A stoichiometric mixture of evaporating materials for CuInse 2 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, CuInse 2 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 620 ? Cand410 ? C , respectively. The temperature dependence of the energy band gap of the CuInse 2 obtained from the absorption spectra was well described by the Varshni's relation, E g (T)=1.1851eV?(8.99×10 ?4 eV/K)T 2 /(T+153K) . After the aa-grown CuInse 2 single crystal thin films was annealed in Cu-, Se-, and In-atmospheres, the origin of point defects of CuInse 2 single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of V cu ,V Se ,Cu int ,andSe int obtained by PL measurements were classified as a donors or accepters type. And we concluded that the heat-treatment in the Cu-atmosphere converted CuInse 2 single crystal thin films to an optical n-type. Also, we confirmed that In in CuInse 2 /GaAs did not form the native defects because In in CuInse 2 single crystal thin films existed in the form of stable bonds.