| 초록 |
A stoichiometric mixture of evaporating materials for CuAlSe2 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, CuAlSe2 mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were 680℃ and 410℃, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CuAlSe2 single crystal thin films measured with Hall effect by van der Pauw method are 9.24×1016 cm-3 and 295 cm2/V·s at 293K, respectively. The temperature dependence of the energy band gap of the CuAlSe2 obtained from the absorption spectra was well described by the Varshni's relation, Eg(T) = 2.8382 eV - (8.68 × 10-4 eV/K)T2/(T + 155K). The crystal field and the spin-orbit splitting energies for the valence band of the CuAlSe2 have been estimated to be 0.2026 eV and 0.2165 eV at 10K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Δso definitely exists in the Γ5 states of the valence band of the CuAlSe2. The three photocurrent peaks observed at 10K are ascribed to the A1-, B1-, and C1-exciton peaks for n = 1. |
