LIGHT-EMISSION BY SEMICONDUCTOR NANOSTRUCTURES IN DIELECTRIC MEDIUM ON CLOSE TO PLANE INTERFACE

We review several situations in which the emission rate of a nanostruc ture is modified by its environment. We first consider small objects e mbedded in media with different refractive indices. The local electrom agnetic field and the rate of spontaneous emission of the nanostructur e are enhanced or inhibited by the induced dipole charges on the inter face. In quantum wells or nanocrystals embedded in a low dielectric co nstant medium, tile binding energy of excitons is increased. In anisot ropic microcrystals, tile local field is anisotropic and emission of l ight is polarized. We consider especially the case of p(+)-doped porou s silicon in which nanocrystals are elongated. Another interesting sit uation occurs when a dipole is in the vicinity of a dielectric interfa ce. The local field acting on the dipole results from the interference s of incident and reflected beams. Contributions from evanescent waves are important when the dipole is located in the medium of low refract ive index, very close to the surface. The intensity of emission and it s pattern are modified by the vicinity of the dielectric interface. Cl ose to the interface semiconductor/air, the exciton binding energy is increased. In the vicinity of a metallic surface, a nonradiative trans fer to the metal occurs for small distances of the nano-object or quan tum well to the surface and the quantum efficiency varies with the dis tance to the metallic surface. The exciton binding energy of a quantum well is decreased close to a metallic surface.