Temperature dependence of the refractive index of direct band gap semiconductors near the absorption threshold: Application to GaAs

Using a semiempirical model of the dielectric constant taking excitonic effects correctly into account, we calculate dn/dT for direct band gap semiconductors by separating the contribution of the excitonic enhancement near the band gap energy Eg from a background term described by the high frequency dielectric constant ε∞. Comparison of the model with experimental data suggests that dEg/dT≊−4.5×10−4 eV K−1 and dε∞/dT≊1.32×10−4 K−1 for GaAs at room temperature, a significant shift from the currently accepted values of these parameters.