Vertical heterojunction field-effect transistors utilizing re-grown AlGaN/GaN two-dimensional electron gas channels on GaN substrates

Vertical heterojunction field-effect transistors (VHFETs) utilizing 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 m Omega cm(2) at a threshold voltage (V-th) 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 Al concentration. A normally-off operation was achieved with a 10-nm-thick Al0.2Ga0.8N layer. The possibility that VHFET with smaller current collapse phenomena than planar HEMT was revealed. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim