Photoconductivity of Pure Cadmium Sulfide Single Crystal near the Band Edge

Abstract

Several peaks of the photoconductivity near the band edge of the cadmium sulfide single crystals are studied. The peaks are due to the exciton and the shallow donors caused by the native defects. The correlation between the peaks and the defects due to the deviation from the stoichiometry of the crystals is investigated. At 300°K it is confirmed that P₁(507.5 mμ), P₃(517 mμ) and P₅(532 mμ) appear in the crystal containing sulfur vacancies and that P₂(513.5 mμ) and P₄(522.5 mμ) are remarkable in the crystal containing cadmium interstitials. The peaks of the exciton photoconductivity, i.e., A, B and C, were observed at 501.5 mμ, 498 mμ and 485.5 mμ at 300°K, respectively. The temperature shift of the band edge is estimated to be 3.00×10⁻⁴ eV/°K from the data of the exciton A, B and C and P₁. From the results, the possible electronic transitions are discussed.