Degradation mechanism of the nonspiking ohmic contacts formed by solid-phase regrowth process on n-GaAs

The thermal stability of the Ge/Pd and the Pd-In-Ge ohmic contacts on n-GaAs formed by the solid-phase regrowth process has been investigated. It was found that degradation of these contacts at elevated temperatures cannot be rationalized by a single degradation process. The degradation at different temperatures can be best described by two processes: (a) a diffusion-controlled process and (b) a reaction-controlled process. The experimental results show that the thermal stability of the contacts can be improved by SiNx capping layers when the reaction-controlled process is the most significant process; however, SiNx capping layers cannot improve their thermal stability if the diffusion-controlled process is the dominant degradation process at elevated temperatures.