Fabrication and characterization of AIGaN/GaN HEMTs
The processing procedure for the formation of ohmic contact using Ti/Al/Pd/Au, and Schottky contact using Pd/Au on AlGaN/GaN HEMT has been developed. A specific contact resistance of 1.08 x 10-7 W cm2 was achieved and an Schottky barrier height of 1.12eV was reached. Large dimension AlGaN/GaN HEMT devices with two different epilayer designs have been fabricated. A maximum drain current of 800mA/mm and a peak transconductance of 165mS/mm was achieved with the first HEMT design compared to 500mA/mm and 106mS/mm for the second HEMT design. Long-term heat treatment on the HEMT was found to degrade the surface morphology of the Pd/Au gate but improved the ohmic behavior of the HEMT. A set of photomask for fabrication of high power, high frequency HEMTs has been designed. A new epilayer design was developed to achieve a multi-channel AlGaN/GaN HEMT using piezoelectric polarization effect. Simulation showed better dc performances than HEMTs with conventional design.
GaN, HEMT, Ohmic, Schottky, rf photomask, Simulation
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