GaAs-based metal-oxide-semiconductor field-effect transistor with aluminum oxide gate insulator prepared in situ by MOCVD

Abstract

Preparation and properties of GaAs-based metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) are described. Aluminum oxide as a passivation and gate insulator was formed by room temperature oxidation of a thin Al layer deposited in situ on top of the InGaAs-channel/GaAs-substrate layer structure by metal-organic CVD (MOCVD). The devices yielded a maximum drain current of 480 mA mm−1 and a peak extrinsic transconductance of 147 mS mm−1. The devices exhibited negligible capacitance dispersion with frequency, which indicates low density of trap states in the structures prepared. From the microwave measurements, extracted current gain and unilateral power gain cutoff frequencies were 19 and 48 GHz, respectively, on devices with 1.5 µm gate length. Device modeling based on measured small signal S-parameters shows that the transconductance is predominantly responsible for an enhancement of the MOSHFET microwave performance.