Suppression of Current Collapse in Enhancement-Mode AlGaN/GaN High Electron Mobility Transistors

The phenomenon of current collapse was investigated on p-GaN/AlGaN/GaN enhancement-mode high electron mobility transistors. Contrary to our original thought of carrier depletion on the p-GaN/AlGaN/GaN layers so that less carrier traps, current collapse was observed from such a device without surface passivation. The results were compared with the device passivated with SiO2 dielectric, which showed much less severe current collapse within the gate bias of -15 V. To understand the mechanism of dielectric passivation, the capacitance-voltage measurement was performed. Our results show that the donor-like dislocations in the SiO2/GaN interface help to deplete carriers on the device surface and within the p-GaN, thus maintaining channel carriers and mitigating current collapse.