Enhancing Breakdown Voltage and Switching Performance in AlGaN/GaN HEMTs via GaN Cap and Field Plate Co-Design

This work presents a detailed Sentaurus TCAD investigative study on a co-design technique integrating a GaN cap layer (Gcap) and a gate field plate (FP) in AlGaN/GaN high electron mobility transistors (HEMTs). Seven device structures, ranging from a baseline (without Gcap–FP) to various Gcap–FP combinations, are analyzed to optimize performance for RF and high-power applications. The optimized device (Gcap3/FP3) demonstrates a maximum Ion/Ioff ratio of 3.97 × 108, a breakdown voltage (VBR) of 935 V, and a Johnson’s figure of merit (JFoM) of 532.95 MHz·V, indicating excellent high-voltage and low-leakage characteristics. However, this configuration exhibits trade-offs in transconductance. The observed RF metrics namely, a cutoff frequency (ft) of 0.57 GHz, and a maximum frequency (fmax) of 0.66 GHz, validates the effectiveness of Gcap–FP co-design in enhancing performance of AlGaN/GaN HEMTs in next-generation RF and power switching applications.