INTERACTION OF FREE-CARRIERS WITH LOCALIZED EXCITONS IN QUANTUM-WELLS

Scattering of free carriers by localized excitons in quantum-well stru ctures is studied theoretically. The processes under consideration are free-carrier-induced transitions of the excitons from localized into free states. It is shown that the exciton delocalization probability i s mainly contributed by exchange processes in which the initial electr on finds itself bound in the exciton and the excitonic electron is eje cted. The contribution of the direct processes is small even for the e lectron and hole in-plane effective masses differing by a factor of 2. For the electron concentration n = 10(9) cm(-2) and temperatures T > 5 K, the delocalization time tau < 1 ns and it decreases by an order o f magnitude with T increasing from 5 K to 8 K. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.