LASING AND DYNAMICS OF PHOTOEXCITED CARRIERS IN GRADED-INDEX SEPARATE-CONFINEMENT ZN1-XCDXSE SINGLE QUANTUM-WELLS

In this work we investigated the optical properties and lasing in grad ed-index separate confinement Zn1-xCdxSe/ZnSe heterostructures on In1- xGaxAs (1 0 0) substrate. The carrier dynamics in the confining graded barriers and the single quantum well are investigated by using time-r esolved photoluminescence measurements. Our measurements show the fill ing of quantum well states and depopulation of barrier states in about approximate to 25 ps. Moreover, we observed the reduction of the deca y time of the photoluminescence as the excitation intensity was varied from below to above the threshold for lasing. Lasing threshold in the se structures was found to be reduced by about one order of magnitude with respect to samples without graded-index profile. The threshold fo r lasing was in the range from approximate to 1 to 145 kW/cm(2) when t he sample temperature was varied from 10 to 300 K. In short cavities, at temperatures higher than 150 K a transition from the first to the s econd quantized state was observed. (C) 1998 Elsevier Science B.V. All rights reserved.