Atom-Probe Study of Al-Ga Exchange Reaction at Al-GaAs Interfaces

An atomically abrupt Al-GaAs interface was observed for Si-doped GaAs at 200 K by atom-probe mass spectroscopy. At 300 K an Al-As mixed layer having a low As concentration and containing no Ga was formed. Formation of the mixed layer at 200 K for Zn-doped GaAs could be attributed to a promoted reaction by Zn. A decrease in the thickness of the unreacted Al layer, an increase in the As concentration in the mixed layer with temperature, and the abrupt AlAs-GaAs interface indicate Al diffusion into GaAs and stable Al-As bonding.