Current carrier lifetime in doping superlattice crystals

摘要

It is shown, that the lifetime of nonequilibrium current carriers in the luminescence process in doping superlattice structures changes in a wide range with increasing the excitation level of the crystal. Two effects are important, i.e., (1) low-dimensional character of the carrier distribution and (b) change in the overlap of electron and hole wave functions. At low excitation, non-radiative recombination can play principal cause in the stabilization of the effective lifetime of current carriers. At high excitation, the effective lifetime of current carriers approaches the value in the bulk crystal. The major attention was given to the compensated GaAs doping superlattices with i-layers (n-i-p-i crystals) and to the structures with no i-layers (n-p-n-p structures). The layer thickness of n-, p-, and i-type were 20, 40, or 60 nm and the concentrations of the dopants Te and Zn made up to 10~(18) cm~(-3). Photoluminescence spectra and the decay time of the spontaneous emission intensity in the superlattices were measured at the temperature interval from 11 to 300 K. The influence of α-particle irradiation and thermal annealing on the luminescence spectra and the carrier lifetime was also investigated.