Theoretical study of the density of shallow-acceptor impurity states in quantum-size GaAs microcrystals

A theoretical study of the density of states of shallow-acceptor impurities in cylindrically shaped GaAs low-dimensional systems is presented. The acc eptor states are described within a variational scheme in the effective-mas s approximation and using an infinite confinement potential model. The dens ity of impurity states is calculated for a homogeneous distribution of acce ptor impurities within the low-dimensional heterostructure. For dimensions of the system in which the length is much larger than the radius we obtain two well-defined peaks, associated with accepters either at the on-centre p osition or at the edge position in the low-dimensional system. Ln addition, we have observed the appearance in the density of impurity states of an ad ditional peak (with low relative intensity and binding energy) associated w ith impurities located near to the intersection between the cylindrical sur face and the top or bottom end faces of the structure. The general behaviou r we observed in the density of impurity states describes reasonably well t he spectral features present in experimental and theoretical data about acc eptor-related photoluminescence spectra in GaAs microcrystals, cylindrical GaAs quantum-well wires and cylindrically shaped finite-length GaAs heteros tructures.