Novel Vertical Heterojunction Field-Effect Transistors with Re-grown AlGaN/GaN Two-Dimensional Electron Gas Channels on GaN Substrates

Abstract

Novel vertical heterojunction field-effect transistors (VHFETs) with re-grown AlGaN/GaN two-dimensional electron gas (2DEG) channels on free-standing GaN substrates have been developed. The VHFETs exhibited a specific on-resistance (RonA) of 7.6 mΩ cm2 at a threshold voltage (VTH) of -1.1 V and a breakdown voltage (VB) of 672 V. The breakdown voltage and the figure of merit (VB2/RonA) are the highest among those of the GaN-based vertical transistors ever reported. It was demonstrated that the threshold voltage can be controlled by the thickness of AlGaN layers and a normally-off operation was achieved with a 10-nm-thick Al0.2Ga0.8N layer.