Spectral and time dependences of the radiation emitted by cadmium sulfide crystals

A study was made of time and spectral-time characteristics of the radiation emitted from pure and doped cadmium sulfide subjected to high rates of excitation (10²⁷ – 10²⁸ cm^–3·sec^–1) at 300 °K. The radiative transition times were determined for various recombination channels: τ_ex = (11–12)×10^–9 sec for the exciton mechanism accompanied by the emission of one or two phonons; τ_ib = 6×10^–9 sec for the interband mechanism (when the nonequilibrium carrier density was Δn = 1×10¹⁸ cm^–3); τ_imp = (1–3)×10^–9 sec for the mechanism involving shallow impurities. The interband radiative recombination coefficient B_ib = 1.55×10^–10 cm³/sec (Δn ~10¹⁸ cm^–3), the critical density for the Mott transition n_cr = 6.5 ×10¹⁷ cm^–3, and the coefficient representing the binding of carriers into excitons γ_ex ≈ 10^–8 cm³/sec were determined.