Third International Conference on Optics of Excitons in Confined

Le Journal de Physique IV 03 (1993) C5-225-C5-228
DOI: 10.1051/jp4:1993542

Type II narrow double barrier quantum well structures : Γ-X coupling and interface effects

B. CHASTAINGT¹, G. NEU¹, C. DEPARIS¹, J. MASSIES¹, J. MARTINEZ-PASTOR², M. COLOCCI³ and M. GURIOLI<sup>3

1</sup>  Laboratoire de Physique du Solide et Energie Solaire, Centre National de la Recherche Scientifique, Sophia Antipolis, rue B. Grégory, 06560 Valbonne, France
²  Departament de Physica Aplicada, Universitat de Valencia, 46100 Burjassot, Valencia, Spain
³  European Laboratory for Non Linear Spectroscopy, Department of Physics, University of Florence, Largo Enrico Fermi 2, 50125 Firenze, Italy

Abstract
Photoluminescence (PL), PL excitation and time resolved PL experiments have been performed on Al_0.42Ga_0.58As/AlAs/GaAs symmetric double barrier quantum wells (DBQW) with only one or two AlAs monolayers constituting the intermediate barriers. In agreement with the envelope function predictions we show that such DBQW's undergo a type I - type II transition when the GaAs thickness is reduced below 7 and 5 monolayers for 2 and 1 AlAs molecular planes respectively. In type II configuration the PL decay time is found to be strongly dependent on the energy difference between AlAs X_z - and GaAs Γ - electron confined states and the coupling parameter of the Γ and X_z valleys can be deduced (4.2 meV on average). Similar experiments on DBQW's grown on 2° off (001) vicinal surfaces show that the exciton lifetime remains close to that of nominal samples. Considering also former results obtained in type II GaAs/AlAs superlattices, it is concluded that the Γ-X mixing potential in quantum structures is intrinsically linked to the AlAs/GaAs interface.

© EDP Sciences 1993