Selective reactive ion etching for short-gate-length GaAs/AlGaAs/InGaAs pseudomorphic modulation-doped field-effect transistors

Abstract

Selective reactive ion etching of GaAs on AlGaAs in SiCl4/SiF4 plasma is reported. A selectivity ratio of 350:1 has been obtained at low power. A small decrease in the saturation current of gateless MODFET structures has been observed after etching the GaAs cap layer and has been ascribed to be due to low-power ion damage of the AlGaAs layer. This process was applied to the fabrication of 0.2 μm T-gate pseudomorphic MODFET’s. The dc and microwave performance of reactive-ion-etched devices and wet-etched devices were identical. However, for these short-gate-length devices a threshold voltage standard deviation of 30 mV was obtained for the reactive-ion-etched devices as compared to 230 mV for the wet-etched devices.