Physical Insights Into the Drain Current Injection-Induced Device Instabilities in AlGaN/GaN HEMTs

Through detailed experiments and well-calibrated computations, this work provides physical insights into the processes affecting the response of an AlGaN/GaN high electron mobility transistor (HEMT) to constant OFF-state drain current injection, a condition often encountered in circuit operation. Experiments reveal a stress time and stress current-dependent unique drain voltage evolution in response to a constant drain current injection. On the fly, dynamic ON-resistance and threshold voltage measurements are used to determine the role of trapping. Furthermore, calibrated computations are used to propose a mechanism involving a complex interplay of the processes of electron trapping in the surface and hole emission and electron trapping in the GaN buffer to explain the time-dependent evolution of drain voltage. Experimental validation of the mechanism is also provided by temperature, passivation thickness, and light exposure-dependent analysis, as well as by experimentation on devices with variations in buffer carbon doping.