Exciton distribution function and secondary radiation in polar semiconductors

Overview & Synopsis

An explicit non-equilibrium distribution function for excitons in the ground state n = 1 in the case when the fundamental interaction is with acoustical phonons is calculated for polar semiconductors. Using it, a general expression for the secondary radiation cross-section (valid for Raman, hot and thermalized luminescence processes), is obtained. The results are applied to explain the temperature dependence of the 1LO and 2LO luminescence lines half-width in CdS single crystals. The relative contributions of 3LO Raman and luminescence intensities and the variation of the secondary emission spectrum as a function of the exciton life-time are studied. Comparison with experimental results yields quantitative agreement.