by Curt H. Liebert and Ralph D. Thomas, NASA Lewis Research Center (Downloadable PDF File), APRIL 1968.

SUMMARY
“Measurements were made at temperatures of 300°, 882′, and 1074′ K of the normal was doped with a r s e n i c spectral emissivity of opaque, highly doped silicon. The silicon and boron to electron carrier concentrations of 2. 2X101′, 3. %lo1′, and 8 . 5 ~ 1 0 ~ ‘ electrons per cubic centimeter and hole carrier concentrationsof 6. 2X101′ and 1 . 4 ~ 1 0 holes per cubic centimeter. The 30 K emissivity data were obtained at wavelengths from 2.5 to 35 microns. The high temperature emissivities were measured from 3.5 to 1 4 . 8 microns. Carrier concentrations and direct-current resistivity of the silicon were also measured. The carrier concentrations were determined from Hall measurements made at 30 K. The direct-current resistivity was measured at temperatures from 30 to 1200’ K. These quantities (among others) were used in analytical calculations of the emissivities. Agreement of the Hagan-Rubens theory with experiment was found at wavelengths greater than 12 microns and at 30 K. Good agreement of the free carrier absorption theory with experiment w a s achieved at all wavelengths and temperatures investigated. The free carrier absorption theory predicts the emissivity in terms of the index of of these quantities are presented. A refraction and the absorption index. The values comparison of the values of the absorption index obtained herein with those obtained from the literature showed good qualitative agreement.”