Hot-electron-stress degradation in unpassivated GaN/AlGaN/GaN HEMTs on SiC

Long term on-state and off-state stress on GaN/AlGaN/GaN HEMTs on SiC substrates are presented. Hot carrier effects and their dependence on bias conditions are evaluated with electroluminescence measurements. Both hot-electron stress conditions produce drain current gate-lag dispersion and gate current decrease. However on- and off- state stresses induce degradation in different gate-to drain surface device regions, i.e. close to the drain contact for the on-state stress and close to the gate contact in the off - state stress. Furthermore a correlation between gate-leakage current and gate-lag dispersion is also observed.