Gate-structure optimization for high frequency power AlGaN/GaN HEMTs

Abstract

The influence of gate-head and gate-source-spacing on the performance of AlGaN/GaN HEMTs was studied. Suggestions are then made to improve the performance of high frequency power AlGaN/GaN HEMTs by optimizing the gate-structure. Reducing the field-plate length can effectively enhance gain, current gain cutoff frequency and maximum frequency of oscillation. By reducing the field-plate length, devices with 0.35 μm gate length have exhibited a current gain cutoff frequency of 30 GHz and a maximum frequency of oscillation of 80 GHz. The maximum frequency of oscillation can be further optimized either by increasing the gate–metal thickness, or by using a τ-shape gate (the gate where the gate-head tends to the source side). Reducing the gate–source spacing can enhance the maximum drain-current and breakdown voltage, which is beneficial in enhancing the maximum output power of AlGaN/GaN HEMTs.