Browsing by Author "Ou, J"

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A high-temperature thermodynamic model for metalorganic vapor phase epitaxial growth of InGaN
(1999-09-01)
Ou, J
;
Pan, YC
;
Lee, WH
;
Shu, CK
;
Lin, HC
A thermodynamic analysis tailored with a high-temperature parameter was performed for metalorganic vapor phase epitaxial (MOVPE) growth of InxGa1-xN alloys. Accordingly, a series of InGaN samples were prepared under various input In flow rates and growth temperatures. Theoretical results indicate that the In solid concentration tends to increase with increasing In flow rate and with decreasing temperature, whereas the metal droplets form more easily on the surface at lower growth temperatures and higher In fluxes, which are in good agreement with our experimental data.
An elucidation of solid incorporation of InGaN grown by metalorganic vapor phase epitaxy
(1998-06-01)
Ou, J
;
Chen, WK
;
Lin, HC
;
Pan, YC
;
Lee, MC
We carried out a systematic study on the solid incorporation of InGaN under various growth conditions using metalorganic vapor phase epitaxy (MOVPE). The solid distribution of InGaN was found to be very sensitive to the growth temperature, and the TMGa and TMIn flow rates. Experimental results indicated that at low Ga flow rates InGaN growth is essentially governed by thermodynamic factors, whereas at high growth rate the InGaN solid concentration is determined merely by the vapor composition in the gas phase. In regard to the effect of TMIn flow rates on InGaN growth, it was found that once In droplets form on the surface, the In growth efficiency correspondingly decreases significantly; accounting for the low In solid concentration in InGaN at high TMIn flow rates.
Crystalline structure changes in GaN films grown at different temperatures
(1997-05-15)
Lin, HC
;
Ou, J
;
Chen, WK
;
Chen, WH
;
Lee, MC
Thin GaN films were grown on (0001) sapphire at various temperatures between 520 and 1050 degrees C using metalorganic chemical vapor deposition (MOCVD). Optical properties and crystalline structures of the films were investigated by means of photoluminescence, Raman scattering, and X-ray diffraction. A noticeable structure transition occurred at around 750 degrees C with higher growth temperatures favoring the hexagonal structure and lower ones the cubic. Defect formation was also seen to be temperature dependent. The yellow luminescence which was clearly observed in our 700-850 degrees C films was attributable to the cubic and hexagonal structure mixing. The drastic reduction of yellow luminescence and the substantial enhancement of near band edge emission in the 950-1050 degrees C films indicated that this temperature range is optimum for growing high quality wurtzite films.
Growth and X-ray characterization of an InN film on sapphire prepared by metalorganic vapor phase epitaxy
(1997-12-15)
Chen, WK
;
Pan, YC
;
Lin, HC
;
Ou, J
;
Chen, WH
We report the successful growth of an InN film by metalorganic vapor phase epitaxy. The film quality is found to be strongly dependent on the growth temperature and the TMIn reactant flow rate. The best quality epilayer was obtained at 375 degrees C under a high V/III ratio growth environment. It exhibits a FWHM of the X-ray rocking curve as narrow as 96 arcsec: which explains the superior crystalline quality of our epitaxial film.
Growth and X-ray characterization of an InN film on sapphire prepared by metalorganic vapor phase epitaxy
(1997-12-15)
Chen, WK
;
Pan, YC
;
Lin, HC
;
Ou, J
;
Chen, WH
We report the successful growth of an InN film by metalorganic vapor phase epitaxy. The film quality is found to be strongly dependent on the growth temperature and the TMIn reactant flow rate. The best quality epilayer was obtained at 375 degrees C under a high V/III ratio growth environment. It exhibits a FWHM of the X-ray rocking curve as narrow as 96 arcsec: which explains the superior crystalline quality of our epitaxial film.
Influence of As/Al and Sb/Al gas flow ratios on growth of AlAs1-xSbx alloys
(1995-12-01)
Chen, WK
;
Ou, J
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
AlAs1-xSbx epilayers were grown on InP (100) substrates using the metalorganic chemical vapor epitaxial growth technique. Experimental results demonstrate that the solid concentration of AlAsSb is more naturally expressed as a function of the input As/Al partial pressure ratio, and not of the V/III ratio or the Sb mole fraction in group V used during the growth. In fact, the AlAs solid concentration and the input partial pressure ratio of As to Al are proportional to each other. According to the phase diagram described above, the controllability of the solid concentration of AlAsSb could be improved.
Isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition
(1999-08-03)
Shu, CK
;
Ou, J
;
Lin, HC
;
Chen, WK
;
Lee, MC
The isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition was investigated by using Raman scattering, scanning electron microscopy (SEM), and x-ray and photoluminescence (PL) measurements. In our study, the phonon spectra of films remain sharp without alloy formation after incorporation of small amounts of In atoms. The SEM pictures of the sample surface reveal greatly reduced nanopits indicating better surface flatness that is also supported by the multiple interference effect in the PL signals. More importantly, isoelectronic doping has caused the linewidth at 15 K of the near-band-edge emission of GaN to decrease sharply to 10 meV or less, reflecting improved optical property. (C) 1998 American Institute of Physics. [S0003-6951(98)01331-X].
Isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition
(1998-08-03)
Shu, CK
;
Ou, J
;
Lin, HC
;
Chen, WK
;
Lee, MC
The isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition was investigated by using Raman scattering, scanning electron microscopy (SEM), and x-ray and photoluminescence (PL) measurements. In our study, the phonon spectra of films remain sharp without alloy formation after incorporation of small amounts of In atoms. The SEM pictures of the sample surface reveal greatly reduced nanopits indicating better surface flatness that is also supported by the multiple interference effect in the PL signals. More importantly, isoelectronic doping has caused the linewidth at 15 K of the near-band-edge emission of GaN to decrease sharply to 10 meV or less, reflecting improved optical property. (C) 1998 American Institute of Physics.
Negative differential resistance in InGaAs/AlAsSb/InGaAs single-barrier heterostructure
(1997-09-08)
Chen, WK
;
Cheng, RH
;
Ou, J
;
交大名義發表
;
電子物理學系
We have observed negative differential resistance in InP lattice-matched InGaAs/AlAsSb/InGaAs single-barrier tunneling heterostructure. With a 10-nm-thick barrier, the diode exhibits a peak-to-valley current ratio of 4.2 (1.2) and peak current density of 54 (158) A/cm(2) at 100 K(300 K). (C) 1997 American Institute of Physics.
Optical and electrical investigations of isoelectronic In-doped GaN films
(2000)
Shu, CK
;
Lee, WH
;
Pan, YC
;
Chen, CC
;
Lin, HC
The optical and electrical properties of isoelectronic In-doped GaN films grown by metalorganic vapor phase epitaxy (MOVPE) were investigated by X-ray, photoluminescence (PL), Hall and Raman measurements. As a result, adequate In-doping quantity causes not only a reduction of yellow luminescence and unintentional background concentration, but an enhanced mobility and decrease in the widths. The improved crystalline and optical qualities of GaN films may be attributed to the decrease in defects. (C) 2000 Elsevier Science Ltd. All rights reserved.
Photoluminescence studies of GaN films of different buffer layer and doping concentration
(1998-02-01)
Shen, CC
;
Shu, CK
;
Lin, HC
;
Ou, J
;
Chen, WK
Photoluminescence (PL) measurements of GaN films with various buffer thicknesses and Si-doping concentrations have been carried out. PL response of one specific sample was studied for temperature dependence. The results showed that the band gap energy reduction is linearly proportional to the temperature increase with a slope of similar to-4 x 10(-4) eV.K-1 and that the activation energies for donor-bound and acceptor-bound exciton transitions are 15 and 18 meV, respectively. In Si-doped GaN films, the PL data indicated that the reduced gap depends on the third power of carrier concentration as n(1/3). We also obtained a concentration coefficient of 2.34 x 10(-4) eV.cm and a band gap energy of 3.426 eV in the undoped GaN film.
