A study on Al₂O₃ passivation in GaN MOS-HEMT by pulsed stress

This paper studies systematically the drain current collapse in AlGaN/GaN metal--oxide--semiconductor high electron mobility transistors (MOS-HEMTs) by applying pulsed stress to the device. Low-temperature layer of A1₂O₃ ultrathin film used as both gate dielectric and surface passivation layer was deposited by atomic layer deposition (ALD). For HEMT, gate turn-on pulses induced large current collapse. However, for MOS-HEMT, no significant current collapse was found in the gate turn-on pulsing mode with different pulse widths, indicating the good passivation effect of ALD A1₂O₃. A small increase in I_dd in the drain pulsing mode is due to the relieving of self-heating effect. The comparison of synchronously dynamic pulsed I_dd-V_ds characteristics of HEMT and MOS-HEMT further demonstrated the good passivation effect of ALD A1₂O₃.