Search

© 2002 The American Physical Society. We thank L. C. Andreani and B. Méndez for the careful reading of the manuscript and G. Guizzetti for enlightening discussions. V.B. was partially supported by MURST (Project ‘Giovani Ricercato’). Work at Madrid was supported by DGI-MCyT (Project No. MAT2000-0734) and CAM (Project No. 07N/0075/20019., We studied the optical properties of ordered and intentionally disordered GaAs-AlxGa1-xAs superlattices, with and without dimer-type correlations in the disorder, by means of spectroscopic ellipsometry. The electronic structure of the superlattices has been calculated and compared with the experiments. The optical transitions in ordered, correlated, and uncorrelated disordered superlattices show specific features that we relate to their different electronic structures., MURST, DGI-MCyT, CAM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1999 The American Physical Society. Work in Italy has been supported by the INFM Network “Fisica e Tecnologia dei Semiconduttori III-V” and in Madrid by the CAM under Project No. 07N/0034/1998. E. D. and F. D.-A. thank A. Sánchez for collaboration on these topics during these years., We study the electronic properties of GaAs-AlGaAs superlattices with intentional correlated disorder by means of photoluminescence and vertical de resistance. The results are compared to those obtained in ordered and uncorrelated disordered superlattices. We report the first experimental evidence that spatial correlations inhibit localization of states in disordered low-dimensional systems, as our previous theoretical calculations suggested, in contrast to the earlier belief that all eigenstates are localized., CAM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2001 The American Physical Society. We are grateful to J. C. Flores, K. Fujiwara, G. Guizzetti, M. Hilke, C. Kanyinda-Malu, A. Stella, and D. Tsui for their enlightening discussions. Work in Italy has been supported by the INFM Network ‘‘Fisica e Tecnologia dei Semiconduttori III-V’’ and in Madrid by DGES under Project MAT2000-0734., We report a systematic study of several GaAs-AlxGa1-xAs semiconductor superlattices grown by molecular-beam epitaxy specifically designed to explore the existence of extended states in random dimer superlattices. We have confirmed our previous results [V. Bellani et al., Phys. Rev. Lett. 82, 2159 (1999)] with much additional evidence that allows us to lay claim to a clear-cut experimental verification of the presence of extended states in random dimer superlattices due to the short-range correlations (dimers) that inhibit the localization effects of the disorder., DGES, INFM Network ‘‘Fisica e Tecnologia dei Semiconduttori III-V’’, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub