650 V 3.1 mΩcm2 GaN-based monolithic bidirectional switch using normally-off gate injection transistor

We report a normally-off GaN-based monolithic bidirectional switch for the first time. The switch consists of a double-gate AlGaN/GaN gate injection transistor (GIT) which serves normally-off operation with high drain current utilizing the hole injection from the p-type gate. The fabricated bidirectional switch exhibits high breakdown voltage of 650 V for both polarities and low on-state resistance (R_on ^.A) of 3.1 mΩcm² . The GaN-based bidirectional switch can be applied to AC-AC matrix converters with high efficiency.

Introduction

AC-AC matrix converters shown in Fig. 1 are intensively investigated, driven by the strong motivation to replace conventional DC-linked-type AC-AC converters used in AC motor-drive systems [1], [2]. The matrix converter using fully controlled four-quadrant bidirectional switches enables extremely high AC-AC conversion efficiency together with reduced system volume by eliminating large DC-link capacitors, as is summarized in Table 1 [1]. So far, a common configuration for the bidirectional switch with reverse blocking capability has been using two Insulated Gate Bipolar Transistors (IGBTs) connected in anti-parallel, where a diode is connected in series with each IGBT. However, the reduction of the conduction loss is limited because of the on-state voltage offsets caused by the series diode and by the IGBT.