Control of carrier lifetimes in PbTe doping superlattices

Abstract

Following subnanosecond pulsed laser excitation, time-resolved photoconductivity has been measured in PbTe doping superlattices in the temperature range 50–200 K. The carrier lifetime changes drastically by about three orders of magnitude during the recombination processes indicating an instantaneous lifetime which varies from a ns time scale up to about 1 μs. The temporal evolution is explained by the initially complete flattening of the built-in superlattice electrostatic potential and its recovery with the decrease in the nonequilibrium carrier concentration. The temperature dependence of the recombination is determined by both the bulk band structure of PbTe and the superlattice potential. The effective lifetime initially increases with temperature due to a decrease in the electron-hole recombination by tunneling, but decreases at higher temperatures where a thermal activation process dominates.