Thin films of Ni, Ge, and Ti were evaporated onto n-GaAs to investigate the correlation between solid-phase interfacial reactions and development of ohmic contacts. Initially 65 nm Ni films were electron beam deposited onto the GaAs substrate and vacuum annealed in situ at 300 °C to produce a ∼130-nm-thick Ni2.4GaAs phase. After Ni2.4GaAs was produced, 30 nm of Ge and 25 nm Ti films were deposited and vacuum annealed at 500 °C. This resulted in solid phase epitaxial regrowth of ∼30 nm of GaAs from decomposition of Ni2.4GaAs first into NiAs and NixGa with subsequent decomposition of these binary phases into NiTiy and GaAs. Similar structures without the in situ annealing (i.e., sequentially deposited Ni, Ge, and Ti, all annealed simultaneously at 500 °C) were studied for comparison. Only the in situ annealed structure showed ohmic behavior after annealing at 500 °C for 5 min, and only when Ge was incorporated into regrown GaAs. © 1999 American Institute of Physics.