Spectra and decay kinetics of radiative recombination in CdS microcrystals

Low-temperature luminescence spectra of CdS microcrystals grown in a transparent silicate glass matrix have been studied. The microcrystal size could be varied during growth from a new tens to a few thousands of an angstrom. The spectra of fairly large microcrystals (≈400A) reveal lines originating from free and bound exciton annihilation. The exciton luminescence intensity drops with decreasing microcrystal size, the emission spectra of microcrystals of size less than a few hundred angstrom being dominated by transitions involving impurities and lattice defects. Effects associated with surface band bending in large microcrystals have been revealed and studied. A study has been made of the position and kinetics of the interimpurity luminescence bands as a function of microcrystal size. A theory has been developed to describe the energy spectrum of shallow donor levels and of the interimpurity recombination kinetics in semiconductor microcrystals.