The refractive indices of GaAs at room temperature were determined from accurate doublehyphen;beam reflectance measurements. The uncertainty in the refractive indices obtained by this technique is plusmn;0.005. Measurements were made on highhyphen;puritynhyphen;type samples,nhyphen;type samples with freehyphen;electron concentrations from 5times;1016to 6.7times;1018cmminus;3,phyphen;type samples with freehyphen;hole concentrations from 1.5times;1016to 1.6times;1019cmminus;3, andphyphen;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 highhyphen;purity samples permitted assignment of the roomhyphen;temperature energy gap as 1.424plusmn;0.001 eV. The shape of the refractivehyphen;indexhyphen;vshyphen;energy curve was found to be strongly dependent on the carrier concentration at energies near the direct energy gap.
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