HIGH-POWER-DENSITY GAAS MISFETS WITH A LOW-TEMPERATURE-GROWN EPITAXIAL LAYER AS THE INSULATOR

A GaAs layer grown by molecular beam epitaxy (MBE) at 200-degrees-C was used as the gate insulator for GaAs metal-insulator-semiconductor field-effect transistors (MISFET's). The gate reverse breakdown and forward turn-on voltages were improved substantially by using the high-resistivity GaAs layer between the gate metal and the conducting channel. A reverse bias of 42 V or a forward bias of 9.3 V is needed to reach a gate current of 1 mA/mm of gate width. A MISFET having a gate of 1.5 x 600-mu-m delivered an output power of 940 mW (1.57-W/mm power density) with 4.4-dB gain and 27.3% power-added efficiency at 1.1 GHz. This is the highest power density reported for GaAs-based FET's.