testing under different kinds of low frequency mechanical deformations. Well aligned ZnO nanowires (NWs) possessing high piezoelectric coefficient were synthesized on flexible substrates using the low temperature hydrothermal route. These ZnO NWs were then used in different configurations to demonstrate different low frequency energy harvesting devices. Using piezoelectric ZnO NWs, we started with the fabrication of a sandwiched NG for a handwriting enabled energy harvesting device based on a thin silver layer coated paper substrate. Such device configurations can be used for the development of electronic programmable smart paper. Further, we developed this NG to work as a triggered sensor for a wireless system using footstep pressure. These studies demonstrate the feasibility of using a ZnO NWs piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks. After that, we investigated and fabricated a sensor on a PEDOT: PSS plastic substrate using a one-sided growth and double-sided growth technique. For the first growth technique, the fabricated NG has been used as a sensor for an acceleration system; while the fabricated NG by the second technique works as an anisotropic direction sensor. This fabricated configuration showed stability for sensing and can be used in surveillance, security, and auto-Mobil applications. In addition to that, we investigated the fabrication of a sandwiched NG on plastic substrates. Finally, we demonstrated that doping ZnO NWs with extrinsic elements (such as Ag) will lead to the reduction of the piezoelectric effect due to the loss of crystal symmetry. A brief summary into future opportunities and challenges is also presented.

  • 23.
    Ouacha, H.
    et al.
    Physics Department, Chalmers University of Technology, University of Gothenburg, S-412 96 Gothenburg, Sweden.
    Nur, O.
    Physics Department, Chalmers University of Technology, University of Gothenburg, S-412 96 Gothenburg, Sweden.
    Fu, Y.
    Physics Department, Chalmers University of Technology, University of Gothenburg, S-412 96 Gothenburg, Sweden.
    Willander, M.
    Physics Department, Chalmers University of Technology, University of Gothenburg, S-412 96 Gothenburg, Sweden.
    Ouacha, A.
    Turan, R.
    Physics Department, Middle East Technical University, 06531 Ankara, Turkey.
    Comparison between the noise properties of PtSi/p-Si1-xGex and Pt/p-Si1-xGex Schottky contacts prepared by co-sputtering and thermal reaction2001In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 16, no 4, p. 255-259Article in journal (Refereed)
    Abstract [en]

    The noise properties of Pt/p-Si1-xGex and PtSi/p-Si1-xGex (x = 0.14) Schottky contacts have been studied. The silicide layer PtSi was formed by thermal reaction (TR) of Pt with a silicon substrate and by co-sputtering (CS) of Pt and Si onto the strained Si1-xGex layer. The noise measurements were performed at temperature T = 77 K over the frequency range 10-104 Hz. Higher noise level was observed in the annealed diode Pt/p-Si1-xGex. In both diodes, the noise was found to exhibit 1/f behaviour and was attributed to fluctuations of the generation-recombination current at the interface states. The results reveal significant reductions in the total noise by 70%, and the interface state density Nit by three orders of magnitude when the silicide is formed by the CS process.

  • 24.
    Pecz, B.
    et al.
    Hungarian Academic Science, Hungary.
    Toth, L.
    Hungarian Academic Science, Hungary.
    Tsiakatouras, G.
    University of Crete, Greece; University of Crete, Greece.
    Adikimenakis, A.
    University of Crete, Greece.
    Kovacs, A.
    Forschungszentrum Julich, Germany.
    Duchamp, M.
    Forschungszentrum Julich, Germany.
    Dunin-Borkowski, R. E.
    Forschungszentrum Julich, Germany.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Neumann, P. L.
    Hungarian Academic Science, Hungary.
    Behmenburg, H.
    AIXTRON SE, Germany.
    Foltynski, B.
    AIXTRON SE, Germany.
    Giesen, C.
    AIXTRON SE, Germany.
    Heuken, M.
    AIXTRON SE, Germany.
    Georgakilas, A.
    University of Crete, Greece; University of Crete, Greece.
    GaN heterostructures with diamond and graphene2015In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 30, no 11, p. 114001-Article in journal (Refereed)
    Abstract [en]

    The full performance of GaN devices for high power applications is not exploited due to their self-heating. Possible solutions are the integration of materials with high heat conductivity i.e., single crystalline diamond and graphene layers. We report the growth of single crystalline (0001)-oriented GaN thin films on (100), (110) and (111) diamond single crystals studied by transmission electron microscopy (TEM) in cross-sections. As for graphene, we show a high quality GaN layer that was deposited on patterned graphene layers and 6H-SiC. The atomic structures of the interfaces in the heterostructure are studied using aberration-corrected scanning TEM combined with energy dispersive x-ray and electron energy-loss spectroscopy.

