Concentration dependence of the refractive index for <i>n</i> - and <i>p</i> -type GaAs between 1.2 and 1.8 eV

The refractive indices of GaAs at room temperature were determined from accurate double-beam reflectance measurements. The uncertainty in the refractive indices obtained by this technique is ±0.005. Measurements were made on high-purity n -type samples, n -type samples with free-electron concentrations from 5×1016 to 6.7×1018 cm−3, p -type samples with free-hole concentrations from 1.5×1016 to 1.6×1019 cm−3, and p -type samples heavily doped with the amphoteric impurity Si. These data agree with Marple's prism refractive data for both of his samples of the same impurity concentration. Analysis of the reflectance for the high-purity samples permitted assignment of the room-temperature energy gap as 1.424±0.001 eV. The shape of the refractive-index-vs-energy curve was found to be strongly dependent on the carrier concentration at energies near the direct energy gap.