DEGRADATION OF LOW-FREQUENCY NOISE IN AlGaN/GaN HEMTS DUE TO HOT-ELECTRON STRESSING

We report on the degradation of low-frequency excess noise in recessed gate AlGaN/GaN HEMTs due to hot-electron stressing. The I-V characteristics and the low-frequency noise power spectral densities, Sv(f), of the open circuit voltage fluctuations across the drain source terminal were characterized with the stress time. Based on these results, we observed that the overall low-frequency noise degradation process can be identified to occur in two distinct phases. In the first phase, devices initially show fluctuations in the noise properties around a relatively constant average value. Detailed characterizations of the gate-source bias, V-GS, dependence of S-V(f) at cryogenic temperatures indicate signature-patterns in the variations of S-V(f) as a function of V-GS. This is shown to arise from the modulation of the percolation paths of the carriers in the two-dimensional electron gas (2 DEG). The onset of the second phase of degradation arises from the irreversible generation of interface states at the AlGaN/GaN hetero-interface.