Intrinsic absorption and photoconductivity in single crystal SiTe2

Optical absorption in single crystal SiTe2 has been studied at 300°K throughout the wavelength range 0·3–10 μ. Platelet type samples were prepared by iodine vapor transport. On the basis of the absorption measurements SiTe2 has been classified as an indirect gap semiconductor with a threshold for phonon assisted transitions in the neighborhood of 1·85 eV. An analysis of the functional dependence of the fundamental absorption edge on photon energy indicates the existence of a direct transition with a band gap at 2·18 eV. Photoconductive spectral response curves show a peak response at 2·16 eV. The photoresponse observed away from the direct band gap has been attributed to the effects of rapid chemical decomposition which is known to occur on the surface of crystalline SiTe2.