Excitonic emissions from CuInSe2 on GaAs(001) grown by molecular beam epitaxy

CuInSe2 epitaxial films grown on (001)‐oriented GaAs substrates by molecular beam epitaxy have been characterized by means of low temperature photoluminescence spectroscopy at T=2–102 K. Distinct emission lines were observed near the band gap, and have been investigated further with varying sample temperature. An emission at 1.0386 eV (EX1) became broader with increasing sample temperature, and still remained up to T=102 K. A distinct, sharp emission at 1.0311 eV (IX1) which disappeared at a significantly lower temperature than the other peaks was observed only in films with weak donor‐related emissions. We attribute such emissions to the ground‐state free exciton [FEn=1] and exciton bound to neutral acceptor [A0,X], respectively. The band gap of CuInSe2 epitaxial films was also determined to be Eg=1.046 eV at 2 K using the reported exciton binding energy of Eex=7 meV.