High Electrical Efficiency GaN FETs for Innovative Radar/RF Sensors

Improving efficiency and reliability of GaN-based FETs is paramount in enabling system insertion, both of which are limited by thermal effects and self heating in the devices. One factor limiting high voltage and high efficiency operation of GaN HEMTs is leakage current between the gate and drain at high drain bias. Pure screw dislocations arising from the lattice mismatch at the SiC substrate and thread through the GaN and AlGaN epitaxial layers have been identified as a path for reverse-bias leakage currents in GaN. The availability of a low dislocation density GaN substrate would address these issues by reducing the dislocation density to 105 cm-2 or lower. The proposed Phase I SBIR effort will work to identify key factors in improving the efficiency, of GaN-based FET devices for application in radar systems. This program will investigate the impact of defects in and thermal conductivity of device structures on SiC and bulk GaN substrates. Thermal models of GaN-based FETs on GaN substrates with comparisons to SiC substrate-based devices will be used along with thermal imaging measurements of FET structures to identify critical factors in improving the efficiency and reliability of GaN-based FETs for radar and RF sensors.