ELSEVIER Surface Science 361/362 (1996) 328-332 surfaco soionce Two-dimensional electrons in a lateral magnetic superlattice H.A. Carmona *, A. Nogaret ,, A.K. Geim a, P.C. Main a'*, T.J. Foster ~, M. Henini ~, S.P. Beaumont b, H. McLelland b, M.G. Blamjre c • Department of Physics, University of Notttnghara, Nottingham NG7 2RD, UK b Department of Electronics and Electrical Engineering, University o f Glasgow, Glasgow GI2 8QQ, UK *Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CD2 3QZ, UK ' Received 21 June 1995; accepted for pubfication 30 August 1995 Abstract We have measured the msgnetoresistance measurements of a 2D electron gas subjected to a periodic magnetic field created by the presence of type 11 superconducting stripes on the surface of the heterostructure. We observe oscillatory behaviour due to a commensurability effect between the cyclotron radius and the period of the magnetic field. The results can be understood in terms of a simple semi-cla~cal theory. Keywords: Gallium arsenide; Semiconducting filma; Semiconductor-superconductor interfacesi Superconductor-semiconductor het- erostructures 1. Introduction There have been several recent investigations of the motion of electrons in a two-dimensional electron gas (2DEG) subjected to an inhomogen- eous magnetic field created by patterned supercon- ductors on the surface of the heterostructure. For example, the contribution of a single vortex to the quantum conductivity of a mesoscopic device, and the motion of ballistic electrons in a random magnetic field have been reported F1]. In this work, a periodic array of type 1I superconducting stripes is patterned on top of a heterojunction to create a periodic magnetic field. It has been pre- dicted [2] that the electron mobility undergoes resonant enhancements whenever the cyclotron *Corresponding author. Fax: +44 115 9515180, e-mail: ppepcm@plm 1.nott.ac.uk. diameter at the Fermi level is commensurate with the period of the magnetic potential within a constant phase factor. This effect can be under- stood in a semi-classical picture [3] analogous to the guiding-centre drift resonance in the case of periodic electric potentials [4]. The effects of a modulated magnetic field acting on a 2DEG have been reported recently by two groups [5,6]. 2. Experimental The structure used in the experiments is shown schematically in Fig. la. A high-mobility 2DEG was formed in a standard GaAs/(A1Ga)As hetero- junction 300nm from the sample surface. The electron density was ~ 1.5 x 10is m -2 and the elas- tic mean free path ~ 10/an. A metallic gate of thickness 150nm was deposited on the surface 0039-6028/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved PH S0039-6028 (96) 00414-1