Thermoelectric properties of Ga1−xAlxAs

Theoretical and experimental results describing the dependence of the Seebeck and Peltier coefficients on the composition of Ga1−xAlxAs solid solution are given. The Seebeck coefficient for nondegenerately doped n- and p-type Ga1−xAlxAs is given by the simple expressions αn=(k/e)(lnNc/n+2) and αp=−(k/e)(lnNv/p+2), respectively. The dependence of α on the composition of Ga1−xAlxAs solid solutions is linear for p type and nonlinear for n type. This relation is dependent on the type of carrier that is involved in the conduction process, as well as the detailed band structure of the material. For p-type material, two kinds of carriers are involved: heavy and light holes; for n-type material, three kinds of carriers are involved: one direct electron and two indirect electrons. The direct electrons are dominant for Al composition of 0<x<0.3, and the indirect electron is dominant for composition 0.45<x<1. Experimental measurements of the Seebeck coefficient for n- and p-type Ga1−xAlxAs and for AuGe and AuZn resemble the theoretical results.