Optimization of field-plate AlGaN/GaN HFETs for high-voltage and high-frequency operation

We performed physics-based 2-dimensional TCAD device simulations to optimize field-plated AlGaN/GaN heterostructure field effect transistors (HFETs) for high-power and high-frequency operation. The effects of the field plate dimensions and the passivation dielectric materials were investigated. The results showed that dimensional changes in the field plates significantly affected the breakdown and frequency performance. Silicon nitride, a widely-used passivation material for this technology, also turned out to have a benign effect on high-voltage operation whereas it had a detrimental effect on high-frequency operation. In this work, double-layered passivation with a source field plate was proposed and optimized to secure both high-voltage and high-frequency operation. The optimized devices maintained high breakdown voltage performance without compromising frequency response and without increasing fabrication complexity.