Analysis of the Degradation of Depletion-Mode GaN High-Electron-Mobility Transistors Under Reverse Pulse Electrical Stress Using the Voltage-Transient Method

The effects of reverse pulse electrical stress on the electrical and trapping properties of Depletion-Mode (D-Mode) GaN high-electron-mobility transistors (HEMTs) are investigated in this paper. The results of HEMT testing show that the device's electrical characteristics in the OFF-state are degraded after reverse pulse electrical stress cycling, along with the gate-to-source reverse current and drain-to-source leakage current characteristics. In particular, three traps in the device are identified using the voltage-transient method, and the trapping effects in the HEMT are investigated after 70000 pulses of gate reverse electrical stress are applied. The sources of the traps identified in the study include interface traps near the surface of AlGaN or at the SiN interface (DP1), intrinsic defects such as N antisites in the GaN buffer (DP2), and traps in the gate-drain access region (DP3). Comparison with the transient voltage characteristics of the original device shows that the absolute amplitudes of the traps in the device increase after application of the electrical stress, thus indicating an increment in the trap density. It was found that DP1 remained unchanged before and after stress application, which may be the result of an inadequate surface passivation process. With regard to the other two traps, the electrical stress increases the trap density of DP2 and causes the emergence of DP3 as one new trap. These results may be useful in the design and application of AlGaN/GaN HEMTs. These results may be useful in the design and application of AlGaN/GaN HEMTs.