Browsing by Author "Luong, Tien-Tung"

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2H-Silicon Carbide Epitaxial Growth on c-Plane Sapphire Substrate Using an AlN Buffer Layer and Effects of Surface Pre-Treatments
(2015-05-01)
Luong, Tien-Tung
;
Binh Tinh Tran
;
Ho, Yen-Teng
;
Wei, Ting-Wei
;
Wu, Yue-Han
The effects of surface pre-treatments and the role of an AN buffer layer for 2H-SiC growth on c-plane sapphire substrates by thermal CVD are investigated. While the crystallinity of SiC directly grown on sapphire substrate always degrades with a hydrogen pre-treatment but improves by optimizing carbonization, the crystallinity of SiC grown on sapphire substrate using an AN buffer grown by MOCVD improves with sufficient time of exposure to the H pre-treatment but always deteriorates with carbonization. Detailed microstructural analysis by phi-scan x-ray diffraction reveals that SiC film grown on sapphire substrate consists of crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60 degrees. A highly oriented hexagonal 2H-SiC film is obtained on low-cost c-plane sapphire substrate by using an AN buffer. 2H-SiC is unambiguously determined not only by phi-scan x-ray diffraction but also by high-resolution transmission electron microscopy. The growth relationship between 2H-SiC and 2H-AlN are coherent due to the favorable bonding of C and Al between SiC and AlN.
Characterizations of GaN Films Grown on Si (111) Substrates with Various Growth Temperatures of Multiple AlN Buffer Layers
(2012)
Binh-Tinh Tran
;
Chang, Edward Yi
;
Lin, Kung-Liang
;
Luong, Tien-Tung
;
Yu, Hung-Wei
We present the effect of multiple AlN buffer layers on characterizations of GaN film quality, which includes a thin high-low-high-temperature (HLHT) AlN buffer layers. The study is based on two different thicknesses of the GaN films on the buffers and found that the HLHT AlN buffer layers could significantly affect on the GaN films qualities. The buffer plays a very important role for the growth of GaN film on Si (111) substrate. The GaN film with an uniformly faceted surface and very high-quality has been obtained at the optimized multiple HLHT AlN buffer layers of 50-nm-thick at 1010-800-1010 degrees C.
Effect of Graded AlxGa1-xN Layers on the Properties of GaN Grown on Patterned Si Substrates
(2012-02-01)
Hsiao, Yu-Lin
;
Lu, Lung-Chi
;
Wu, Chia-Hsun
;
Chang, Edward Yi
;
Kuo, Chien-I
2.2-mu m-thick crack-free GaN films were grown on patterned Si substrates. The crack-free GaN films were obtained by patterning Si substrate and optimizing the graded AlxGa1-xN layers. With the increase of the graded AlxGa1-xN layer thickness, the GaN crystal quality improved as judged from the X-ray diffraction data. By applying multi-AlxGa1-xN layers on the patterned Si substrate, a 31% reduction of tensile stress for the GaN film was obtained as measured by micro-Raman. For the AlGaN/GaN high electron mobility transistor grown on 1 x 1 cm(2) larger patterns, the device exhibits maximum drain current density of 776 mA/mm and maximum transconductance of 101 mS/mm. (c) 2012 The Japan Society of Applied Physics
Effects of Al(x)Ga(1-x)N interlayer for GaN epilayer grown on Si substrate by metal-organic chemical-vapor deposition
(2010-05-01)
Lin, Kung-Liang
;
Chang, Edward-Yi
;
Hsiao, Yu-Lin
;
Huang, Wei-Ching
;
Luong, Tien-Tung
GaN film grown on Si substrate using multilayer AlN/Al(x)Ga(1-x)N buffer is studied by the low-pressure metal-organic chemical-vapor deposition method. The Al(x)Ga(1-x)N films with Al composition varying from 1 to 0.66 were used to accommodate the stress induced between GaN and the Si substrate during GaN growth. The correlation of the Al composition in the Al(x)Ga(1-x)N films with respect to the stress induced in the GaN film grown was studied using high-resolution x-ray diffraction, including symmetrical and asymmetrical omega/2 theta scans and reciprocal space maps. It is found that with proper design of the Al composition in the Al(x)Ga(1-x)N buffer layer, crack-free GaN film can be successfully grown on 6 in. Si (111) substrates using multilayer AlN and Al(x)Ga(1-x)N buffer layers. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3385672]
