Epitaxial CuGaSe 2 Thin Films − Removal of Cu 2− x Se Secondary Phase From Film Surface

Cu‐rich CuGaSe 2 (CGS) thin layers were prepared on GaAs (100) and stepped GaAs (111)A substrates by molecular beam epitaxy (MBE). The presence of a Cu/Cu 2−x Se binary phase was observed and verified by XPS/UPS. By annealing the CGS samples subsequently at 600 °C growth temperature for 10 min, the secondary phase was removed while the Cu/Ga ratio decreased to a near stoichiometric value. Thus, the annealing step causes a reformation of the surface and surface structure, which could also be observed by LEED. Thereby the prior (4 × 2) reconstruction of the zinc blende order for the CGS [001] direction becomes sharper and more pronounced after the annealing step. For the [112] direction a (1 × 1) chalcopyrite reconstruction prior to the annealing step was changed into a clear (3 × 1) reconstruction after annealing the sample.