CHANGE OF DIMENSIONALITY OF SEMICONDUCTOR SUPERLATTICES INDUCED BY ANINPLANE MAGNETIC-FIELD

We have investigated the Fermi surface of MOVPE-grown coupled In-0.53G a0.47As/InP multiple quantum-wells with delta-doped barriers by angle- resolved Shubnikov-de-Haas measurements in magnetic fields up to 14 T. The shape of the Fermi surface clearly demonstrates the anisotropic 3 D character of the samples. The coupling, originated by the overlap of the electron wave functions of adjacent quantum-wells, should be infl uenced by an in-plane magnetic field due to the reduction of the magne tic length in growth direction (z-direction). For a strongly coupled m ultiple quantum-well, the experimentally determined Fermi surface is w ell described by the Kronig-Penney model. In case of a less coupled sa mple, the Fermi surface can also be described by the Kronig-Penney mod el in case of weak in-plane fields. At higher tilt angles phi (or high er in-plane magnetic fields) deviations from the theoretical curve occ ur. The Fermi surface above these angles exhibits a nearly cylindrical shape, which is expected for a 2D electron system. This is, to our kn owledge, the first experimental proof of a magnetic-held induced 3D-2D transition of a semiconductor superlattice. (C) 1998 Elsevier Science B.V. All rights reserved.