Performance Degradation of GaN HEMTs Under Accelerated Power Cycling Tests

Abstract

In this paper, performance degradations of enhancement mode (E-mode) gallium nitride (GaN) high-electronmobility-transistors (HEMTs) under accelerated power cycling tests are presented. For this purpose, a DC power cycling setup is designed to accelerate the aging process in a realistic manner. In order to evaluate the aging-related parameter shifts and corresponding precursors, electrical parameters are periodically monitored through a high-end curve tracer. Both the cascode device and p-GaN gate GaN devices are evaluated during these tests. In the experimental results, it is observed that the onstate resistance gradually increases in both devices. Meanwhile, the threshold voltage of the p-GaN gate GaN device gradually increases over the aging cycles and a remarkable variation in the transfer characteristics is observed. At the end of the tests, failure analyses are conducted on both devices. The cascode GaN devices show both short and open circuit failure modes, and a weak point in the drain-side bond wires is detected. For the p-GaN gate GaN device, the electrical parameter shifts indicate a possible gate degradation after the device is aged. Index Terms-Aging precursor, failure analysis, failure mode, failure model, GaN device, power cycling. I. IntroductIon G ALLIUM nitride (GaN) devices are one of the most promising power devices in high frequency, high efficiency and high power density power conversions [1], [2]. Compared to Si and SiC counterparts, GaN high-electron-mobility transistors (HEMTs) exhibit a better figure of merit. The GaN HEMTs can be categorized into normally-on and normally-off devices [3]. Normally-on GaN device is less desirable in power converters due to its reliability concerns. For normally-off GaN devices, there are several methods to implement, including recessed Schottky gate, p-GaN gate, plasma treatment under the gate and cascode structure [4]. Among them, the cascode GaN and p-GaN gate GaN are mainly applied in commercially available GaN devices as shown in Fig. 1. Both these types of GaN devices show different characteristics from the conventional Si devices. For cascode GaN devices, there are two primary heat sources, i.e., the GaN HEMT

Characterizing Threshold Voltage Shifts and Recovery in Schottky Gate and Ohmic Gate GaN HEMTs

“…Commercially available GaN HEMTs have been the subject of different studies including electrothermal characterization [5][6][7]and reliability studies (summarized in [8]), with a JEDEC committee (JC-70) focused on the development of standards for GaN power devices [9,10]. The reliability studies include power cycling [11][12][13], dynamic ON-state resistance [14][15][16] and threshold voltage (VTH) instability [17][18][19][20][21][22][23], which is the focus of the investigations presented in this paper.…”

Stability, Reliability, and Robustness of GaN Power Devices: A Review

“…Power cycling experiments are primarily used to stress the packaging of a commercial device and the interface between the device and package. The stress is created through the repeated, (self) heating of the device with ON-state current causing strain in the mechanical layers due to the differences in the coefficient of thermal expansion mismatch [49]- [51].…”

“…The p-gate GaN HEMTs have been reported to show VTH and R DS,ON increase in power cycling [49], [51]. Depending on the magnitude of the temperature swing, I DSS has also shown to increase as well [49], [52].…”

A Review of Megahertz Current Sensors for Megahertz Power Converters

“…3(b), which conventionally is performed for evaluating the reliability of the DUT under different temperature stresses [59]- [63]. But unlike DPT, the current measured here is for decisive feedback control and/or failure detection [64]- [65].…”