Study of GaN HEMTs electrical degradation by means of numerical simulations

In this paper, we investigate the effects of dc stress on GaN high-electron mobility transistors (HEMTs) by means of numerical simulations. Following stress tests showing a degradation of static characteristics (dc), the formation of an electron trap in the AlGaN barrier layer was related to the observed degradation according to the results obtained from numerical simulations carried out by introducing a trapping region underneath the gate edge. The worsening of the device dc performance is evaluated by changing the extension of the degraded region and the trap concentration while studying the variation of parameters like the saturated drain current I_DSS, the output conductance g_O, and the device transconductance g_M. An increase in the trap concentration induces a worsening of any of the above mentioned parameters; an increase in the extension of the degraded region induces a degradation of I_DSS and g_M, but can reduce g_O.