Gallium arsenide metal-insulator-semiconductor field effect transistors (MISFET) with low temperature GaAs insulating layers

Metal-insulator-semiconductor field effect transistors (MISFETs) using low temperature (LT) GaAs as the insulator layer were fabricated and characterized. In this study, the influence of the AlAs spacer layer on MISFET properties is explored. Structures were grown with the thickness of the AlAs layer varied from 0 to 30 nm with the remainder of the total 60 nm insulator layer composed of LT GaAs. Two control structures were also grown, a standard metal semiconductor field effect transistor (MESFET) and a MISFET with a 50 nm Al_0.80Ga_0.20As insulator layer. Transistors with 1.2×200 μm gates and 5 μm source drain spacings were fabricated using standard processing techniques. Breakdown voltages as high as 48 V were found for the LT MISFETs, compared to 5 V for the MESFET and 12 V for the Al_0.80Ga_0.20As MISFET. The detailed characterization of the breakdown, along with the effects of the various insulating layers on other FET parameters such as current, transconductance, and cutoff frequency, is described