Growth and Optical Conductivity Properties for BaAl2Se4 Single Crystal Thin Film by Hot Wall Epitaxy

Title & Authors
Growth and Optical Conductivity Properties for BaAl2Se4 Single Crystal Thin Film by Hot Wall Epitaxy
Jeong, Junwoo; Lee, Kijung; Hong, Kwangjoon;

Abstract
A stoichiometric mixture of evaporating materials for $\small{BaAl_2Se_4}$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $\small{BaAl_2Se_4}$ 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 $\small{610^{\circ}C}$ and $\small{410^{\circ}C}$, 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 $\small{BaAl_2Se_4}$ single crystal thin films measured from Hall effect by van der Pauw method are $\small{8.29{\times}10^{-16}cm^{-3}}$ and $\small{278cm^2/vs}$ at 293 K, respectively. The temperature dependence of the energy band gap of the $\small{BaAl_2Se_4}$ obtained from the absorption spectra was well described by the Varshni's relation, $\small{E_g(T)=3.4205eV-(4.3112{\times}10^{-4}eV/K)T^2/(T+232 K)}$. The crystal field and the spin-orbit splitting energies for the valence band of the $\small{BaAl_2Se_4}$ have been estimated to be 249.4 meV and 263.4 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the $\small{{\Delta}so}$ definitely exists in the $\small{{\Gamma}_5}$ states of the valence band of the $\small{BaAl_2Se_4/GaAs}$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $\small{A_1}$-, $\small{B_1}$-exciton for n =1 and $\small{C_{31}}$-exciton peaks for n=31.
Keywords
$\small{BaAl_2Se_4}$ single crystal thin films;Energy band gap;photocurrent spectum;Crystal field splitting energy;Spin-orbit energy;
Language
Korean
Cited by
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