DISPERSION OF THE REFRACTIVE INDEX OF LIGHT AND PERMITTIVITY OF GALLIUM PHOSPHIDE.

Measurements of the refractive index of n- and p-type GaP doped to give carrier densities of N equals 0. 5 multiplied by (times) 10**1**6 minus 0. 7 multiplied by (times) 10**1**9 cm** minus **3 were made in the spectral range lambda equals 0. 5-25 mu at temperatures of 100-420 degree K. The dispersion curve was calculated and experimental results agreed to within 0. 2% at lambda equals 0. 5-4 mu and to within 0. 8% in the range lambda greater than 4 mu . The model employed made it possible to determine independently the high-frequency epsilon // infinity and low-frequency epsilon //0 permittivities, which were epsilon // infinity equals 9. 075 and epsilon //0 equals 11. 02 at T equals 297 degree K and epsilon // infinity equals 8. 963 and epsilon //0 equals 10. 88 at T equals 105 degree K. A study was made of the influence of impurities on the refractive index. The specific example of GaP:Te was used to demonstrate that, at low temperatures, the presence of impurities could give rise to anomalous dispersion of the refractive index. 13 refs.