Theory of carrier mobility in polar semiconductors-II. Solid solutions

Abstract

In part I of this series, the mobility problem of polar semiconductors was analysed by invoking two-phonon multiband conduction processes which involved inter-band transition of the carriers. In the present paper the theory is extended to solid solutions of the systems where the perturbations arising out of alloying effects also lead to inter-band transition effects and assist in the multiband conduction of carriers. One phonon scattering processes for the carrier with the acoustic modes coupled with the modification of carrier state functions by alloying effect are considered in the transport problem. The expression of mobility in the low temperature region is of the form μ = μ 0^(s)T^-3/2 (T > 50° K) which gives the right temperature and concentration dependence; here μ0^(s) is a function of concentration of the components. It is shown that in the high temperature region the two phonon processes dominate giving μ ∞ T^-5/2 dependence. The theoretical predictions conform very closely with the experimental results of some systems (e.g. PbTe-PbSe, and Bi₂Te₃-Bi₂Se₃).