Electrical Properties of Compound 2D Semiconductor Mo1-xNbxS2
(2018-01-01)
Lu, Peng
;
Ho, Yen Teng
;
Chu, Yung-Ching
;
Zhang, Ming
;
Chien, Po-Yen
In order for TMD such as molybdenum disulfide (MoS2) to be useful for semiconductor industry, a controllable doping process is required. MoS2 with substitutional Nb shows a p-type behavior compared to the n-type characteristics of nominal films. In this work, the role of Nb in MoS2 will be examined, and a precise hole concentration control technique is demonstrated. Multi-layered Mo1-xNbxS2 samples with accurately controlled Nb mole fraction are synthesized. Electrical characterization and material analysis are performed to quantify the impact of Nb with mole fraction from 3.5% to 11%. The effective carrier concentration (p) and the ective hole mobility (mu(eff)) are found to be highly non-linear with respect to Nb mole fraction. Scanning Tunneling Microscope (STM) shows that the bandgap of the 2D transition metal dichalcogenide (TMD) is reduced by high mole fraction Nb. Therefore, Mo1-xNbxS2 can be considered as a compound TMD semiconductor.
Fabrication and characterization of n-In0.4Ga0.6N/p-Si solar cell
(2012-07-01)
Tran, Binh-Tinh
;
Chang, Edward-Yi
;
Trinh, Hai-Dang
;
Lee, Ching-Ting
;
Sahoo, Kartika Chandra
Electro-optic characteristics of a fabricated n-In0.4Ga0.6N/p-Si hetero-structure solar cell on Si substrate with Al and ITO (or Ti/Al/Ni/Au) materials for p and n-type contacts were investigated in this letter. The solar cell devices with ITO as n-type contacts were also compared to the solar cell using Ti/Al/Ni/Au as n-type contact in this study. High short-circuit current density observed for solar cell with ITO as n-type contacts due to the increased amount of light reaching the solar cell. The device with ITO contact exhibited an open-circuit voltage (V-oc) of 1.52 V and a short-circuit current density (J(sc)) of 8.68 mA/cm(2) with 54% fill factor. The conversion and external quantum efficiency (EQE) of the solar cell were 7.12 and 20.8%, respectively. Besides, a relationship between V-oc and In content in the InxGa1-xN alloys for this type of solar cell was also derived. (C) 2012 Elsevier B.V. All rights reserved.
Growth and Fabrication of AlGaN/GaN HEMT on SiC Substrate
(2012-01-01)
Wong, Yuen-Yee
;
Chiu, Yu-Sheng
;
Luong, Tien-Tung
;
Lin, Tai-Ming
;
Ho, Yen-Teng
AlGaN/GaN high electron mobility transistor (HEMT) was grown on silicon carbide substrate by metalorganic chemical vapor deposition technique. The AlGaN/GaN structure was optimized by tuning the growth conditions such as AlN buffer thickness, and the Al composition and thickness of AlGaN barrier layer. As a result, the X-ray rocking curve widths were 277 arcsec and 324 arcsec for the GaN (002) and (102) planes, respectively, indicating a high crystalline quality. Hall measurement showed that the AlGaN/GaN structure has a high electron mobility of 1840 (cm(2)/V-s) and a sheet electron concentration of 9.85 x10(12) cm-(2). Besides, HEMT device with sub-micron gate-length (0.7 mu m) was also successfully fabricated. DC measurement showed that the HEMT device has a saturated current of 800 mA/mm, a transconductance of 257 mS/mm and an off-state breakdown voltage larger than 100 V. For RF performance, the device has achieved an output power density (P-out), gain, and power added efficiency (PAE) of 7 W/mm, 23.5 dB and 61.7%, respectively, measured at 2 GHz frequency. On the other hand, the RF performance measured at 8 GHz showed that the device could achieve P-out, gain and PAE of 5.01 W/mm, 14.9 dB and 26.23% respectively.
