Excitonic relaxation channels in double quantum wells

The purpose of this paper is to give a theoretical interpretation of the experimental results of Goede et al. (Superlatt. Microstruct. 12 363 (1992)) describing the relaxation of heavy-hole excitons in asymmetric double quantum well systems based on the semimagnetic CdTe-CdMnTe system. In order to explain certain spectroscopic data, Goede et al. had to invoke excitonic tunnelling between the wells for systems with narrow (25 AA) inner barriers. In this work it is shown that the experimental results imply tunnelling via a 'crossed' excitonic state with the electron and hole localized in different wells. The experimental observations are interpreted in terms of a model involving phonon scattering and calculations of intersubband relaxation rates via confined phonon modes are shown to be in agreement with experimental observations.