Optical properties of submonolayer CdSe-(Zn,Mg)(S,Se) structures

The optical properties of structures with submonolayer inclusions of CdSe in a Zn(S,Se) matrix are studied. The submonolayer coating consists of a group of nanosized (40 Angstrom) islands with a height of one monolayer. The exciton oscillator strength of multiple submonolayer CdSe-ZnSSe structures is substantially increased compared to the case of a uniform quantum well of comparable thickness and composition. In submonolayer structures lasing takes place immediately next to the energy of the ground state of the heavy exciton, in contrast with ordinary quantum wells of ZnCdSe, where it is strongly shifted to longer wavelengths by the energy of a single optical phonon. This effect results from the removal of the momentum selection rules during radiative recombination of excitons in submonolayer structures. (C) 1997 American Institute of Physics.