This study proposes a ␦-doped InGaP/InGaAs/GaAs high-electron mobility transistor ͑HEMT͒ grown by a metallorganic chemical vapor deposition system. The wide-range temperature-dependent breakdown characteristics of the ␦-doped InGaP/InGaAs HEMT are studied. The two-terminal gate-source breakdown voltage of the proposed HEMT is as high as 70 V at 300 K. The drain current of the ␦-doped InGaP/InGaAs HEMT has low sensitivity to the measured temperature between 77 and 470 K. Furthermore, the proposed device sustains high voltages over 30 V within the temperature range 77-470 K.
As an alternative to AlGaAs/GaAs and InGaP/GaAs camel-gate heterostructure field-effect transistors ͑CAMFETs͒ for microwave applications, InAlGaP/GaAs/InGaAs pseudomorphic high-electron-mobility transistors ͑CAM-pHEMTs͒ are shown to have high breakdown voltage, high broad-plateau extrinsic transconductance ͑g m ͒, and small leakage current. Two-terminal gate-source breakdown voltage exceeding 20 V is achieved for CAM-pHEMT with Ni/Au gate metal. The transconductance curve is quite broad for a gate voltage range of approximately 3.6 V. Additionally, CAM-pHEMT exhibits relatively negligible temperaturedependent characteristics over the operating temperature range. Therefore, the studied device displays promise for hightemperature applications.
A cost effective EnhancementiDepletion mode pHEMT MMIC process on 6-inch GaAs wafer is demonstrated by using 0.5um gate-length optical stepper pHEMT technology. E-mode and D-mode gates are deposited simultaneously in this process simplification. The E-mode pHEMT exhibits a pinch-off voltage of +0.22V (defined at O.lmA/mm), and a maximum extrinsic transconductance of 400mS/mm at room temperature. The off-state current of E-mode device is typically O.lSuA/mm at Vgs=OV and Vds=3V. This current is extreme low and is suitable for high density digital circuits with minimized power consumption. On the other hand, a pinch-off voltage of -0.7SV and a transconductance of 370mSImm has been measured for D-mode pHEMT. Due to excellent DCI RF characteristics and good uniformity of E/D pHEMTs from optimized optical gate lithography and front-side process, the D-mode Switch and E-mode digital control circuit constitute a monolithic solution to RF control circuits in WLAN and cell phone applications.
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