Photoluminescence lifetimes in GaAs/Al_0.3Ga_0.7As structures designed for microwave and terahertz detectors

Abstract

This paper presents the photoluminescence spectra and light emission lifetimes in GaAs/Al 0.3 Ga 0.7 As structures designed for microwave and terahertz detectors. The photoluminescence and light emission lifetimes were investigated both before and after etching of the cap-layers, and possible mechanisms of carrier recombination are discussed. The characteristic time of the free exciton emission corresponds to 0.5 ns at a temperature of 3.6 K. The recombination lifetime of the free electron acceptor was measured to be 22-25 ns in GaAs structures and 4-15 ns in AlGaAs structures. The emission lifetime of deep Si level having 170 meV activation energy in AlGaAs layer was found to be equal to 40 ns. The excitonic photoluminescence maxima of n + /n-GaAs and n + /n-Al 0.3 Ga 0.7 As homojunction structures in comparison to n-GaAs and n-Al 0.3 Ga 0.7 As were shifted by approximately 200 ps. This suggested that the drift of free carriers is important in the formation of free excitons in n-GaAs and n-Al 0.3 Ga 0.7 As layers.