Browsing by Author "Wen, TC"

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A dopant-related defect in Te-doped AlInP
(1999-08-01)
Wu, YR
;
Sung, WJ
;
Wen, TC
;
Lee, SC
;
Lee, WI
A deep level in Te-doped Al0.5In0.5P, grown by metal organic chemical vapor deposition, has been studied by deep level transient spectroscopy. The thermal activation energy was 0.24 eV, and the trap concentration was related to Te-dopant concentration. The deep level concentration strongly increased with elevating Te-dopant concentration. Meanwhile, the trap distribution profile also presented the same distribution behavior as the Te concentration profile. Therefore, the deep level in Te-doped AlInP is verified to be a dopant-related defect.
Activation of p-type GaN in a pure oxygen ambient
(2001-05-15)
Wen, TC
;
Lee, SC
;
Lee, WI
;
Chen, TY
;
Chan, SH
In this study, we activated p-type GaN in a pure oxygen ambient by rapid thermal annealing. The sheet resistance of p-type GaN was greatly reduced from > 10(7) Omega/square to 7.06 x 10(4) Omega/square after annealing in oxygen ambient at 500 degreesC, The photoluminescence intensity of blue emission increased by one order of magnitude compared to the as-grown sample. Moreover, the sheet resistance of p-type GaN annealed in pure oxygen ambient is lower than that of p-type GaN annealed in nitrogen ambient. The carrier concentrations of the samples annealed in oxygen ambient are higher than those annealed in nitrogen ambient. The better activation of p-type GaN in oxygen ambient is due to the higher activity of oxygen than that of nitrogen. Oxygen would remove hydrogen that passivates Ma atoms by forming H2O at a lower temperature.
Characteristics of optical properties of the interrupt growth method on InGaN/GaN MQW structures
(2000)
Lin, CF
;
Shu, CK
;
Lee, WH
;
Wen, TC
;
Chu, CF
The growth method and material properties of InGaN/GaN multiple quantum well (MQW) structures were studied in this experiment. The InGaN/GaN-MQW structure were deposited above the 2 mum-thick high quality GaN layers (with background carrier concentration was about 3.2 x 10(16) cm(-3)) on Al2O3 substrates. The interrupt growth time was 10 sec between GaN barrier layer and InGaN well growth at 690 degreesC. The stronger intensity and sharper photoluminescence (PL) spectra was observed from the interrupt growth MQW structures. The mean deviation of the PL peak position was lower than 1% by using the interrupt growth MQW structures at difference growth temperature. The PL spectra was become broaden and weaker by reducing the interrupt time during InGaN/GaN growth. The thickness of one pair InGaN/GaN was also identified by DCX-ray measurement and the growth rate InGaN layer was also calculated in this experiment.
Characterization of p-type InxGa1-xN grown by metalorganic chemical vapor deposition
(2001-03-01)
Wen, TC
;
Lee, WI
;
Sheu, JK
;
Chi, GC
;
友訊交大聯合研發中心
This study investigates the electrical and optical characteristics of Mg-doped InxGa1-xN grown by metalorganic chemical vapor deposition. All the Mg-doped InxGa1-xN layers show p-type conduction after thermal annealing. Room temperature (RT) carrier concentration increases exponentially with an In mole fraction increase. The highest hole concentration of bull; Mg-doped InxGa1-xN is 1.65 x 10(19) cm(-3). Also, the RT photoluminescence (PL) spectra of Mg related emissions in InxGa1-xN are displayed. However, the PL peak intensity becomes weak after the post-annealing process on Mg-doped InxGa1-xN. This degradation might be created by the surface dissociation during the post-annealing process. (C) 2001 Elsevier Science Ltd. All rights reserved.
Influence of barrier growth temperature on the properties of InGaN/GaN quantum Well
(2001-09-01)
Wen, TC
;
Lee, WI
;
電子物理學系
;
友訊交大聯合研發中心
;
Department of Electrophysics
In this study we investigate the effect of barrier growth temperature on the properties of InGaN/GaN multiple quantum wells. Double-crystal X-ray diffraction of MQW structures indicates that increasing the barrier growth temperature will reduce the well thickness. However, the photoluminescence peak wavelength shift is greater than the change of in the effective bandgap due to the reduction of well width. In addition to the reduction of well width, the determination of the origin of the significant blue shift in the photoluminescence peak wavelength should also take the strain effect into account.
