Superlattices and Microstructures, Vol. 22, No. 3, 1997 Well-width dependence of interface roughness scattering in GaAs/Ga 1−x Al x As quantum wells N. Balkan University of Essex, Department of Physics, Colchester, UK R. Gupta University of Hull, Department of Electronic Engineering, Hull, UK M. Cankurtaran, H. C ¸elik, A. Bayrakli, E. Tiras Hacettepe University, Department of Physics, Beytepe, Ankara, Turkey M. C ¸ . Arikan Department of Physics, University of Istanbul, 34459 Vezneciler, Istanbul and, TUBITAK, Research Institute for Basic Sciences, 41470 Gebze, Kocaeli, Turkey (Received 25 March 1997) Well-width dependence of quantum and transport mobilities of electrons in GaAs/GaAlAs multiple quantum wells is studied for wells with widths ranging between 50 ˚ A and 145 ˚ A. Experimental results are obtained from the amplitude analysis of the Shubnikov–de Haas (SdH) oscillations and from conventional Hall measurements at temperatures between T = 15 K and 4.2 K. A novel technique is employed to estimate, theoretically, the interface roughness parameters from electron quantum and transport lifetimes. The modelling is carried out for a range of layer fluctuations, width () and lateral size (), as to obtain the best fit to the experimental results for individual samples. Our results indicate that the interface roughness scattering limits equal both quantum and transport mobilities at low temperatures, and that the nature of scattering by interface roughness (small or large angle) depends not only on the size and the width of the fluctuations but also on the distribution of these fluctuations within the samples. Therefore, unlike the predictions of the existing theoretical models, which assume constant values of  and  for all well widths, the well-width dependence of interface roughness scattering cannot be verified experimentally. c  1997 Academic Press Limited 1. Introduction Interface roughness (IFR) in layered structures can be in the form of well-width fluctuations or alloy fluctuations, both leading to the perturbation of the electron confinement energy [1–3]. The presence of the IFR in optical devices can lead to some undesirable effects such as the splitting or broadening of excitonic spectra. The effect is more prominent in narrower wells where a few monolayer fluctuations in the well-width 0749–6036/97/070263 + 09 $25.00/0 sm960458 c  1997 Academic Press Limited