Role of Excited Surface States in Increasing IOFF in AlGaN/GaN HEMT: Effect of White Light Illumination and Elevated Temperature

Abstract

This work investigates the influence of excited surface states on the off current (IOFF) in AlGaN/GaN high-electron-mobility transistors (HEMTs). A detailed mechanism is presented, showing that white light illumination and elevated temperature increase the surface potential on the GaN cap, which lowers the potential barrier beneath the gate. This barrier reduction enhances electron leakage through the GaN buffer, leading to higher IOFF. Furthermore, a left shift in threshold voltage with increasing light intensity is observed, demonstrating threshold voltage instability induced by surface states under optical and thermal excitation.