Investigation of current collapse mechanism of LPCVD Si3N4 passivated AlGaN/GaN HEMTs by fast soft-switched current-DLTS and CC-DLTFS

In this work, we investigated the current collapse mechanism of AlGaN/GaN high-electron mobility transistors (HEMTs) with LPCVD Si3N4 passivation. With newly developed fast soft-switched current-DLTS techniques, we achieved current acquisition within 100 ns after each stress pulse and with high sampling rate up to 5 MSa/s. A single trap level (∼66 meV) and capture cross section On (−1.05×10−20 cm−2) has been found within the AlGaN/GaN HEMTs surface. Moreover, this trap level is confirmed by low-temperature Constant-Capacitance Deep-Level Transient Fourier Spectroscopy (CC-DLTFS) measurement on GaN MIS-diode structure. Although this trap level is quite shallow, it can still lead to current collapse in LPCVD-SiNx-passivated AlGaN/GaN HEMTs due to the small On.