Investigation of Surface- and Buffer-Induced Current Collapse in GaN High-Electron Mobility Transistors Using a Soft Switched Pulsed \(I-V\) Measurement

In this letter, we investigated the behaviors of surface- and buffer-induced current collapse in AlGaN/GaN high-electron mobility transistors (HEMTs) using a soft-switched pulsed\(I-V\)measurement with different quiescent bias points. It is found that the surface- and buffer-related current collapse have different relationship with the gate and drain biases (V\(_{ { {\!GS0,}}}\)V\(_{ { {\!DS0}}}\)) during quiescent bias stress. The surface-induced current collapse in devices without passivation monotonically increases with the negativeV\(_{ { {\!GS0}}}\), suggesting that an electron injection to the surface from gate leakage is the dominant mechanism and the Si3N4passivation could effectively eliminate such current collapse. The buffer-induced current collapse in devices with intentionally carbon-doped buffer layer exhibits a different relationship withV\(_{ { {\!GS0}}}\)after surface passivation. The buffer-related current collapse shows a bell-shaped behavior withV\(_{ { {\!GS0}}}\), suggesting that a hot electron trapping in the buffer is the dominant mechanism. The soft-switched pulsed\(I-V\)measurement provides an effective method to distinguish between the surface- and buffer-related current collapse in group III-nitride HEMTs.