Analysis of surface-induced degradation of GaAs power MESFET's

Long-term degradation of GaAs power MESFET's is shown to be surface induced. Using micro-Auger analysis (beam spot size ≃0.1-0.2 µm), we have identified a gallium outdiffusion induced by the SiO
2
surface protection deposition and a GaAs oxidation mechanism during electrical operation. These reactions modify the electrical surface properties in the access regions explaining the RF and dc performances degradation.