High-field effects in silicon nitride passivated GaN MODFETs

This paper presents a detailed study of high-field effects in GaN MODFETs. Degradation of de characteristics and change of flicker noise due to hot electron and high-reverse current stresses in Si3N4 passivated GaN MODFETs have been investigated. The authors observe that during hot electron stress, electron trapping in the barrier layer and interface state creation occur. These cause a positive shift of V-t, reduce I-D, skew the transfer characteristics, and degrade g(m). Flicker noise (1/f) measurements show that after hot electron stress, the scaled drain current noise spectrum (SID/ID2) decreases in depletion, but increases Only slightly in strong accumulation, corroborating the creation of interface states but only a small creation of transition-layer tunnel traps that contribute to 1/f noise. During high-reverse current stress, electron trapping dominates for the first 50-60 s and then hole trapping and trap creation begin to manifest. However, there. still is net electron trapping under the gate after one hour of stress. The degradation processes bring about a positive shift of V-t, degrade I-D and g(m), and increase reverse leakage. After high-reverse current stress, S-ID/I-D(2). increases substantially in strong accumulation, indicating the creation of transition layer tunnel traps.