Application of superlattice gate and modulation-doped buffer for GaAs power MESFET grown by MBE

A new power GaAs MESFET (SGMBT), using the undoped superlattice gate and modulation-doped (MD) buffer, has been fabricated successfully by MBE. A much higher gate-drain breakdown voltage (30 V) and lower gate reverse leakage current have been obtained due to the existence of the undoped AlGaAs/GaAs superlattice gate insulator. The use of MD buffer structure introduces a high output resistance and low trap concentration at AlGaAs/GaAs interface. The degradation region at channel-buffer interface is estimated to be smaller than 40 Å. Thus the sharpness and smoothness between active channel and buffer is truly improved by the insertion of MD structure. The maximum output saturation current and output power of SGMBT are 300 mA/mm and 0.67 W/mm, respectively. By optimizing the device geometry and gate dimension, the output performance of SGMBT can be improved further.