Third International Conference on Optics of Excitons in Confined

Le Journal de Physique IV 03 (1993) C5-291-C5-294
DOI: 10.1051/jp4:1993558

Effect of thermal diffusion on the excitonic reflectivity spectra of InGaAs/GaAs quantum wells

W.P. GILLIN¹, H. PEYRE², J. CAMASSEL², K.P. HOMEWOOD¹, I.V. BRADLEY¹ and R. GREY<sup>3

1</sup>  Department of Electronic and Electrical Engineering University of Surrey, Guildford, Surrey GU2 5XH, U.K.
²  Groupe d'Etudes des Semiconducteurs, CNRS, CC074, Université Montpellier II, 34095 Montpellier cedex 5, France
³  Department of Electronic and Electrical Engineering University of Sheffield, Mappin Street, Sheffield S13JD, U.K.

Abstract
We have investigated the effect of intermixing on the excitonic reflectivity spectra of a 100 Å thick InGaAs/GaAs quantum well (QW). We could resolve both the E_l - H_l and E₂ - H₂ excitonic features, up to L_D = 80 Å. We show that both energy shifts agree well with a simple mode1 which assumes a Fick's law diffision, with a diffusion coefficient that is independent of the concentration of the cationic species. Next, considering the change (improvement) in signal to : noise ratio versus thermal annealing, we suggest that, in our samples, we not only get a broadening of the quantum well as the diffision proceeds but, also, a diffision of the lattice constituents in the plane of the well. This in-plane diffision smoothes the interfaces and reduces the monolayer well width fluctuations.

© EDP Sciences 1993