Kilovolt AlGaN/GaN HEMTs as Switching Devices

TLDR

SiC devices have been the focus for high‑voltage, high‑temperature switching due to low on‑resistance, but GaN HEMTs offer a competitive alternative with a wider bandgap, higher electric strength, higher saturated velocity, and the benefit of SiC substrate thermal conductivity. The paper projects and compares the performance of GaN HEMTs with SiC devices. The fabricated AlGaN/GaN HEMT achieved a 1050 V breakdown, 3.4 mΩ cm² on‑resistance, 4 kA cm⁻² current density, and a figure of merit V²BR/Ron of 3.24 × 10⁸ V² Ω⁻¹ cm⁻², demonstrating superior performance over SiC devices.

Abstract

SiC devices have been the focus for several years as potential high voltage switches working at high temperature with very low on-resistance. Another competitive candidate for this application is the GaN HEMT (high electron mobility transistor). GaN has slightly wider bandgap, higher electric strength, and higher saturated velocity than SiC. The most prominent is that by utilizing the AlGaN/GaN heterojunction, the GaN HEMT has much higher charge density (up to 2 × 1013 cm—2) and mobility (up to 2200 cm2/Vs) in the channel compared to SiC MOSFET or JFET, yielding much lower on-resistance than SiC devices. GaN grown on SiC substrate also takes the advantage of high thermal conductivity of SiC. A GaN HEMT with a breakdown voltage of 1050 V was fabricated with a specific on-resistance of 3.4 mΩ cm2 and current density of 4 kA cm—2. State-of-art power device figure of merit of V2BR/Ron = 3.24 × 108 [V2 Ω—1cm—2] was achieved on this device. Projected performance of GaN HEMTs is also discussed and compared with SiC devices in this paper.