10 W/mm and High PAE Field-plated AlGaN/GaN HEMTs at Ka-band with n+GaN Source Contact Ledge

摘要

Continuous progress in wide bandgap GaN/AlGaN-based HEMTs since 1993 [1] has pushed its frequency performance beyond X-band into millimeter-wave range. In particular, there has been growing interest of wide bandgap semiconductors for K-, Ka-, Q, and W-band [2] applications. While the early performances in these bands was obtained from GaN/AlGaN HEMTs fabricated with T-gates, recently demonstrated field-plated (FP) AlGaN/GaN-based HEMTs have shown dramatically improved RF power performance, where the FP devices were fabricated with reduced gate capacitance. Field-plated GaN/AlGaN HEMTs with deep-submicron gatelengths offered excellent large-signal performance with power density of 5.7 W/mm and PAE of 45% at 30 GHz [3]. At 40 GHz, the CW power density of 10.5 W/mm was measured with PAE of 34% [4]. The FP devices appear to enable reliable long-term operation. While the large-signal performance of AlGaN/GaN HEMTs is improved in the FP devices, their PAE, power density and linearity can be further improved if their high 2DEG sheet resistance, non-linearity in transconducance, access resistance and saturation velocity are addressed properly in device design.