Low-temperature epitaxial growth of CoGe2(001)/GaAs(100) films using the partially ionized beam deposition technique

The partially ionized beam (PIB) deposition technique was used to deposit CoGe2(001) thin films heteroepitaxially on GaAs(100) substrates. The epitaxial arrangement is CoGe2(001)/GaAs(100). It is found that the best epitaxy was obtained with an ion energy around 1100 eV and with a substrate temperature of 280 °C. The wafers were treated only by immersion in HF:H2O 1:10 immediately prior to deposition. Contacts grown at the optimal epitaxial formation conditions displayed Ohmic behavior, while contacts grown at higher or lower substrate temperatures had rectifying behavior. Epitaxial formation of CoGe2, a high melting point, low resistivity cobalt germanide phase, offers the possibility of forming a stable contact to n-GaAs.