The optical properties of CdS crystal grown by the sublimation method

A cadmium sulfide (CdS) single crystal was grown by the sublimation method without a seed crystal in a two-stage vertical electric furnace. The carrie r concentration and mobility obtained from Hall measurements at room temper ature were 2.90 x 10(16) h cm(-3) and 316 cm(2)/Vs, respectively. The photo luminescence and the photocurrent measurement of the CdS single crystal hav e been performed in the temperature ranging from 20 to 293 K. From the phot oluminescence measurement, the energy of the free exciton Ex(A) and Ex(B) h as been obtained to be 2.5511 and 2.5707 eV, respectively. The variance of the peak position, intensity, and linewidth of the free excitons as a funct ion of the temperature have been investigated by means of the conventional empirical relations and Toyozawa's theory. The crystal field of the CdS and its splitting energy, Delta c(r), have been found to be 19.6 meV. In the p hotocurrent measurement, only the Ex(A) exciton peak has been observed. The energy band gap of the CdS at room temperature was determined to be 2.4749 eV by the photoluminescence and photocurrent measurement. Also, the tempera ture dependence of the energy band gap of the CdS, E-g(T), has been examine d. (C) 2000 Elsevier Science B.V. All rights reserved.