We have used the data from 22 different studies to derive a new empirical expression for the energy band gap (Eg) of Hg1−xCdxTe: Eg =−0.302+1.93x+5.35(10−4)T(1−2x) −0.810x2+0.832x3. This expression is valid over the full composition range and for temperatures from 4.2 to 300 K. The standard error of estimate is 0.013 eV, which is at least 15% better than that of previously reported expressions.

Intrinsic carrier concentration in Hg1−xCdxTe is calculated as a function of temperature and composition using the Kane nonparabolic approximation for band structure and recent measurements of the heavy hole mass mh and energy gap Eg. An expression fitted to these calculations is: ni[5.585−3.820x+1.753(10−3)T −1.364(10−3)xT] ×(1014)E3/4gT3/2 exp(−Eg/2kbT). The fit of this approximation is within 1% of the calculated ni for the range Eg>0, 50<T<300 K and x<0.7. It is also within 15% of experimental ni obtained from Hall measurements.

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The temperature and compositional dependences of the energy gap are determined for the alloy semiconductor mercury-cadmium telluride (Hg1−xCdxTe). The cutoff wavelength was measured on photoconductive and photovoltaic infrared detectors where 0.17<x<0.60 over a temperature range 20<T< 300°K. Spectral response curves are shown to indicate the precision of the method. The temperature and compositional dependences of the energy gap are shown and the empirical expression Eg (eV) =1.59x−0.25+5.233(10−4)T(1−2.08x)+0.327x3is deduced.

The intrinsic carrier concentration, reduced Fermi energy, electron effective mass, and the Fermi energy with and without doping are calculated for Hg1_zCd x Te with x>0.16 and 50< T < 350 o K. The calculations take into account the nonparabolicity of the bands by using the k·p method (Kane model) to determine n and by using the most recent linear temperature dependence of the bandgap. By fitting the n, curves calculated for nonparabolic bands to the expression for parabolic bands, the following approximation for the intrinsic carrier concentration was obtained: n;= (1.093-0.296x+0.OO0442T) 5.16(10 14 ) (Eg) 314 (T)8/' exp( -E o /2kT).