INTERFACIAL REACTIONS BETWEEN RHODIUM AND GAAS IN BULK AND THIN-FILM FORM

Interfacial reactions between rhodium and GaAs in both thin film and bulk forms have been investigated in the temperature range 200-1000-degrees-C using transmission electron microscopy, energy-dispersive X-ray analysis, scanning electron microscopy and electron probe microanalysis. Thin film reaction behavior was consistent with the bulk diffusion couples which were annealed at higher temperatures and for longer times. In the thin film case, where the rhodium supply is limited, the final configuration is RhGa/RhAs2/GaAs. The diffusion path for bulk Rh/GaAs was determined to be Rh/RhGa/Rh2As/Rh12As7/RhAs/RhAs2/GaAs; however, before this final configuration was reached, a series of transient paths were observed which included supersaturated phases and two-phase structures. The diffusion path and reaction morphology have been rationalized using the phase diagram, kinetic observations and growth mechanisms observed during the reactions.