Study of current collapse by quiescent-bias-stresses in rf-plasma assisted MBE grown AlGaN/GaN high-electron-mobility transistors

Studies on the influence of quiescent-gate (Vgs0) and quiescent-drain (Vds0) bias stresses in rf-plasma MBE grown AlGaN/GaN high-electron-mobility transistors (HEMTs) were performed. The increase of drain current (ID) collapse by quiescent-bias-stress in AlGaN/GaN HEMTs were observed using pulsed (pulse width = 200 ns; pulse period = 1 ms) IDS–VDS characteristics. The Si3N4 passivation suppressed about 80% ID collapse in quiescent-bias-point stressed HEMTs. The remaining 20% ID collapse were not suppressed which may be coming from buffer-related traps. However, more than 10% of ID collapse suppression was observed on un-stressed or fresh-HEMTs. Similarly, improved cut-off frequency (fT), maximum oscillation frequency (fmax) and device output power (Pout) values were also observed on the un-stressed HEMTs. The Si3N4 passivation completely suppressed the ID collapse in un-stressed or fresh-HEMTs which leads to 70% improvement in fT and 60% improvement in the device Pout. The Si3N4 passivation did not completely suppress ID collapse in the quiescent-bias stressed-HEMTs. This may be due to the generation of additional surface-related traps in the HEMTs by quiescent-bias-stresses.