Gate Reliability of p-GaN Gate AlGaN/GaN High Electron Mobility Transistors

The gate reliability of p-GaN gate AlGaN/GaN high electron mobility transistors with a ring-gate structure is investigated by step-stress experiments under a gate bias, combined with electroluminescence imaging and pulsed measurements. For gate stress (V
_Gstress
) from 0 to 13 V, the drain current is found to be stable and decreases at 13 V at OFF-state and increases at ON-state. For V
_Gstress
from 13 to 31 V, the drain current increases at OFF-state and decreases at ON-state, whereas V
_TH
is stable and increases slightly. The changes in drain current characteristic and V
_TH
values of the device after applying various V
_Gstress
are associated with the injection and trapping of holes from the p-GaN layer to the AlGaN layer, supported by the results of pulsed measurements and by the simulation of energy band diagrams. When V
_Gstress
is further increased to a high voltage of 31 V, V
_TH
becomes noisy and a strong luminescence signal occurs with a sudden reduction in the drain current, and finally, a catastrophic failure happens in the gate-channel region.