Hot Wall Epitaxy(HWE)법에 의한 AgGaSe2 단결정 박막 성장과 가전자대 갈라짐에 대한 광전류 연구
Growth and study on photocurrent of valence band splitting for AgGaSe2 single crystal thin film by hot wall epitaxy
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Abstract
Single crystal AgGaSe2 layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at 420oC with hot wall epitaxy (HWE) system by evaporating AgGaSe2 source at 630oC. 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 single crystal AgGaSe2 thin films measured with Hall effect by van der Pauw method are 4.051016 /cm3, 139cm2/V s at 293K, 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) = 1.9501eV (8.79104 eV/K)T2/(T + 250K). The crystal field and the spin-orbit splitting energies for the valence band of the AgGaSe2 have been estimated to be 0.3132eV and 0.3725eV at 10K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the So definitely exists in the 5 states of the valence band of the AgGaSe2. The three photocurrent peaks observed at 10K are ascribed to the A1-, B1-, and C1-exciton peaks for n = 1.
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