Atomic distributions across metal–III-V-compound-semiconductor interfaces

Abstract

The distribution of atomic species across metal–III-V-compound-semiconductor interfaces has been studied with ${\mathrm{Ar}}^{+}$-ion bombardment and x-ray photoemission complemented by synchrotron radiation photoemission. Results for (Ti, Cr, Co, Au)/GaAs, (Co, Cr)/InP, and (Cr, Au)/InSb show that room-temperature metal deposition induces substrate disruption. The details of reactions at these interfaces then play a critical role in determining the distribution of semiconductor atoms in the overlayers. Strong metal-anion reactions cause the expulsion of cations from regions where there is compound formation, and there is a characteristic coverage at which this occurs. The result is a cation-deficient region near the buried interface. Weak metal-anion reactions cause no such long-range species redistribution, except for surface segregation. For Au–III-V interfaces, there is an onset for anion surface segregation as a nearly pure Au layer decorated by semiconductor atoms in supersaturation evolves from the Au-anion-cation mixture found at low coverage. The driving force for atomic redistribution is the lowering in energy of the system, but this is restricted by kinetics and diffusion at low temperature. Studies for Cr/GaAs show the effect of altering the temperature and, hence, the amount of diffusion.