Lifetesting GaN HEMTs With Multiple Degradation Mechanisms

A technique is described, to efficiently evaluate the reliability of an RF semiconductor device when several different mechanisms contribute simultaneously to its wearout. This is of interest for present-day GaN HEMT devices because symptoms of several simultaneous degradation mechanisms have been reported widely. The technique involves first finding DC parameters that are “signatures” of each mechanism. Then, separate DC-stress lifetests are performed to find the degradation rates for the signature parameters, at several temperatures, and the corresponding Arrhenius curves. Next, an RF-stress lifetest (with only one stress condition) is performed, while monitoring all of the signature parameters and the RF performance. This is utilized to determine the “scaling factors” between the rates of change in the DC lifetests and the rates of change in the RF application. Applying these scaling factors to the original Arrhenius curves gives an “overall” Arrhenius plot for the RF application with several different lines, for the different degradation mechanisms. The technique can be extended to further degradation mechanisms, by conducting further DC and RF lifetests while monitoring appropriate signature parameters.