Scattering mechanisms in ${\mathrm{Hg}}_{1-x}{\mathrm{Cd}}_x\mathrm{Te}$

The calculation of electron-transport properties of ${\mathrm{Hg}}_{1-x}{\mathrm{Cd}}_x\mathrm{Te}$ has been generalized by using an accurate energy dispersion relation for the conduction electrons and by including the effects of electron-wave-function admixture, screening of lattice vibrations, and the degeneracy of the electron distribution. The drift and the Hall mobilities in the material are calculated for various values of $x$ at 300 as well as at 77°K. It is found that there remains a large discrepancy between the theory and the experimental data on mobility if one considers polar scattering by the longitudinal-optical vibrations of CdTe and HgTe in addition to scattering by acoustic modes (both deformation potential and piezoelectric types), ionized impurities, and heavy holes. Incorporation of alloy scattering improves agreement between theory and experiment at moderately large (but not small) values of $x$. The experimental results for all values of $x$ at 300 and also at 77°K can, on the other hand, be fitted with theory if in addition to the above scattering mechanisms, interaction with the transverse-optical phonons of HgTe is assumed to take place.