Random telegraph noise (RTN) and pre-breakdown bursts in gate current are studied in time domain in degraded AlGaN/GaN HEMTs subjected to reverse bias stress. Analysis of RTN under both forward and reverse gate bias indicates that the origin of RTN is due to modulation of current via a stress-induced percolation path by a trap. At voltages close to the device breakdown voltage, large amplitude pre-breakdown bursts have been observed. Their origin is discussed in terms of dielectric wear out of passivation layer at the gate edge
