Comparative reliability study of GaAs power MESFETs Mechanisms for surface-induced degradation and a reliable solution

An experimental investigation of the reliability of 250 commercially available power FETs (0.5-1.5 W) is presented. Mechanisms for surface-induced degradation were identified, based on the performance characteristics of the devices under the following test conditions: dc operation at channel temperatures of 205 and 265 C; gate reverse bias at 150 C; and RF drive at 8 GHz and at channel temperatures in the range 120-140 C. Microwave and dc parameters were determined for each set of test conditions. It is found that: (1) long degradation of SiO2-protected GaAs power FETs can be explained in terms of the oxidation of GaAs in the recessed and nonrecessed access regions; and (2) when a plasma-enhanced silicon nitride film was vapor-deposited on some of the degraded FETs, the time-dependent drift of RF gain was eliminated.