Layered MoS2 grown on c-sapphire by pulsed laser deposition
(2015-03-01)
Ho, Yen-Teng
;
Ma, Chun-Hao
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Luong, Tien-Tung
;
Wei, Lin-Lung
;
Yen, Tzu-Chun
Layered growth of molybdenum disulphide (MoS2) was successfully achieved by pulsed laser deposition (PLD) method on c-plane sapphire substrate. Growth of monolayer to a few monolayer MoS2, dependent on the pulsed number of excimer laser in PLD is demonstrated, indicating the promising controllability of layer growth. Among the samples with various pulse number deposition, the frequency difference (A1gE12g) in Raman analysis of the 70 pulse sample is estimated as 20.11 cm(1), suggesting a monolayer MoS2 was obtained. Two-dimensional (2D) layer growth of MoS2 is confirmed by the streaky reflection high energy electron diffraction (RHEED) patterns during growth and the cross-sectional view of transmission electron microscopy (TEM). The in-plane relationship, (0006) sapphire//(0002) MoS2 and inline image sapphire//inline imageMoS(2) is determined. The results imply that PLD is suitable for layered MoS2 growth. Additionally, the oxide states of Mo 3d core level spectra of PLD grown MoS2, analysed by X-ray photoelectron spectroscopy (XPS), can be effectively reduced by adopting a post sulfurization process. (C) 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim
POST SULFURIZATION EFFECT ON THE MOS2 GROWN BY PULSED LASER DEPOSITION
(2016)
Ho, Yen-Teng
;
Yen, Tzu-Chun
;
Luong, Tien-Tung
;
Wei, Lin-Lung
;
Tu, Yung-Yi
Two inches size with high quality layered growth of MoS2 was achieved by PLD on c-plane sapphire substrate. 2-3 monolayer MoS2 was obtained within 2 inches wafer estimated from Raman analysis and confirmed by cross-sectional view of TEM. Additionally, the oxide states of Mo 3d core level spectra of MoS2, analyzed by XPS, can be effectively reduced by adopting a post sulfurization process in H2S. The post process also improve the photoluminescence (PL) of MoS2 as well as the electrical characteristic of MoS2 FET due to elimination the Mo oxide in the grown film.
WAFER SIZE MOS2 WITH FEW MONOLAYER SYNTHESIZED BY H2S SULFURIZATION
(2017-01-01)
Ho, Yen-Teng
;
Chu, Yung-Ching
;
Wei, Lin-Lung
;
Luong, Tien-Tung
;
Lin, Chih-Chien
Wafer sized, high quality continuous fihns would be a key demand for MoS2 implemented in circuit application. In this study, the growth of few monolayer Mo-S2 on 4 inches SiO2/Si substrate were demonstrated. The MoS2 thin films were synthesized by sulfurized in a furnace from the ultra-thin MoO3 starting materials by using H2S. The obtained MoS2 thin film examined by Raman analysis and Photoluminescence (PL), shows the semiconductor nature with direct transition peaks of 1.86 eV and 1.99 eV. The 4 5 monolayer of MoS2 with thickness around 2.6 nm is confirmed by cross-sectional view of transmission electron microscopy (TEM). Additionally, the DC characteristics of MoS2 MOSFETs exhibit at least 2 order in on/off current ratio, demonstrating the feasibility for circuit application.