Browsing by Author "Lin, Tai-Ming"

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Growth and Fabrication of AlGaN/GaN HEMT on SiC Substrate
(2012-01-01)
Wong, Yuen-Yee
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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.
RF Characteristics of AlGaN/GaN HEMTs under Different Temperatures
(2012-01-01)
Chiu, Yu-Sheng
;
Huang, Jui-Chien
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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.
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
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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.