Degradation mechanisms in heterostructure devices and their correlation with defects

The degradation mechanisms of GaAs-based heterojunction devices, PHEMTs and Beryllium and Carbon doped HBTs, are reviewed. In addition to the electrical characterization, two examples of complementary electrical and optical investigations are shown.The effect of hot-electron stress on the electrical devices properties of HEMTs is correlated to the variation of relative cathodoluminescence efficiency from source and drain area. As for HBTs, low temperature cathodoluminescence investigations show peak energy blue shifts after bias aging. These results support the hypothesis of stress induced Beryllium outdiffusion from the base into the emitter layer, as previously suggested by tie electrical measurements.