  • 25. Pidgeon, CR
    et al.
    Phillips, PJ
    Carder, D
    Murdin, BN
    Fromherz, T
    Paul, DJ
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Zhao, Ming
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Pump-probe measurement of lifetime engineering in SiGe quantum wells below the optical phonon energy2005In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 20, no 10, p. L50-L52Article in journal (Refereed)
    Abstract [en]

    We have directly determined with pump/probe spectroscopy the light hole (LH1) excited state lifetime for the lowest heavy hole to light hole intrawell subband transition (HH1-LH1) for three prototype samples of Si/SiGe strain-symmetrized multi-quantum well structures, designed to have the final LH1 state increasingly unconfined. The transition energy is below the optical phonon energy. We find that a decay time of 20 ps for sample 1 with a well width of 5.0 nm lengthens to 40 ps for sample 3 with a well width of 3.0 nm, in good agreement with the design. In addition, we have measured the lifetime for holes excited out of the well, from which we determine the lifetime for diagonal transitions (back into the well) to be of approx. several hundred picoseconds.

  • 26.
    Shtepliuk, Ivan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. NASU, Ukraine.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Combining graphene with silicon carbide: synthesis and properties - a review2016In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 31, no 11, p. 113004-Article, review/survey (Refereed)
    Abstract [en]

    Being a true two-dimensional crystal, graphene possesses a lot of exotic properties that would enable unique applications. Integration of graphene with inorganic semiconductors, e.g. silicon carbide (SiC) promotes the birth of a class of hybrid materials which are highly promising for development of novel operations, since they combine the best properties of two counterparts in the frame of one hybrid platform. As a specific heterostructure, graphene on SiC performs strongly, dependent on the synthesis method and the growth modes. In this article, a comprehensive review of the most relevant studies of graphene growth methods and mechanisms on SiC substrates has been carried out. The aim is to elucidate the basic physical processes that are responsible for the formation of graphene on SiC. First, an introduction is made covering some intriguing and not so often discussed properties of graphene. Then, we focus on integration of graphene with SiC, which is facilitated by the nature of SiC to assume graphitization. Concerning the synthesis methods, we discuss thermal decomposition of SiC, chemical vapor deposition and molecular beam epitaxy, stressing that the first technique is the most common one when SiC substrates are used. In addition, we briefly appraise graphene synthesis via metal mediated carbon segregation. We address in detail the main aspects of the substrate effect, such as substrate face polarity, off-cut, kind of polytype and nonpolar surfaces on the growth of graphene layers. A comparison of graphene grown on the polar faces is made. In particular, growth of graphene on Si-face SiC is critically analyzed concerning growth kinetics and growth mechanisms taking into account the specific characteristics of SiC (0001) surfaces, such as the step-terrace structure and the unavoidable surface reconstruction upon heating. In all subtopics obstacles and solutions are featured. We complete the review with a short summary and concluding remarks.

  • 27.
    Valakh, M.Ya.
    et al.
    Institute of Semiconductor Physics NASU, Kiev 03028, Ukraine.
    Ivanov, S.V.
    Ioffe Physico-Technical Institute, St. Petersburg 194021, Russian Federation.
    Mestres, N.
    Institut de Ciència de Materials de Barcelona (CSIC), Campus UAB, 08193 Bellaterra, Spain.
    Pascual, J.
    Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
    Shubina, T.V.
    Ioffe Physico-Technical Institute, St. Petersburg 194021, Russian Federation.
    Sorokin, S.V.
    Ioffe Physico-Technical Institute, St. Petersburg 194021, Russian Federation.
    Streltchuk, V.V.
    Institute of Semiconductor Physics NASU, Kiev 03028, Ukraine.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Optical investigation of CdSe/ZnSe quantum nanostructures2002In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 17, no 2, p. 173-177Article in journal (Refereed)
    Abstract [en]

