| 초록 |
A stoichiometric mixture of evaporating materials for AgGaSe2 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, AgGaSe2 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 630℃ and 420℃, respectively. The temperature dependence of the energy band gap of the AgGaSe2 obtained from the absorption spectra was well described by the Varshni's relation, Eg(T) = 1.9501 eV - (8.79 × 10-4 eV/K)T2/(T + 250 K). After the as-grown AgGaSe2 single crystal thin films was annealed in Ag-, Se-, and Ga-atmospheres, the origin of point defects of AgGaSe2 single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of VAg, VSe, Agint, and Seint obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted AgGaSe2 single crystal thin films to an optical p-type. Also, we confirmed that Ga in AgGaSe2/GaAs did not form the native defects because Ga in AgGaSe2 single crystal thin films existed in the form of stable bonds. |
