Analysis of hot carrier aging degradation in GaN MESFETs

In this paper the study of the effects of illumination on the drain current of GaN MESFETs are presented with the aim of discriminating effects due to traps on the device sUiface from those related with epitaxial material substrate and its inteifaces. Illumination together with on-state stress are also used to investigate hot carrier degradation phenomena which consist in drain access resistance increase and consequently in drain CUfTent decrease: this can be attributed to the generation of deep levels andlor to increased trapped chilrge after hot-carrlertest on the device suiface access regions between the gate and the drain contacts. The degradation level is remarkably higher in un passivated devices with respect to . passivated ones. Hot carrier degradation can be recovered by thermal or R. T. storage without bias.