Influence of barrier growth temperature on the properties of InGaN/GaN quantum wells
(2001)
Wen, TC
;
Lee, SC
;
Lee, WI
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
This study invests the effect of barrier growth temperature on the properties of InGaN/GaN MQW. Increase the growth temperature will reduce the well thickness and result in the blue shift of the PL peak. This blue shift in FL peak wavelength may be resulted from the stain occure during varying barrier growth temperature rather than only the reduce the well width. Moreover, we introduce a phase separation enhance layer into InGaN/GaN MQW. This layer join with the variation of barrier growth temperature will enhance the phase separation in InGaN/GaN MQW. There are two peaks clearly revealed in RT PL spectra. The higher energy peak might originate the InGaN quasi-wetting layer on the GaN barrier surface. The other one is interpreted of localize state at potential fluctuation owning to phase separation.
Liquid phase deposited SiO2 on GaN
(2003-04-29)
Wu, HR
;
Lee, KW
;
Nian, TB
;
Chou, DW
;
Wu, JJH
An efficient and low cost approach to deposit uniform silicon dioxide layers on GaN by liquid phase deposition (LPD) near room temperature are described and discussed. The process is simple. GaN wafers are immersed into a H2SiF6 and H3BO3 solution to form the silicon dioxide layers. The deposition conditions and the properties of the SiO2 films will be characterized. (C) 2002 Elsevier Science B.V. All rights reserved.
Observation of dislocation etch pits in epitaxial lateral overgrowth GaN by wet etching
(2002-04-01)
Wen, TC
;
Lee, WI
;
Sheu, JK
;
Chi, GC
;
電子物理學系
This work investigates dislocation etch pits in epitaxial lateral overgrowth (ELO) GaN by wet etching. A mixture of H2SO4 and H3PO4 was used as an etching solution. SEM and AFM were employed to observe the surface topography. For the as-grown sample, SEM images show the flat, smooth surface without any pits or hillocks. After the chemical etching, hexagonal shaped etch pits were observed at the edge of ELO GaN. AFM observation of etched ELO GaN displayed high densities of etch pits clustered in the "window" region and the coalescent line of two growing fronts. In contrast, the overgrowth region was nearly free of etch pits. Moreover, we observed that different sizes of etch pits dominated in "window" region and coalescent region. This implied different types dislocations dominated in these regions. (C) 2002 Elsevier Science Ltd. All rights reserved.
Phosphorus vacancy as a deep level in AlInP layers
(2000-06-15)
Sung, WJ
;
Wu, YR
;
Lee, SC
;
Wen, TC
;
Li, TJ
Deep levels in AlInP layers, grown by metal-organic chemical vapor deposition (MOCVD) with various V/III mole ratios, have been carefully investigated by deep-level transient spectroscopy (DLTS). A deep level originating from phosphorus vacancy was observed with the activation energy of 0.65 eV. Examining this phosphorus-vacancy-related deep level provided a relatively simple means of understanding the phosphorus vacancy in AlInP, thus allowing us to determine an appropriate V/III mole ratio for growing AlInP.
Study of a common deep level in GaN
(1999)
Wen, TC
;
Lee, SC
;
Lee, WI
;
Guo, JD
;
Feng, MS
A deep level with the activation energy around 0.45 similar to 0.6eV has persistently appeared in GaN samples grown by hydride vapor-phase epitaxy, organometallic vapor-phase epitaxy and molecular beam epitaxy. However, the origin of this deep level still remains unclear. In this study, we investigated this deep level trap E2 of GaN films by using deep level transient spectroscopy. The GaN films were grown by a conventional low pressure organometallic vapor-phase epitaxy technique with different V/III ratios. Frequency-dependent capacitance measurement was performed to determine the most proper frequency for capacitance measurements Capacitance-voltage measurements were then applied to obtain the carrier concentrations. The carrier concentration became higher as the flow rate of NH3 got lower. The deep level E2 is found in GaN samples grown with higher V/III ratios. The trap concentration of level E2 increased with increasing NH3 flow rate. Compared with the theoretical prediction of the nitrogen antisite level in GaN, the level E2 was believed to be related to nitrogen antisites.