REFRACTORY WNX W SELF-ALIGNED GATE GAAS POWER METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTOR FOR 1.9-GHZ DIGITAL MOBILE COMMUNICATION-SYSTEM OPERATING WITH A SINGLE LOW-VOLTAGE SUPPLY/

We have developed a refractory WNx/W self-aligned gate GaAs power meta l-semiconductor field-effect transistor (MESFET) for use in L-band dig ital mobile communication systems. This power MESFET operates with hig h efficiency and low distortion at a gate bias of 0 V and a low drain bias of 2.7 V, because of its small drain knee voltage, high transcond uctance and sufficient breakdown voltage. This power MESFET is quite p romising for a highly efficient linear power amplifier IC operating wi th a single low-voltage supply. Good output characteristics of the pow er MESFET with 1 mm gate width were attained for pi/4-shifted quadratu re phase shift keying (QPSK) modulated input signals in the 1.9-GHz ba nd, such as an output power of 18.4 dBm, a power gain of 19.0 dB and a high power-added efficiency of 26.4% when a sufficiently low adjacent channel leakage power of -58 dBc was obtained.