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

In this brief, we investigate the bidirectional threshold voltage drift (VT) 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 (VGS,STR); 2) stress times (tSTR); and 3) temperatures (T). Both negative and positive VT (thermally activated with different activation energies, EA) were observed depending on the magnitude of VGS,STR. In accordance with the literature, observed VT < 0 V (EA ≈ 0.5 eV) under moderate stress is attributed to the emission of electrons from oxide and interface traps. Instead, VT > 0 V (EA ≈ 0.9 eV) under high stress is attributed to the increased negatively ionized acceptor trap density in the buffer associated with carbon doping.