    We have used resonant and non-resonant Raman scattering as well as photoluminescence and cathodoluminescence experiments to study the structure and composition properties of CdxZn1-xSe formed by migration enhanced epitaxy of CdSe layers on ZnSe buffers. The spectral change of the photoluminescence maximum correlates with the increase of the Cd content, depending on the nominal CdSe thickness in the 1.5-3.0 ML range. The inhomogeneous broadening of the photoluminescence band is caused by the composition difference between the two-dimensional mixed CdxZn1-xSe layer and the inserted islands with larger Cd concentration. This is confirmed by phonon frequency changes in resonant Raman scattering for samples with different nominal CdSe thicknesses as well as in Stokes and anti-Stokes frequency changes observed in the 1.5 ML sample. Attention is paid to the role of defects on Raman scattering and photoluminescence for the 3.15 ML sample.

  • 28.
    Zakharova, A.
    et al.
    Institute of Physics and Technology of the Russian Academy of Sciences, Nakhimovskii Avenue 34, Moscow 117218, Russian Federation.
    Semenikhin, I.
    Institute of Physics and Technology of the Russian Academy of Sciences, Nakhimovskii Avenue 34, Moscow 117218, Russian Federation.
    Chao, K.A.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Optical absorption of polarized light in InAs/GaSb quantum wells2008In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 23, no 12Article in journal (Refereed)
    Abstract [en]

    Using an eight-band k p model Hamiltonian with the Burt-Foreman envelope function theory, we have investigated the optical absorption of both linearly and circularly polarized light, as well as related phenomena in InAs/GaSb broken-gap quantum wells grown along the [0 0 1] direction, with emphasis on the effects of electron-hole hybridization and the various symmetry-breaking mechanisms such as structural inversion asymmetry, bulk inversion asymmetry and interface Hamiltonian. The optical matrix elements exhibit unusual angular dependence in close connection with the spin-flip transitions which are originally forbidden. The spin split of the 2e subband results in two profound absorption peaks for the 1hh-2e transition for both linearly polarized and circularly polarized light. A large lateral optical anisotropy appears in the absorption coefficient of linearly polarized light, which can reach almost 100% with a reducing thickness of the quantum well. For the absorption of circularly polarized light, we found a large enhancement of electron spin polarization in the upper 2e subband, which was generally considered as forbidden if the polarization is along the direction perpendicular to the plane-of-light incidence. © 2008 IOP Publishing Ltd.

  • 29.
    Zhao, H
    et al.
    Chalmers University.
    M Wang, S
    Chalmers University.
    Zhao, Qingxiang
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    H Lai, Z
    Chalmers University.
    Sadeghi, M
    Chalmers University.
    Larsson , A
    Chalmers University.
    Comparison of optical and structural quality of GaIn(N) As analog and digital quantum wells grown by molecular beam epitaxy2008In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 23, no 12, p. 125002-Article in journal (Refereed)
    Abstract [en]

    A set of Ga0.625In0.375(N) As single quantum well (QW) samples with the identical total amounts of Ga and In and QW thicknesses was designed and grown by both the analog and the digital methods using molecular beam epitaxy. The N exposure time in the GaInNAs samples was kept the same. The inter-band gap recombination in the analog and the digital InGaAs QWs appears in a similar transition energy range as a result of In segregation. Temperature-dependent photoluminescence (PL) measurements were performed on the GaInNAs samples. An S-shaped dependence of the transition energy on temperature was observed in the digital GaInNAs QWs but not in the analog GaInNAs QW. Post-growth rapid thermal annealing had remarkably different effects on the PL intensity: an increase for the analog InGaAs QW and for the analog and digital GaInNAs QWs, but a decrease for the digital InGaAs QW with increasing annealing temperature. The GaIn(N) As samples grown by the digital method showed weaker PL intensities and smaller wavelength blue-shifts than the similar samples grown by the analog method. Possible strain relaxation mechanisms are discussed.

1 - 29 of 29
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