Limitations for Reliable Operation at Elevated Temperatures of Al_2O_3/AlGaN/GaN Metal–Insulator– Semiconductor High-Electron-Mobility Transistors Grown by Metal-Organic Chemical Vapor Deposition on Silicon Substrate

摘要

Herein, the gate degradation mechanisms of gallium nitride (GaN)-based metal– insulator–semiconductor high-electron-mobility transistors (MISHEMTs) utilizing Al_2O_3 grown by plasma-enhanced atomic layer deposition (PEALD) are systematically investigated. By applying constant voltage stress and the time-dependent dielectric breakdown (TDDB) methodology under variation of bias and temperature, an activation energy of 1.25 eV for the time to breakdown and a 1/E model extrapolating the lifetime are found. A maximum gate operation voltage at 298 K of 4.9 V is extrapolated, which decreases to a projected voltage of 3.5 V at 598 K operation temperature, due to an accelerated defect generation. The physical origin of the TDDB of Al_2O_3 is related to the formation of a percolation path by randomly generated defects in the oxide under stress bias. This mechanism, which also requires the presence of an initial defect density in Al_2O_3, is confirmed by Monte Carlo simulations, which are in agreement with the experimental data.