Photoconductivity of Pure Cadmium Sulfide Single Crystal near the Band Edge

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 P 1 (507.5 mµ), P 3 (517 mµ) and P 5 (532 mµ) appear in the crystal containing sulfur vacancies and that P 2 (513.5 mµ) and P 4 (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 P 1 . From the results, the possible electronic transitions are discussed.