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.

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 mΩcm2 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 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 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

With the rapid depletion of communication-frequency resources, mainly due to the explosive spread of information communication devices for the internet of things, GaN-based high-frequency high-power transistors (GaN-HEMTs) have attracted considerable interest as one of the key devices that can operate in the high-frequency millimeter-wave band. However, GaN-HEMT operation is destabilized by current collapse phenomena arising from surface electron trapping (SET), which has not been fully understood thus far. Here, we conduct quantitative mechanistic studies on SET in GaN-HEMTs by applying element- and site-specific photoelectron nanospectroscopy to a GaN-HEMT device under operation. Our study reveals that SET is induced by a large local electric field. Furthermore, surface passivation using a SiN thin film is demonstrated to play a dual role: electric-field weakening and giving rise to chemical interactions that suppress SET. Our findings can contribute to the realization of high-capacity wireless communication systems based on GaN-HEMTs.

No abstract

No abstract