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Hsu, Chih-Wei
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Publications (10 of 19) Show all publications
Minamisawa, R. A., Mihaila, A., Farkas, I., Teodorescu, V. S., Afanasev, V. V., Chih-Wei, C.-W., . . . Rahimo, M. (2016). Characterization of a n+3C/n-4H SiC heterojunction diode. Applied Physics Letters, 108(14), 143502
Open this publication in new window or tab >>Characterization of a n+3C/n-4H SiC heterojunction diode
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2016 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 14, p. 143502-Article in journal (Refereed) Published
Abstract [en]

We report on the fabrication of n+3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to similar to 7 x 10(17) cm(-3) dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extracted from CV measurement. We finally compare the electrical results of the n+3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices. (C) 2016 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-127776 (URN)10.1063/1.4945332 (DOI)000374230700040 ()
Available from: 2016-05-12 Created: 2016-05-12 Last updated: 2017-11-30
Chen, J.-T., Hsu, C.-W., Forsberg, U. & Janzén, E. (2015). Metalorganic chemical vapor deposition growth of high-mobility AlGaN/AlN/GaN heterostructures on GaN templates and native GaN substrates. Journal of Applied Physics, 117(8), Article ID 085301.
Open this publication in new window or tab >>Metalorganic chemical vapor deposition growth of high-mobility AlGaN/AlN/GaN heterostructures on GaN templates and native GaN substrates
2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, article id 085301Article in journal (Refereed) Published
Abstract [en]

Severe surface decomposition of semi-insulating (SI) GaN templates occurred in high-temperature H2 atmosphere prior to epitaxial growth in a metalorganic chemical vapor deposition system. A two-step heating process with a surface stabilization technique was developed to preserve the GaN template surface. Utilizing the optimized heating process, a high two-dimensional electron gas mobility ∼2000 cm2/V·s was obtained in a thin AlGaN/AlN/GaN heterostructure with an only 100-nm-thick GaN spacer layer homoepitaxially grown on the GaN template. This technique was also demonstrated viable for native GaN substrates to stabilize the surface facilitating two-dimensional growth of GaN layers. Very high residual silicon and oxygen concentrations were found up to ∼1 × 1020 cm−3 at the interface between the GaN epilayer and the native GaN substrate. Capacitance-voltage measurements confirmed that the residual carbon doping controlled by growth conditions of the GaN epilayer can be used to successfully compensate the donor-like impurities. State-of-the-art structural properties of a high-mobility AlGaN/AlN/GaN heterostructure was then realized on a 1 × 1 cm2 SI native GaN substrate; the full width at half maximum of the X-ray rocking curves of the GaN (002) and (102) peaks are only 21 and 14 arc sec, respectively. The surface morphology of the heterostructure shows uniform parallel bilayer steps, and no morphological defects were noticeable over the entire epi-wafer.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-117135 (URN)10.1063/1.4913223 (DOI)000351132500059 ()
Note

The authors would like to acknowledge the support from the Swedish Foundation for Strategic Research.

Available from: 2015-04-17 Created: 2015-04-17 Last updated: 2017-12-04Bibliographically approved
Chen, J.-T., Persson, I., Nilsson, D., Hsu, C.-W., Palisaitis, J., Forsberg, U., . . . Janzén, E. (2015). Room-Temperature mobility above 2200 cm2/V.s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure. Applied Physics Letters, 106(25), Article ID 251601.
Open this publication in new window or tab >>Room-Temperature mobility above 2200 cm2/V.s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure
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2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 25, article id 251601Article in journal (Refereed) Published
Abstract [en]

A high mobility of 2250 cm2/V·s of a two-dimensional electron gas (2DEG) in a metalorganic chemical vapor deposition-grown AlGaN/GaN heterostructure was demonstrated. The mobility enhancement was a result of better electron confinement due to a sharp AlGaN/GaN interface, as confirmed by scanning transmission electron microscopy analysis, not owing to the formation of a traditional thin AlN exclusion layer. Moreover, we found that the electron mobility in the sharp-interface heterostructures can sustain above 2000 cm2/V·s for a wide range of 2DEG densities. Finally, it is promising that the sharp-interface AlGaN/GaN heterostructure would enable low contact resistance fabrication, less impurity-related scattering, and trapping than the AlGaN/AlN/GaN heterostructure, as the high-impurity-contained AlN is removed.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-117133 (URN)10.1063/1.4922877 (DOI)000357036600005 ()
Available from: 2015-04-17 Created: 2015-04-17 Last updated: 2017-12-04Bibliographically approved
Lundskog, A., Hsu, C.-W., Karlsson, K. F., Amloy, S., Nilsson, D., Forsberg, U., . . . Janzén, E. (2014). Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots. Light: Science & Applications, 3, Article ID e139.
Open this publication in new window or tab >>Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots
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2014 (English)In: Light: Science & Applications, ISSN 2095-5545, Vol. 3, article id e139Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2014
Keywords
GaN; InGaN; photoluminescence; polarized emission; quantum dot
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-97417 (URN)10.1038/lsa.2014.20 (DOI)000331998400011 ()
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2017-04-11Bibliographically approved
Jemsson, T., Machhadani, H., Karlsson, F. K., Hsu, C.-W. & Holtz, P.-O. (2014). Linearly polarized single photon antibunching from a site-controlled InGaN quantum dot. Applied Physics Letters, 105(8), 081901-1-081901-4
Open this publication in new window or tab >>Linearly polarized single photon antibunching from a site-controlled InGaN quantum dot
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2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 8, p. 081901-1-081901-4Article in journal (Refereed) Published
Abstract [en]

We report on the observation of linearly polarized single photon antibunching in the excitonic emission from a site-controlled InGaN quantum dot. The measured second order coherence function exhibits a significant dip at zero time difference, corresponding to g(m)(2) (0) = 0: 90 under continuous laser excitation. This relatively high value of g(m)(2) (0) is well understood by a model as the combination of short exciton life time (320 ps), limited experimental timing resolution and the presence of an uncorrelated broadband background emission from the sample. Our result provides the first rigorous evidence of InGaN quantum dot formation on hexagonal GaN pyramids, and it highlights a great potential in these dots as fast polarized single photon emitters if the background emission can be eliminated.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112065 (URN)10.1063/1.4893476 (DOI)000342753500022 ()
Note

Funding Agencies|Carl Trygger Foundation for Scientific Research; Swedish Research Council (VR); Nano-N consortium - Swedish Foundation for Strategic Research (SSF); Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Font-D, at Linkoping University

Available from: 2014-11-17 Created: 2014-11-13 Last updated: 2017-12-05Bibliographically approved
Lundskog, A., Hsu, C.-W., Nilsson, D., Karlsson, K. F., Forsberg, U., Holtz, P.-O. & Janzén, E. (2013). Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD. Journal of Crystal Growth, 363, 287-293
Open this publication in new window or tab >>Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD
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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
Holtz, P. O., Hsu, C.-W., Lundskog, A., Karlsson, K. F., Forsberg, U. & Janzén, E. (2013). Deterministic Single InGaN Quantum Dots grown on GaN Micro-Pyramid Arrays. Paper presented at 2012 International Conference on Nano Materials and Electric Devices (ICNMED 2012), 19-20 December 2012, Hong Kong. Advanced Materials Research, 646, 34-37
Open this publication in new window or tab >>Deterministic Single InGaN Quantum Dots grown on GaN Micro-Pyramid Arrays
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2013 (English)In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 646, p. 34-37Article in journal (Other academic) Published
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.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2013
Keywords
Quantum dots, Pyramid, Exciton, Photoluminescence
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-111502 (URN)10.4028/www.scientific.net/AMR.646.34 (DOI)
Conference
2012 International Conference on Nano Materials and Electric Devices (ICNMED 2012), 19-20 December 2012, Hong Kong
Available from: 2014-10-20 Created: 2014-10-20 Last updated: 2017-12-05Bibliographically approved
Hsu, C.-W. (2013). InGaN Quantum Dots Grown on GaN Pyramid Arrays. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>InGaN Quantum Dots Grown on GaN Pyramid Arrays
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Selective-area growth (SAG) of InGaN on GaN pyramids, which allows the formation of additional hybrid quantum structures, including quantum wires and quantum dots (QDs) in a site-controlled fashion, is attractive for both fundamental research and device application. The site-controlled growth of QDs showing sharp emission lines is seen as the first step toward the frontier quantum information application (QIA). Note that, in such case, one QD represents one device unless the challenge of fabricating identical QDs is overcome.

