Ground state exciton lasing in CdSe submonolayers inserted in a ZnSe matrix

摘要

We study optical properties of ZnMgSSehyphen;ZnCdSe structures with CdSe submonolayers inserted in a ZnSe matrix. Remarkably high exciton oscillator strength is found in ultrashorthyphen;period submonolayer CdSehyphen;ZnSe superlattices, as compared to ZnCdSe quantum wells of comparable average width and Cd composition. In conventional ZnCdSe quantum wells the lasing occurs at energies sim;30 meV below the free heavyhyphen;hole exciton transition revealed in photoluminescence and in optical reflectance spectra. In the CdSe submonolayer superlattices lasing occurs at energies in the very vicinity of the heavy hole exciton resonance, directly in the region of stronglyhyphen;enhanced excitonhyphen;induced modulation of the reflectance spectrum, and, consequently, refractive index change. We attribute the effects observed to exciton localization by potential fluctuations caused by nanoscale CdSe islands formed during submonolayer deposition. copy;1996 American Institute of Physics.