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

摘要

Studies on the influence of quiescent-gate (V_(gs0)) and quiescent-drain (V_(ds0)) bias stresses in rf-plasma MBE grown A/GaN/GaN high-electron-mobility transistors (HEMTs) were performed. The increase of drain current (I_D) collapse by quiescent-bias-stress in AlGaN/GaN HEMTs were observed using pulsed (pulse width = 200 ns; pulse period-1 ms) I_(DS)-V_(DS) characteristics. The Si_3N_4 passivation suppressed about 80% Z_D collapse in quiescent-bias-point stressed HEMTs. The remaining 20% I_D collapse were not suppressed which may be coming from buffer-related traps. However, more than 10% of I_D collapse suppression was observed on un-stressed or fresh-HEMTs. Similarly, improved cut-off frequency (f_τ), maximum oscillation frequency (f_(max)) and device output power (P_(out)) values were also observed on the un-stressed HEMTs. The Si_3N_4 passivation completely suppressed the I_D collapse in un-stressed or fresh-HEMTs which leads to 70% improvement in fr and 60% improvement in the device P_(out). The Si_3N_4 passivation did not completely suppress I_D 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.