N-Polar GaN-on-Sapphire Deep Recess HEMTs With High W-Band Power Density

Abstract

This work presents recent progress in the W-band (94 GHz) power performance of N-polar GaN deep recess HEMTs grown on sapphire substrates. While SiC has been the substrate of choice to achieve the highest level of performance, sapphire substrates are a lower cost alternative. In this work we show that N-polar GaN deep recess HEMTs grown on sapphire match the power performance of a device on SiC up to 14 V with 5.1 W/mm of output power density. At 16 V the device on sapphire starts to suffer from thermal effects but still demonstrated 5.5 W/mm with an associated 20.6% power-added efficiency. This work also examines the impact of encapsulating the device in a low dielectric constant film often used for the implementation of a RF wiring environment.