Epitaxial layers of CuInSe2 on GaAs

CuInSe₂ single-crystal films with (112) orientation and with thicknesses in the range 800–1200 Å were deposited onto semi-insulating (111)A-oriented GaAs substrates by flash evaporation under controlled growth conditions. Epitaxial growth began at a substrate temperature T_sub = 720 K and twins in the 〈221〉 direction were detected in reflection high energy electron diffraction investigations. The twin concentration decreased with increasing growth temperature. At T_sub = 870 K a change of the structure from chalcopyrite to sphalerite was observed. Films produced at T_sub ? 720 K showed n-type conductivity whereas at higher growth temperatures the films were always p type and showed a rapid increase in hole concentration with increasing substrate temperature. Two different acceptor levels with ionization energies of 92 meV and about meV were found.