Analysis of Gate-Metal Resistance in CMOS-Compatible RF GaN HEMTs

To enable CMOS-compatible GaN HEMTs for the next generation of communication systems (5G and beyond), a low gate resistance is of great importance since it directly affects the RF power gain and fMAX of the transistor. In this article, the impact of various gate-metal stacks on the gate resistance and RF performance of the devices is studied. The optimized Ti-free gate-metal process leads to fMAX enhancement up to 50% for devices scaled down to 0.32-μm gate lengths. The gate resistance for the T-shaped gate is modeled from the S-parameters and validated on various gate field plate geometries. The tradeoff between the gate resistance and the parasitic capacitance in GaN HEMTs is highlighted in this case.