High Frequency Performance of AlGaN/GaN HEMTs Fabricated on SiC Substrates

Abstract

Power transistors based on gallium nitride (GaN) enable power electronic switches to operate at much higher switching frequencies compared to those based on silicon (Si). In this work, using TCAD simulations, we show that GaN-based high electron mobility transistors (HEMTs) can be optimized to have effectively reduced undesirable parasitic capacitances to greatly improve both the high transconductance and current gain cutoff frequency simultaneously. We report a new generation of high performance AlGaN/GaN HEMTs grown on high resistivity SiC substrates. We map out to evaluate small signal and large signal device performances against technological parameters such as the gate length, field plate length and the source-drain contact separation. The device with a gate length of $\mathbf{0.25}\mu\mathbf{m}$ and field plate length of $\mathbf{0.3}\mu\mathbf{m}$ exhibits a maximum dc drain current density of 3.66 A/mm at $\mathbf{V}_{\mathbf{GS}}=3\mathbf{V}$ with an extrinsic transconductance of 233.6 mS/mm and an extrinsic current gain cut-off frequency $(\mathbf{f}_{\mathbf{t}})$ of 78.9 GHz.