OPTICAL-PROPERTIES OF UNDOPED AND CHROMIUM-DOPED V-A-VIA-VIIA SINGLE-CRYSTALS

SbSl:Cr, SbSel:Cr, BiSI:Cr, and BiSel:Cr single crystals were grown by the vertical Bridgman technique using the ingots synthesized from the high-purity (99.9999%) elements antimony, bismuth, sulphur, selenium, iodine and chromium. The grown single crystals crystallized in the or thorhombic structure and had an indirect energy-band; structure. The t emperature dependence of the optical energy gap was well fitted by the Varshni equation. When chromium was doped into the single crystals, i mpurities in the optical absorption peaks appeared, and were attribute d to the electron transitions between the energy levels of Cr2+ ions s ited at the T-d symmetry point in the host lattice.