Mechanism of Current-Collapse-Free Operation in E-Mode GaN Gate Injection Transistors Employed for Efficient Power Conversion

Due to the superior characteristics of GaN to Si, they can be utilized to drastically increase the efficiency and minimize the size of power converter system. However, there has been a critical issue of the so-called current collapse where ON-state resistance is increased once GaN transistor is exposed to high voltage. From the temperature dependence of the switching characteristics of an enhancement-mode GaN transistor, we found that deep ``hole traps'' play an important role in the current collapse. Based on this finding, we proposed a new device structure where hole emission in the OFF state is compensated by the holes injected from a drain-side pGaN. It was found that the proposed device is free from current collapse up to 800V. In this paper, we proposed the mechanism for the suppression of the current collapse in the proposed GaN transistor.