A theoretical and experimental study of the energy bandgap in MBE-grown Hg_1-xCd_xSe

Temperature-dependent infrared transmission spectroscopy has been applied to study the optical properties of Hg_0.815Cd_0.185Se thin film grown by molecular beam epitaxy on GaSb (2 1 1)B substrate. Discrepancies were observed between the measured optical bandgaps and the calculated values based on the previously reported empirical expression for the energy bandgap E_gx,T of Hg_1-xCd_xSe. A new empirical expression has been established based on ab initio calculations, and the results are shown to be in a good agreement with the experimental data of this study. By comparing both expressions with all of known experimental data for x ≤ 0.354 from other studies over the temperature range of 0 < T < 310 K, it is found that for the new expression presented in this study, the standard error between calculations and experimental data is 0.010 eV which is comparable to that of the previously reported expression for Hg_1-xCd_xSe with 0.194 ≤ x ≤ 0.354 and is approximately 50% more accurate for 0 ≤ x ≤ 0.19.