Improved X-Band Performance and Reliability of a GaN HEMT With Sunken Source Connected Field Plate Design

The world class performance and reliability of a high-power density AlGaN/GaN high electron mobility transistor (HEMT) with an innovative sunken source connected field plate (SCFP) is reported. The optimized HEMT structure implements a novel sunken SCFP design that has significant advantages over the conventional field plated GaN HEMT. The new design reduced parasitic capacitances (C_gs and C_gd) whilst suppressing the peak electric fields in the drift region to improve breakdown voltage and reliability. This sunken SCFP demonstrates the improved RF performance and reliability with respect to leading GaN HEMT devices for x-band applications. The fabricated device produces 10 GHz performance with saturated output power >10 W/mm, linear gain >18 dB and PAE > 60% @ 50 V. The improved gain is a direct result of the reduction in Cgs and Cgd, by 15% and 60%, respectively. The increased power is achieved from lower trapping and increased drain voltage rating of 25%. Accelerated RF-driven reliability testing is shown to determine the expected lifetime of the device was >6E7 hours at 225°C junction temperature. This is a more than 2 orders of magnitude increase over the conventional field plate design.