Influence of substrate temperature on the preparation of GaP thin films

Gallium phosphide (GaP) was prepared by treating specpure gallium with AnalaR grade Zn₃P₂ in an argon atmosphere. Thin films of GaP were evaporated onto glass substrates at various substrate temperatures under vacuum. Films evaporated onto substrates at and above 250°C were polycrystalline in nature. Films of various thicknesses were grown. The conductivity of these films in the dark and in white light is presented for the temperature range 100–300 K. Optical absorption spectra for films grown at substrate temperatures T_s = 90, 180 and 250°C were also recorded in the range 0.5–2.5 eV. All the features are attributed to the structural disorder which probably occurs during evaporation onto the glass substrates.