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 ( ΔV
_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 ΔV
_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 ΔV
_T
<; 0 V ( E
_A
≈ 0.5 eV) under moderate stress is attributed to the emission of electrons from oxide and interface traps. Instead, ΔV
_T
> 0 V ( E
_A
≈ 0.9 eV) under high stress is attributed to the increased negatively ionized acceptor trap density in the buffer associated with carbon doping.