Dynamics of Excitons in a CdSe-ZnSe Multiple Quantum Well

Abstract

The optical spectrum of II-VI quantum wells (QWs) is, in general, dominated by inhomogeneous broadening, which is caused by random fluctuations of QW layer thickness. In these QWs, hot carriers have not only kinetic energy but also potential energy which varies following the in-plane bandgap fluctuations. Apart from hot-exciton formation and relaxation as in the intrinsic QW, hot carrier relaxation in these QWs also includes the localisation of excitons and the migration of localised excitons between localisation sites. In this paper, we present a study of the exciton relaxation in a 100-period 10Å CdSe-50Å ZnSe multiple quantum well by using time-resolved photoluminescence spectroscopy. The sample has a ±1 monolayer fluctuation in QW thickness. The experimental setup¹ includes a frequency-doubled modelocked Ti: Sapphire laser, a liquid helium cooled cryostat, and a time-resolved luminescence detection system using the up-conversion technique. The overall temporal resolution was about 300 fs and the spectral resolution was 18 meV.