Photoluminescence studies of GaN films of different buffer layer and doping concentration
(1998-02-01)
Shen, CC
;
Shu, CK
;
Lin, HC
;
Ou, J
;
Chen, WK
Photoluminescence (PL) measurements of GaN films with various buffer thicknesses and Si-doping concentrations have been carried out. PL response of one specific sample was studied for temperature dependence. The results showed that the band gap energy reduction is linearly proportional to the temperature increase with a slope of similar to-4 x 10(-4) eV.K-1 and that the activation energies for donor-bound and acceptor-bound exciton transitions are 15 and 18 meV, respectively. In Si-doped GaN films, the PL data indicated that the reduced gap depends on the third power of carrier concentration as n(1/3). We also obtained a concentration coefficient of 2.34 x 10(-4) eV.cm and a band gap energy of 3.426 eV in the undoped GaN film.
Raman and X-ray studies of InN films grown at different temperatures by metalorganic vapor phase epitaxy
(1998-09-01)
Chen, WK
;
Lin, HC
;
Pan, YC
;
Ou, J
;
Shu, CK
We used Raman scattering and X-ray diffraction (XRD) methods to investigate the properties of InN films deposited at temperatures ranging from 325 to 600 degrees C by metalorganic vapor phase epitaxy (MOVPE). Significant line broadening, softening and intensity evolution were observed from films at growth temperatures between 375 and 450 degrees C. This can be attributed to the formation of mixed hexagonal and cubic structures and related dislocation defects. As the growth temperature was further increased, the hexagonal phase tvas found to be dominant in the deposited InN film.
Raman and x-ray studies of InN films grown by metalorganic vapor phase epitaxy
(1998-11-02)
Lee, MC
;
Lin, HC
;
Pan, YC
;
Shu, CK
;
Ou, J
Thin InN films were deposited on the (0001) sapphire substrate at various temperatures from 325 to 600 degrees C by metalorganic vapor phase epitaxy. We used Raman scattering and x-ray diffraction to investigate the film properties and crystalline structures. Significant line broadening, softening and intensity evolution were observed at the growth temperatures between 375 and 450 degrees C. This can be attributed to the formation of the mixed hexagonal and cubic structures and the related dislocation defects. As the growth temperature is further increased, the hexagonal phase is found to be dominant in the deposited InN film. (C) 1998 American Institute of Physics. [S0003-6951(98)00744-X].
Raman scattering in ternary AlAsxSb1-x films
(1998)
Lin, HC
;
Ou, J
;
Hsu, CH
;
Chen, WK
;
Lee, MC
Thin films of the ternary AlAsxSb1-x alloys, prepared by metalorganic chemical vapor deposition, were studied by Raman scattering. The Raman shifts show one-mode behavior and the forbidden TO phonon scattering is observable due to the relaxed selection rule. Our results of the mixed compounds can be interpreted using the spatial correlation model. Moreover, the enhanced scattering was observed at 2.15 and 2.8 eV which are attributable to the E-0 and E-1 transitions of AlAs and AlSb. (C) 1998 Elsevier Science Ltd. All rights reserved.
The effects of isoelectronic in-doping in GaN films grown by MOCVD
(1998)
Shu, CK
;
Ou, J
;
Lin, HC
;
Pan, YC
;
Lee, WH
The isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition (MOCVD) was investigated by using Raman scattering, scanning electron microscopy (SEM), Hall, Xray and photoluminescence (PL) measurements. In our study, after incorporating small amounts of In atoms into GaN compound (less than 0.4%, thus no alloy), SEM pictures showed improved surface smoothness with greatly reduced nano-pits, which was also confirmed by the multiple interference effects in PL spectra. Doping of adequate quantity caused the reduction of yellow luminescence and unintentional background concentration, and the line width shrinkage in X-ray, PL and Raman data, and the enhanced mobility. The improved crystalline and optical qualities of GaN:In films may be attributed to the decrease in dislocation density that may be related to the "impurity softening" phenomena.
Thermal stability study of Ni/Ta n-GaN Schottky contacts
(2002-01-28)
Chen, GL
;
Chang, FC
;
Shen, KC
;
Ou, J
;
Chen, WH
The Schottky behavior of Ni/Ta and Ni contacts on n-GaN was investigated under various annealing conditions by current-voltage measurements. It is found that with the addition of Ta between the Ni layer and the GaN substrate the thermal stability properties of devices can be significantly improved. Experimental results indicate that a high quality Ni/Ta n-GaN Schottky diode with an ideality factor and barrier height of 1.16 and 1.24 eV, respectively, can be obtained under 1 h annealing, at 700 degreesC. (C) 2002 American Institute of Physics.