Photocurrent study on the splitting of the valence band and growth of CdIn2Te4 single crystal by Bridgman method
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수평 전기로에서C d I n 2 T e 4 다결정을 용응법으로 합성하고 Bridgman법으로 tetragonal structure의C d I n 2 T e 4 단견정을 성장시켰다. c축에 수직한 시료의 광흡수와 광전류 spectra를 293k에서 10K까지 측정하였다. Hall효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293 K에서 각각 8.61\times 10^{16}\textrm{cm}^3,\;242\textrm{cm}^V .s였다. C d I n 2 T e 4 단결정의 광흡수와 광전류 spectra를 293k에서 10K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap E g (T)는 Varshni 공식에 따라 계산한 결과1.4750 e v − ( 7.69 × 10 − 3 ) e v / k ) T 2 /(T + 2147k)이었다. 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting Δcr값이 0.2704 eV이며 spin-orbit Δ so값은 0.1465 eV임을 확인하였다. 10K일 때 광전류 봉우리들은 n : 1일때A 1 − B 1 − 와C 1 − -exciton봉우리임을 알았다
Abstract
A stoichiometric mixture for C d I n 2 T e 4 single crystal was prepared from horizontal electric furnace. The C d I n 2 T e 4 single crystal was grown in the three-stage vertical electric furnace by using Bridgman method. The C d I n 2 T e 4 single crystal was evaluated to be tetragonal by the power method. The (001) growth plane of oriented C d I n 2 T e 4 single crystal was confirmed from back-reflection Laue patterns. The carrier density and mobility of C d I n 2 T e 4 single crystal measured with Hall effect by van der Pauw method are 8.61 × 1016 cm − 3 and 242 cm 2 /V.s at 293 K, respectively. The temperature dependence of the energy band gap of the C d I n 2 T e 4 single crystal obtained from the absorption spectra was well described by the Varshni's relation, 1.4750 e v − ( 7.69 × 10 − 3 ) e v / k ) T 2 /(T + 2147k).The crystal field and the spin-orbit splitting energies for the valence band of the C d I n 2 T e 4 single crystal have been estimated to be 0.2704 eV and 0.1465 eV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Δ so definitely exists in the Γ 7 states of the valence band of the C d I n 2 T e 4 single crystal. The three photocurrent peaks observed at 10 K are ascribed to the A 1 − B 1 − and Cl-exciton peaks for n = 1.