Photocurrent study on the splitting of the valence band and growth of ZnIn₂Se₄single crystal thin film by hot wall epitaxy
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A stoichiometric mixture of evaporating materials for ZnIn₂Se₄single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, ZnIn₂Se₄ 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 400℃, 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 ZnIn₂Se₄single crystal thin films measured from Hall effect by van der Pauw method are 9.41 × 1016 cm-³ and 292 cm²/v · s at 293 K, respectively. The temperature dependence of the energy band gap of the ZnIn₂Se₄obtained from the absorption spectra was well described by the Varshni’s relation, Eg(T) = 1.8622 eV − (5.23 × 10−4 eV/K)T2/(T + 775.5 K). The crystal field and the spinorbit splitting energies for the valence band of the ZnIn₂Se₄have been estimated to be 182.7 meV and 42.6 meV,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 ZnIn₂Se₄/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the A1-, B1-exciton for n = 1 and C27-exciton peaks for n = 27.
Abstract
A stoichiometric mixture of evaporating materials for ZnIn₂Se₄single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, ZnIn₂Se₄ 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 400℃, 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 ZnIn₂Se₄single crystal thin films measured from Hall effect by van der Pauw method are 9.41 × 1016 cm-³ and 292 cm²/v · s at 293 K, respectively. The temperature dependence of the energy band gap of the ZnIn₂Se₄obtained from the absorption spectra was well described by the Varshni’s relation, Eg(T) = 1.8622 eV − (5.23 × 10−4 eV/K)T2/(T + 775.5 K). The crystal field and the spinorbit splitting energies for the valence band of the ZnIn₂Se₄have been estimated to be 182.7 meV and 42.6 meV,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 ZnIn₂Se₄/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the A1-, B1-exciton for n = 1 and C27-exciton peaks for n = 27.
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