J. W. Jeong

A Study on the Splitting of the Valance Band for a CdIn2te4 Single Crystal Using Photocurrent Measurement

The p‐CdIn2Te4 single crystal has been grown by using Bridgman method without a seed crystal in a three‐stage vertical electric furnace. From the photocurrent measurement, it was found that the three peaks of A, B, and C corresponded to the intrinsic transition due to the band‐to‐band transition from the valence band state Γ 7(A), Γ 6(B), and Γ 7(C) to the conduction band state Γ 6, respectively. Also, the valence band splitting of the CdIn2Te4 crystal has been first confirmed through the photocurrent spectroscopy. The crystal field splitting and the spin orbit splitting were obtained to be 0.2360 and 0.1119 eV, respectively. Also, the temperature dependence of the band gap energy of the CdIn2Te4 crystal has been driven as the following equation of Eg(T) = Eg(0) − (9.43 × 10−3)T2/(2676 + T). In this equation, the Eg(0) was estimated to be 1.4750, 1.7110, and 1.8229 eV at the valence band state A, B, and C, respectively. The band gap energy of the p‐CdIn2Te4 at room temperature was determined to be 1.2023 eV.

Photocurrent Study on the Splitting of the Valence Band and Growth of BaIn 2 Se 4 epilayers by Hot Wall Epitaxy

A stoichiometric mixture of evaporating materials for BaIn2Se4 epilayers was prepared from horizontal electric furnace. To obtain the single crystal thin films, BaIn2Se4 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 o C and 400 o C, respectively. The crystalline structure of the epilayers was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of BaIn2Se4 epilayers measured from Hall effect by van der Pauw method are 8.94×10 17 cm -3 and 343 cm 2 /vs at 293 K, respectively. The temperature dependence of the energy band gap of the BaIn2Se4 obtained from the absorption spectra was well described by the Varshnis relation, Eg(T)=2.6261 eV-(4.9825×10 -3 eV/K)T 2 /(T+558 K). The crystal field and the spin-orbit splitting energies for the valence band of the BaIn2Se4 have been estimated to be 116 meV and 175.9 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 states of the valence band of the BaIn2Se4/ GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the A1-, B1-exciton for n = 1 and C21-exciton peaks for n=21.

Photocurrent Study on the Splitting of the Valence Band and Growth of CuAlSe 2 Single Crystal Thin Film by Hot Wall Epitaxy

A stoichiometric mixture of evaporating materials for MgGa2Se4 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, MgGa2Se4 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 610 o C and 400 o C, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the MgGa2Se4 obtained from the absorption spectra was well described by the Varshnis relation, Eg(T) = 2.34 eV − (8.81 × 10 −4 eV/K)T 2 /(T + 251 K). The crystal field and the spin-orbit splitting energies for the valence band of the MgGa2Se4 have been estimated to be 190.6 meV and 118.8 meV, 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 Γ5 states of the valence band of the MgGa2Se4/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.

A Study on Properties of Infrared Detector for a HGCDTE Epilayers Using Photocurrent Measurement

Hg1−xCdxTe (MCT) was grown by hot wall epitaxy. Prior to the MCT growth, the CdTe (111) buffer layer was grown on the GaAs substrate at the temperature of 590 °C for 15 min. When the thickness of the CdTe buffer layer was 5 μm or thicker, the full width at half maximum values obtained from the x‐ray rocking curves were found to significantly decrease. After a good quality CdTe buffer layer was grown, the MCT epilayers were grown on the CdTe (111) /GaAs substrate at various temperatures in situ. The crystal quality for those epilayers was investigated by means of the x‐ray rocking curves and the photocurrent experiment. The photoconductor characterization for the epilayers was also measured. The energy band gap of MCT was determined from the photocurrent measurement and the x composition rates from the temperature dependence of the energy band gap were turned out.