Interfacial interactions of evaporated iridium thin films with (100) GaAs

We report a systematic study of thermally activated solid phase reactions between (100) GaAs and evaporated iridium thin films (100 and 550 Å thick). The investigation is carried out with Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Interfacial interactions are observed after annealing the system at temperatures higher than 500 °C. Complete reaction at 700 °C results in the formation of Ir₃Ga₅ and IrAs₂ phases. Intermediate phase IrGa is formed in the annealing temperature range of 500-650 °C. Vertical phase segregation is also observed with the IrAs₂ phase at the interface and the Ir-Ga phases on the surface layer. Specific information on the reaction kinetics, transformation, and structures of different phases and phase distributions are also discussed. Comparisons with interfacial reactions of other near noble metal/GaAs systems are presented. Based on the metallurgical information obtained, the potential applications of this contact system are suggested.