E-mode GaN HEMT short circuit robustness and degradation

The emerging 650 V large current rating, Enhancement-mode (E-mode) Gallium Nitride High-Electron-Mobility Transistor (GaN HEMT) is a promising device for low to medium power, high power density converters (e.g., motor drives, battery chargers), which require high robustness levels. Thus, a comprehensive study of the short circuit behavior of high power E-mode GaN HEMT is the subject of this paper. The study begins with an introduction of the short circuit test platform and method. Subsequently, single pulse, 10 μs short circuit tests are performed to extract the short circuit behavior of high power GaN HEMT, from 50 V to 400 V, at room temperature. Significant drain current reduction (> 75%) caused self-protection phenomenon and quick failure has been observed at different dc-bus voltage. Then, repetitive short circuit tests followed to reveal the degradation trend of the E-mode GaN HEMT after short circuit stress. What results is an obvious device output current capability reduction and gate-to-source threshold voltage shifting. Since the short circuit performance of high power E-mode GaN HEMT has never been reported, this paper shows the critical need to further improve GaN converter robustness from both a device and circuit standpoint.

I. Introduction

The GaN HEMT has become one of the most attractive power transistors in recent years due to its superior electrical performance. Many GaN-based prototypes have demonstrated both higher efficiency and power density; its applications include, but are not limited to, point of load converters, power adapters, battery chargers, PV and motor inverters [1]–[11]. Among all types of GaN HEMTs, the E-mode GaN HEMT is especially preferred by power electronics designers, since it has the normally off behavior and the widest available power range in the market. However, in many applications, E-mode GaN HEMTs can suffer from extreme operation conditions, resulting in a short-circuit fault. Thus, it is important to understand the short circuit behavior and capability of E-mode GaN HEMTs, especially for 600/650V class, large current rating chips. This information will not only benefit device manufacturers but will also help gate drive circuit and converters designers.