BAND-EDGE ABSORPTION AND LUMINESCENCE OF NONSPHERICAL NANOMETER-SIZE CRYSTALS

The effect of nonspherical shape on the optical properties of semicond uctor microcrystals with a degenerate valence band has been theoretica lly studied. The asymmetry of microcrystals leads to a splitting of th e fourfold-degenerate ground hole state into two twofold-degenerate on es. The value of this splitting is proportional to the deviation from sphericity and inversely proportional to the square of the microcrysta l size, and is the function of the ratio of light- to heavy-hole effec tive masses (beta). This splitting could lead to the formation of long -lived electron-hole pairs in the prolate microcrystals of semiconduct ors with small beta and in the oblate ones with beta > 0.14.