High Voltage and Low Leakage GaN-on-SiC MISHEMTs on a “Buffer-Free” Heterostructure

The performance of a novel ‘buffer-free’ AlGaN/GaN-on-SiC MISHEMTs for power switching applications is demonstrated in this letter. High voltage operation with exceptionally low gate and drain leakage currents is shown. A specific on-resistance of 3.61 m $\boldsymbol {\Omega } \cdot $ cm² and an abrupt breakdown voltage of 1622 V at a drain current of 22 nA/mm is achieved. Using two-terminal breakdown measurements, nitrogen-implanted GaN display breakdown fields of 0.96 MV/cm. The semi-insulating SiC substrate is capable of suppressing vertical leakage currents, ensuring that off-state operation is limited by lateral breakdown. The impact of electron trapping effects on dynamic on-resistance is small up to a drain quiescent voltage of at least 240 V. Drain current transient characteristics display a 14% increase in dynamic on-resistance with respect to quiescent drain bias, and a negligible change in resistance up to 100 ms. These types of ‘buffer-free’ heterostructures are of interest for power electronic applications above 1000 V and with potential for co-integration of power and RF-electronics.

I. Introduction

The interest in wide-bandgap Gallium Nitride (GaN) and its compounds (AlGaN, InGaN, etc.) has increased substantially over the past decades owing to their high critical electric fields in combination with excellent electron transport properties [1]. These properties make III-nitride materials suitable for both high-power and high-frequency applications. GaN-based high electron mobility transistors (HEMTs) provide additional advantages, such as small parasitic capacitances and reverse recovery charge, which results in low switching losses in power applications [2].