| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 93 === In this thesis, using Ga2O3(Gd2O3) as a gate dielectric, we have designed two different structures of depletion-mode(D-mode) GaAs MOSFET's, with GaAs and InGaAs/GaAs as channels. By changing the thickness of oxide, but retaining the same doping concentration, the effects of different channel design on device performance were investigated. Future work is being planned to to improve it.
We have sucessfully fabricated D-mode Ga2O3(Gd2O3)/GaAs and Ga2O3(Gd2O3)/ In0.15Ga0.85As /GaAs MOSFET's. In addition, we have found out that a great improvement on device characteristics was achieved with a final annealing.
D-mode GaAs MOSFET’s with Ga2O3(Gd2O3) as a gate dielectric, a dimension of 1.6 um x 100 um, have shown high accumulation currents of 335 mA/mm at a gate bias of VG = 4V, transconductance of over 130 mS/mm when Vd=3V, pinch-off voltage of -3V, and the device breakdown voltage of over 15V. Also, gate leakage current versus biasing voltage of the fabricated device shows a symmetrical behavior in 10-6A range after forming gas annealing for 3 hours.
Ga2O3(Gd2O3)/ In0.15Ga0.85As /GaAs MOSFET has drain saturated current of 115mA/mm, and a maxmimum transconductance of 171 mS/mm was achieved by inserting an In0.15Ga0.85As channel layer between oxide and the GaAs channel with the same device dimension.
In this work, we report the first achievement of a strong accumulation current at Vg larger than 3 V in a D-mode GaAs MOSFET and both devices have shown no hysteresis in drain currents.
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