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CuAlSe2 is a wide-gap material with chalcopyrite structure and has potential applications on optoelectronic devices. In this work, CuAlSe2 thin films are prepared by three-source evaporation. The film formation processes are similar to those of CuInSe2, i.e. two binary phases formed first and then reacted to form the ternary compound. Single-phase of CuAlSe2 can be obtained at a substrate temperature above 650oC while the ratio of Cu/Al source flux is kept higher than 1. A Cu-rich film is p-type and has a resistivity about 0.15 Ohm-cm. PL spectra show two strong free-to-bound transmissions peaked at 2.63 and 2.66 eV and one weak defect band at 2.00 eV. The emission peak at 2.66 eV may be related to Se vacancies since it diminishes after annealing in Se vapor. A XRD study indicates that there is no significant interdiffusion between CuAlSe2 and CuInSe2 at a temperature below 680oC. This suggests that this material may form a heterojunction with other Cu-III-Se2 compounds. |