PHOTOLUMINESCENCE LIFETIMES IN GaAs/Al 0.3 Ga 0.7 As STRUCTURES DESIGNED FOR MICROWAVE AND TERAHERTZ DETECTORS

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 meas ured 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.