Spectroscopic evidence for the excitonic lasing mechanism in ultraviolet ZnS/ZnCdS multiple quantum well lasers

We demonstrate optically pumped lasing at room temperature from ZnS/ZnCdS quantum-well structures grown on (100) GaP substrates by molecular beam epitaxy. In the structures with the lowest Cd composition, optically pumped lasing at wavelengths as low as 333 nm (at 8 K) is observed. We present spectroscopic evidence which suggests that the stimulated emission involves states in the low-energy tail of an inhomogeneously broadened excitonic resonance. While lasing is excitonic at low thresholds, a transition to an electron-hole plasma mechanism may occur if the pump power approaches 100 kW cm-2. © 1996 American Institute of Physics.