Browsing by Author "Chiu, Yu-Sheng"

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An 80 nm In(0.7)Ga(0.3)As MHEMT with Flip-Chip Packaging for W-Band Low Noise Applications
(2010-01-01)
Wang, Chin-Te
;
Kuo, Chien-I
;
Lim, Wee-Chin
;
Hsu, Li-Han
;
Hsu, Heng-Tung
The fabrication process of an 80 nm In(0.7)Ga(0.3)As MHEMT device with flip-chip packaging on Al(2)O(3) substrate is presented. The flip-chip packaged device exhibited good dc characteristics with high I(DS) = 425 mA/mm and high g(m) = 970 mS/mm at V(DS) = 1.5 V. Besides, the RF performances revealed high gain of 10 dB at 50 GHz and low minimum noise figure (NF(min))below 2 dB at 60 GHz, showing the feasibility of flip-chip packaged In(0.7)Ga(0.3)As MHEMT device for low noise applications at W-band.
An 80 nm In0.7Ga0.3As MHEMT with Flip-Chip Packaging for W-Band Low Noise Applications
(2010-01-01)
Wang, Chin-Te
;
Kuo, Chien-, I
;
Lim, Wee-Chin
;
Hsu, Li-Han
;
Hsu, Heng-Tung
The fabrication process of an 80 nm In0.7Ga0.3As MHEMT device with flip-chip packaging on Al2O3 substrate is presented. The flip-chip packaged device exhibited good dc characteristics with high I-DS = 425 mA/mm and high g(m) = 970 mS/mm at V-DS = 1.5 V. Besides, the RF performances revealed high gain of 10 dB at 50 GHz and low minimum noise figure (NFmin)below 2 dB at 60 GHz, showing the feasibility of flip-chip packaged In0.7Ga0.3As MHEMT device for low noise applications at W-band.
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.
Performance Improvements of AlGaN/GaN HEMTs by Strain Modification and Unintentional Carbon Incorporation
(2015-03-01)
Tien-Tung Luong
;
Binh Tinh Tran
;
Ho, Yen-Teng
;
Minh-Thien-Huu Ha
;
Hsiao, Yu-Lin
An advanced AlGaN/GaN HEMT structure, grown on a sapphire substrate by MOCVD utilizing a high temperature (HT) AN interlayer (IL) and a multilayer high-low-high temperature (HLH) AN buffer layer, demonstrates a superior performance both in breakdown voltage (>200 V) and maximum drain current (Ipss = 667 mA/mm). The HT AN IL produces an additional compressive strain into the above GaN layer. Accordingly, an AlGaN barrier, grown on the more compressive GaN, introduces less tensile strain leading to an improvement in surface morphology (RMS = 0.19 nm in 2 x 2 mu m(2)), a remarkable increase in 2DEG mobility by 46% (mu(S)= 1900 cm(2)/Vs) and a decrease in densities of defects acting as paths for the leakage current through the AlGaN barrier. A high semi-insulating buffer is achieved by eliminating leakage paths both through the buffer layer and the buffer-substrate interfacial layer. These result from an increase in unintentional carbon introduced by AIN layers, especially by a low temperature AN layer; which are grown under low pressure (50 Ton). Lastly, the decrease in AlGaN barrier tensile strain and low leakage current in the advanced HEMTs structure using an HT AN IL and an HLH AIN buffer are promising for an improvement in AlGaN/GaN HEMTs\' reliability.
RF Characteristics of AlGaN/GaN HEMTs under Different Temperatures
(2012-01-01)
Chiu, Yu-Sheng
;
Huang, Jui-Chien
;
Lin, Tai-Ming
;
Chou, Yu-Ting
;
Lu, Chung-Yu
We present the Rf characteristics of 0.7-mu m gate length n-GaN/AlGaN/GaN high-electron mobility transistors (HEMTs) with different source-drain spacing tested under different temperatures.. The 7-mu m source-drain spacing device demonstrated 800 mA/mm drain current density and 257 mS/mm tranceconductance, and the 5-mu m source-drain spacing device demonstrated 700 mA/mm drain current density and 260 mS/mm tranconductance. The 7-mu m source-drain spacing device was measured at room temperatures of 25 degrees C and -40 degrees C, the current gain (f(T)) were 18 GHz and 21GHz and the maximum oscillation (f(max)(U)) frequency were 63 GHz-and 87 GHz, respectively The f(T) was nearly linearly dependent on the temperature. As operating temperature increased from -40 degrees C to 50 degrees C, the f(T) dropped more dramatically for the 5-mu m SD spacing device than for the 7-mu m device. The f(max) characteristic of 5-mu m SD spacing device decreases more dramatically above 125 degrees C than the 7-mu m SD spacing device. This phenomenon might be due to stronger phonon scattering for shorter channel device at high temperatures.
The Circle-grid Electrode on Concentrated GaAs Solar Cells Efficiency
(2011)
Chung, Chen-Chen
;
Yu, Hung-Wei
;
Hsu, Li-Han
;
Kuo, Chien-I
;
Nguyen-Hong Quan
The relationship between front contact pattern of GaAs single-junction solar cell with conversion efficiency at different concentration ratios is studied in this paper. Five different front circle-grid patterns were designed and patterned on the in-house fabricated single junction GaAs solar cells. At high light concentration ratio, the cell efficiency is strongly dependent on the series resistance of the electrode. At the same time, the thermal effect should also be taken into consideration, especially when a device is operating under high concentration ratio. Therefore, the aim of this work is to find a suitable front contact pattern for a GaAs single-junction solar cell to increase the conversion efficiency under high concentration solar radiation. It is found that the device with proper pattern design geometrical shadowing factor of 7.1% has the best cell efficiency of 27.05% at CR>100x, AM1.5G.
Ti/Al/Ti/Ni/Au ohmic contacts on AlGaN/GaN high electron mobility transistors with improved surface morphology and low contact resistance
(2014-01-01)
Chiu, Yu-Sheng
;
Lin, Tai-Ming
;
Nguyen, Hong-Quan
;
Weng, Yu-Chen
;
Nguyen, Chi-Lang
Optimizing surface morphology of ohmic contacts on GaN high electron mobility transistors continues to be a challenge in the GaN electronics industry. In this study, a variety of metal schemes were tested under various annealing conditions to obtain contacts with optimal qualities. A Ti/Al/Ti/Ni/Au (20/120/40/60/50 nm) metal scheme demonstrated the lowest contact resistance (R-c) and a smooth surface morphology, and the mechanisms were investigated by materials analysis. A Ti/Al/Ti/Ni/Au metal scheme with optimized Ti and Ni thicknesses can result in formation of a larger proportion of Al-Ni intermetallics and a continuous TiN interlayer, which results in smooth surface and low R-c. (C) 2014 American Vacuum Society.