(ZN,CD)SE ZNSE QUANTUM-WELL LASERS - EXCITONIC GAIN IN AN INHOMOGENEOUSLY BROADENED QUASI-2-DIMENSIONAL SYSTEM/

Optical properties of a strongly excitonic quasi-two-dimensional syste m in a wide-band-gap II-VI semiconductor heterostructure are investiga ted in terms of the relationship between absorption and stimulated emi ssion. In particular, the optical gain in (Zn,Cd)Se/ZnSe quantum-well lasers is demonstrated to be of excitonic nature over a wide range of temperatures, and to occur at electron-hole pair densities below the e xciton-electron hole plasma transition. Both steady-state and transien t (picosecond and femtosecond) spectroscopic techniques have been appl ied to detail exciton kinetics within the n = 1 heavy-hole exciton res onance. A phenomenological model of optical gain is proposed; originat ing from an inhomogeneously broadened exciton resonance and including the effects of exciton-phonon interaction.