The Increase of Radiative Lifetime of Free Excitons in Selectively Si-doped GaAs/Al sub(x)Ga sub(1-x)As Heterostructures

The time resolved photoluminescence spectra of selectively Si-doped GaAs/Al sub(x)Ga sub(1-x)As heterostructures have been investigated over a wide temperature range from 3.6 K to 300 K in order to identify possible mechanisms behind the observed increase in radiative lifetime of free excitons. Possible mechanisms of carrier recombination are discussed with emphasis on the unique traits of excitonic photoluminescence. The intensive lines found in the spectra of the heterostructures are associated with the formation and enhancement of free exciton emission in the flat band region of an active i-GaAs layer. We have established that the free exciton radiative lifetime in the heterostructures increases about two times, up to 1.44 ns in comparison with lifetime 0.6 ns of i-GaAs layer without a heterostructure for first sample and up to 0.92 ns from 0.4 ns for second sample at 3.6 K temperature.Original Abstract: Selektyviai Si donorais legiruotu GaAs-Al sub(x)Ga sub(1-x)As heterodariniu fotoliuminescencijos kinetika istirta taikant pavieniu koreliuotu fotonu skaiciavimo metodika. Tyrimai atlikti 3,6 K-300 K temperaturose siekiant nustatyti laisvojo eksitono spinduliuotes trukmiu pailgejimo priezasti. Aptariami galimi kruvininku rekombinacijos mechanizmai, budingi eksitoninei spinduliuotei. Intensyvios linijos, stebetos heterodariniu spektruose, yra susijusios su eksitonines spinduliuotes formavimusi ir sustiprejimu i-GaAs sluoksnyje. Nustatyta, kad laisvojo eksitono gyvavimo trukme heterodariniuose padideja apie du kartus: nuo 0,6 ns gyvavimo trukmes i-GaAs sluoksnyje be heterodarinio iki 1,44 ns vienam bandiniui 3,6 K temperaturoje ir nuo 0,4 ns gyvavimo trukmes iki 0,92 ns kitam bandiniui.