| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系所 === 97 === The RF and digital performance of InGaP/In0.22Ga0.78As pseudomorphic high electron mobility transistors (PHEMTs) with different doping profiles are investigated. In order to improve the device linearity for RF applications, the uniformly-doped and channel-doped structures are designed and the devices are compared. The uniformly- doped device shows higher IP3 of 22.19 dBm, and the channel-doped device shows higherΔ(IP3-P1dB) of 14.23 dB and higher IP3 to DC power consumption ratio (IP3/PDC) of 4.97 compared to other devices. Figures of merits of these devices for digital applications are also evaluated. SS and ION/IOFF ratio parameters can be improved by uniformly-doping in the Schottky layer and DIBL parameter can be reinforced by extra doping in the channel layer.
For digital applications, the InGaAs channel with high indium concentration is required for better performance and higher transconductance. In addition, atomic layer deposition (ALD) Al2O3 is introduced to act as the gate insulator to reduce gate leakage current and increase breakdown voltage. Thus, the InAlAs/In0.7Ga0.3As metal-oxide-semiconductor metamorphic HEMTs (MOS-MHEMTs) and InAlAs/InAs MOS-HEMTs were fabricated and the insulating properties were improved. Moreover, the InAlAs/InAs MOS-HEMTs employing air-bridge structure with different gate widths exhibit similar threshold voltage, leading to the possibility for digital utilization of different fan-out level.
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