An Investigation of the Electrical Degradation of GaN High-Electron-Mobility Transistors by Numerical Simulations of DC Characteristics and Scattering Parameters

The effects of direct-current (DC) stress on GaN high-electron-mobility transistors (HEMTs) are investigated by means of numerical simulations, by which the creation of an acceptor trap in the AlGaN barrier layer was correlated to the observed experimental degradation. An increase in the trap concentration induces a worsening of the saturated current I _DSS, transconductance g _m, and output conductance g _O. An increase in the length of the trapping region induces a degradation of I _DSS and g _m, but can reduce g _O. Analysis of scattering parameters in the saturation region shows that the cutoff frequency f _T matches the trend of g _m.