Temperature Dependence of the Energy Gap in GaAs and GaP

Absorption measurements from 300°–973°K for GaAs and to 1273°K for GaP were made in order to determine the energy gap Eg of these materials at high temperatures. These data, together with previously published results, show that the energy-gap width may be represented by a simple expression for all temperatures. As a function of the absolute temperature T, the direct gap in GaAs is given by Eg=1.522−5.8×10−4T2 / (T+300) eV, and the indirect gap in GaP is given by Eg=2.338−6.2×10−4T2 / (T+460) eV. The general form of the expression for the energy gap is Eg=Eg(0)−aT2 / (T+β), where Eg(0) is the energy gap at 0°K, β is approximately the 0°K Debye temperature, and a is an empirical constant.