leakage current

algan gan

gan hemts

drain current

threshold voltage

IEEE electron device letters

In this letter, we investigate by means of experimental results and TCAD simulations the threshold voltage instability due to OFF-state drain stress in p-GaN gate AlGaN/GaN-on-Si HEMTs. When the drain of the p-GaN HEMT is biased in the OFF-state the threshold voltage (   ${V}_{\text {th}}$   ) shows a linear increase up to ~40%. This increase saturates at drain bias voltages above 50 V. The positive    ${V}_{\text {th}}$    shift is attributed to the ionization of acceptor traps in the AlGaN region below the p-GaN gate with the source of these trapping sites suggested to be the p-GaN gate out-diffused Mg dopant atoms. The ionization of the Mg acceptors due to high electric field during OFF-state bias and the removal of the generated holes from the AlGaN region through the gate contact creates the charge conditions for a positive    ${V}_{\text {th}}$    shift. The sharp decrease in the gate drain capacitance (   ${C}_{\text {gd}}$   ) for    ${V}_{D}   V, the simulated gate edge electric field reaching its peak for a drain voltage bias    ${V}_{D} \sim {50}$    V and the positive threshold voltage shift observed for negative gate stress further validate the proposed model.

Understanding the Threshold Voltage Instability During OFF-State Stress in p-GaN HEMTs