Analysis of RTN Induced by Forward Gate Stress in GaN HEMTs with a Schottky p-GaN Gate

In this work, a random telegraph noise (RTN) analysis has been carried out, to the best of our knowledge, for the first time to characterize the defects activated by forward-biased gate stress in GaN-HEMTs with metal/pGaN Schottky gate. The RTN signal has been measured for both gate leakage (IG) and drain current (ID), after each stress phase until the occurrence of the time-dependent gate breakdown. By analyzing the power spectral density (PSD) of post-stress currents, four 1/f2 components, featuring different amplitude and time constants, were observed. In contrast, the PSD derived from fresh currents does not display segments with 1/f2 trend. Three RTN components have been observed on both IG and ID, suggesting defect/s in the AlGaN barrier or at the AlGaN/GaN interface, whereas the fourth one showed up only on IG, could be possibly related to defects at the Schottky junction.