The concept of SAG GaN pyramids hosting InGaN QDs has been reported since 2000. However, the observation of sharp emission lines, which can be ascribed to three-dimensional carrier confinement in QDs, seems to be occasional.

The main outcome of this work is the investigation of the InGaN QDs grown on GaN hexagonal pyramids. This work covers the formation mechanism of InGaN QDs to the emission properties of individual InGaN QDs. A modified SAG approach to obtain InGaN QDs emitting photons with heralded polarization directions is also demonstrated. The inherent high polarization degree of photons emitted by InGaN QDs together with heralded polarization direction reveals a promising potential for the direct generation of linearly-polarized photons by site-controlled InGaN QDs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. p. 59
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1534
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-97412 (URN)978-91-7519-550-6 (ISBN)
Public defence
2013-09-05, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2013-09-16Bibliographically approved
Hsu, C.-W., Moskalenko, E., Eriksson, M., Lundskog, A., Karlsson, F. K., Forsberg, U., . . . Holtz, P.-O. (2013). The charged exciton in an InGaN quantum dot on a GaN pyramid. Applied Physics Letters, 103(1)
Open this publication in new window or tab >>The charged exciton in an InGaN quantum dot on a GaN pyramid
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2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 1Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-95961 (URN)10.1063/1.4812984 (DOI)000321497200036 ()
Note

Funding Agencies|NANO-N consortium||Swedish Foundation for Strategic Research (SSF)||

Available from: 2013-08-19 Created: 2013-08-12 Last updated: 2017-12-06
Masuda, R., Hsu, C.-W., Eriksson, M., Kumagai, Y., Koukitu, A. & Holtz, P.-O. (2012). Improvements in Optical Properties of (0001) ZnO Layers Grown on (0001) Sapphire Substrates by Halide Vapor Phase Epitaxy Using Thick Buffer Layers. Japanese Journal of Applied Physics, 51(3), 031103
Open this publication in new window or tab >>Improvements in Optical Properties of (0001) ZnO Layers Grown on (0001) Sapphire Substrates by Halide Vapor Phase Epitaxy Using Thick Buffer Layers
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2012 (English)In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 51, no 3, p. 031103-Article in journal (Refereed) Published
Abstract [en]

The optical properties of (0001) ZnO layers grown at 1000 degrees C on (0001) sapphire substrates by halide vapor phase epitaxy (HVPE) were investigated by various photoluminescence (PL) measurements. A layer grown with a H2O/ZnCl2 (VI/II) ratio of 20 on a 0.4-mu m-thick buffer layer exhibited a significant near-band-edge (NBE) peak blueshift and degraded internal quantum efficiency (eta(int)) due to residual compressive stress. Growth with a VI/II ratio of 600 diminished the NBE peak blueshift; however, deep level emission and a reduction of PL decay time (tau(PL)) were caused by point defects generated by excess O source supply. A layer without the NBE peak blueshift and deep level emission was realized by growth with a VI/II ratio of 20 and a buffer layer of 0.8 mu m. The eta(int) and tau(PL) for HVPE-grown layers could be improved to 4.1% and 122.8 ps by using the thick buffer layer and appropriate VI/II ratio.

Place, publisher, year, edition, pages
Japan Society of Applied Physics, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-76529 (URN)10.1143/JJAP.51.031103 (DOI)000301348400011 ()
Note

Funding Agencies|Tokyo University of Agriculture and Technology||Japan Society for the Promotion of Science||

Available from: 2012-04-12 Created: 2012-04-11 Last updated: 2017-12-07
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