Mechanisms Underlying the Bidirectional V T Shift After Negative-Bias Temperature Instability Stress in Carbon-Doped Fully Recessed AlGaN/GaN MIS-HEMTs

Abstract

In this brief, we investigate the bidirectional threshold voltage drift ( $\Delta {V}_{T}$ ) following negative-bias temperature instability (NBTI) stress in carbon-doped fully recessed AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). Several stress conditions were applied at different: 1) gate biases ( ${V}_{GS,STR}$ ); 2) stress times ( ${t}_{STR}$ ); and 3) temperatures ( ${T}$ ). Both negative and positive $\Delta {V}_{T}$ (thermally activated with different activation energies, ${E}_{A}$ ) were observed depending on the magnitude of ${V}_{GS,STR}$ . In accordance with the literature, observed $\Delta {V}_{T} V ( ${E}_{A}~\approx ~0.5$ eV) under moderate stress is attributed to the emission of electrons from oxide and interface traps. Instead, $\Delta {V}_{T} >0$ V ( ${E}_{A}~\approx ~0.9$ eV) under high stress is attributed to the increased negatively ionized acceptor trap density in the buffer associated with carbon doping.