Refractive indexes of ZnSe, ZnTe, and CdTe were obtained from prism refraction data and are reported for a series of wavelengths from 2.5 μ to the short-wave transmission limits set by the band gaps. The results were fitted with the standard formula: n2=A +[Bλ2/(λ2−c2)] where n is the refractive index and λ is the wavelength in microns. For ZnSe the best values of the parameters are A=4.00, B=1.90, and c2=0.113; for ZnTe, A=4.27, B=3.01, and c2=0.142; and for CdTe, A=5.68, B=1.53, and c2=0.366. Possible causes for the discrepancies between the present results and earlier data are discussed.

The refractive index of GaAs, as measured by the prism refraction method, is reported here for photon energies from 0.7 eV up to the absorption limit set by the band gap, for temperatures of 300°, 187°, and 103°K. The results are compared with the previous data (obtained only for room temperature), and are used to show that the spacing of emission lines of GaAs lasers corresponds to that of the axial modes of a Fabry-Perot resonator.

Single crystals of ZnSe have been prepared by the vapor growth technique and optical and electrical measurements on these crystals are reported. Analysis of the reststrahlen reflection peak gives 0.026 ev for the transverse optical phonon energy. The longitudinal optical phonon energy is 0.031 ev as calculated from the transverse phonon energy, the static dielectric constant, ε0=8.1±0.3, and the high-frequency dielectric constant, ε∞=5.75±0.1. The effective ionic charge calculated from the Szigetti formula is 0.7±0.1. Exciton absorption peaks associated with the valence and conduction bands in the vicinity of Γ were observed at liquid hydrogen temperature with the principal peak at 2.81±0.01 ev. The exciton reduced mass 0.1 m0 combined with the room temperature electron-to-hole mobility ratio of 12, obtained by preliminary transport measurements on n- and p-type ZnSe gives tentative values of 0.1 m0 and 0.6 m0 for the electron and hole masses, respectively. Reflectance was determined by various methods in the range 0.025 to 14.5 ev photon energy and was analyzed by the Kronig-Kramers inversion method to obtain the optical constants in the 1 to 10 ev range. A number of peaks appear in the imaginary part of the dielectric constant. The first set of peaks, 2.7 and 3.15 ev, are believed to be due to exciton and interband transitions at Γ with a spin-orbit valence band splitting of 0.45 ev. The second set of peaks, 4.75 and 5.1 ev, are tentatively assigned to transitions at L with a spin-orbit splitting of 0.35 ev. Other peaks are observed at higher energies.

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