Le Journal de Physique IV 03 (1993) C5-171-C5-174
Temperature dependence of exciton-capture at impurities in GaAs/AlxGa(1-x) As quantum wellsC.I. HARRIS1, B. MONEMAR1, P.O. HOLTZ1, H. KALT2, M. SUNDARAM3, J.L. MERZ3 and A.C. GOSSARD3
1 Department of Physics and Measurement Technology, Linköping University, Linköping 581 83, Sweden
2 Fachbereich Physik, University of Kaiserslautern, Germany
3 Center for Studies of Quantised Electronic Structures (QUEST), University of California at Santa Barbara, CA 93016, U.S.A.
In this paper we present an investigation of the exciton capture process in GaAs/Al.3Ga.7As quantum wells using a picosecond time-resolved photoluminescence technique. We demonstrate that there are significant differences in the capture mechanism for narrow quantum wells in comparison to bulk material. In particular the initial capture efficiency is shown to increase with temperature. This behaviour is understood in terms of the role of localisation of the free exciton in the potentials caused by the interface roughness. Higher temperatures destroy this localisation process which otherwise limits the total capture rate for the exciton to the impurity. The effect of localisation on capture is also shown to be stronger for narrower wells. We conclude that the relative weakness of bound exciton recombination in the near bandgap luminescence of doped quantum wells can in part be understood by the reduction of capture efficiency due to localisation.
© EDP Sciences 1993