Field and Temperature Dependent Life-Time Limiting Effects of Metal-GaAs Interfaces of Device Structures Studied by XPS and Electrical Measurements

Typical Schottky contacts for GaAs devices such as Al and TiPtAu metallizations have been accelerated-stress tested under bias at room temperature and at temperatures up to 250° C. The influence of these stress tests on the interface properties were studied by XPS sputter profiling and correlated with electrical measurements. Concerning Al-contacts it has been found that bias-stressing results in a structural change of the Al layer and that the oxygen concentration at the Al-GaAs transition depends both on the polarity of bias stressing and on the GaAs surface treatment before Al-metallization. These effects are quite pronounced even at room temperature. TiPtAu contacts are stable at room temperature over the period of investigation (200 h) but at elevanted temperatures (200° C) a GaAs diffusion into Ti and a subsequent Ti diffusion into Ga vacancies could be observed. This results in a catastrophic bias dependent degradation of the I/V characteristics.