Performance dependence of InGaP/InGaAs/GaAs pHEMTs on gate metallization

The performance of InGaP-based pHEMTs as a function of gate metallization is examined for Mo/Au, Ti/Au, and Pt/Au gates. DC and microwave performance of pHEMT's with 0.7-μm gate lengths is evaluated. Transconductance, threshold voltage, f
_T
, and f
_max
are found to depend strongly on gate metallization. High-speed performance is achieved, with f
_T
of 41.3 GHz and f
_max
of 101 GHz using Mo/Au gates. The difference in performance between devices with different gate metallizations is postulated to be due to a combination of the difference in Schottky barrier heights and different gate-to-channel spacings due to penetration of the gate metal into the InGaP barrier layer.