Temperature and composition dependence of the energy gap of Hg1−<i>x</i>Cd<i>x</i>Te by two-photon magnetoabsorption techniques

Abstract

Accurate determinations of the energy gap Eg at liquid helium temperatures in alloys of 0.24≤x≤0.30 have been made by two-photon magnetoabsorption techniques. They are shown to help verify the use of the Hansen–Schmit–Casselman (HSC) relation over the range 0&amp;lt;x&amp;lt;0.30 at these temperatures. In contrast, the observed temperature dependence of Eg below 77 K is nonlinear and thus cannot be described accurately by the HSC relation. Analysis of Eg (T) data for three samples with 0.24≤x≤0.26 has allowed the deduction of a new relationship for Eg (x,T) that more properly accounts for the nonlinear temperature dependence below 77 K and the linear behavior above 77 K, while still accurately describing the x dependence Eg(x,T) =−0.302 +1.93x +5.35(1−2x)(10−4) [(−1822+T 3)/(255.2+T 2)] −0.810x2 +0.832x3, for Eg in eV and T in K. This relation should apply to alloys with 0.2&amp;lt;x&amp;lt;0.3. The maximum change from the HSC relation in this range is 0.004 eV for x=0.2 at ∼10 K.