Intrinsic carrier concentration of narrow-gap mercury cadmium telluride based on the nonlinear temperature dependence of the band gap

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Abstract
The intrinsic carrier concentrations of narrow‐gap Hg1−xCdxTe alloys have been calculated as a function of temperature between 0 and 300 K for x values between 0.17 and 0.30. The new and more accurate relation for the temperature dependence of the energy gap, which is based on two‐photon magnetoabsorption data, is used. This relation is further supported here by additional one‐photon magnetoabsorption measurements for x=0.20 and 0.23, which were made with a CO2 laser. In this range of composition and temperature, the energy gap of mercury cadmium telluride is small, and very accurate values for the gap are needed to obtain reliable values for the intrinsic carrier density. Kane’s k⋅p theory is used to account for the conduction‐band nonparabolicity. Large percentage differences occur between our new calculations and previously calculated values for ni at low temperatures. A nonlinear least‐squares fit was made to the results of our calculations for ease of use. The implications of these results for Hg1−xCdxTe materials characterization and device operations are discussed.