Formation of extended states in disordered two-dimensional In0.4Ga0.6As/GaAs(311)B quantum dot superlattices

Formation of extended states or minibands in two-dimensional (2D) In0.4Ga0. 6As/GaAs(311)B quantum dot superlattices (QDSLs) is directly demonstrated i n time-resolved photoluminescence measurements. At a low excitation density of 1 W/cm(2), photoluminescence transients with similar to 15 ps rise time and similar to 25 ps decay time are observed. Both rise and decay times ar e found to increase with increasing excitation density. The excitons in 2D QDSLs exhibit different relaxation and recombination behaviors as compared to those in quantum wells and quantum dots. A physical model treating 2D QD SLs as disordered systems containing localized and extended states can succ essfully interpret all of the experimental observations. (C) 2000 American Institute of Physics. [S0021-8979(00)03313- 2].