Energy gap versus alloy composition and temperature in Hg_{1 -x}Cd_xTe

An empirical expression for the energy band gap E_g of Hg _1-xCd_xTe versus the temperature and alloy composition, deduced from optical absorption data for thin samples with different composition x, is reported as E_g =-0.295+1.87x-0.28x²+(6-14x+3x ²) (10^-4)T+0.35x⁴, which is applicable to the ranges of 0≤x≤0.37 (plus x=1) and 4.2≤T≤300 K. The values E_g of this expression are uniformly higher than the expressions of Hansen, Schmit, and Casselman. By comparing both expressions with the known magneto-optical experimental data at 4.2 and 24 K, we find that for this expression the standard error of estimate is 0.008 eV which is better than the expression of Hansen et al.