Effect of Additional Irradiation Induced Scattering Centres on the Quantum Hall Plateau Widths in GaAs-Al_xGa_1−xAs Heterostructures

Abstract

The presence of random scattering centres in a two-dimensional electron gas (2DEG) is essential for the occurrence and the widths of the quantum Hall effect (QHE) plateaus within the localization model [1]. Scaling theory indicates that within a infinite two-dimensional system all states are localized by quantum coherence effects for any degree of disorder [2]. Concerning the QHE the localization model describes the effect of disorder on the localization of Landau states. Within this model the QHE plateau width should be proportional to the number of electrons in localized states above the upper mobility edge of the highest filled Landau band plus those below the lower mobility edge in the next higher band in energy. In a recent paper we studied the effect of low temperature proton irradiation on the resistivity ρ, mobility µ, carrier concentration n and QHE structures of GaAs-A1_xGa_1−xAs heterostructures [3]. As a continuation of this work we present a systematic investigation of these quantities on irradiation induced disorder with additional emphasis on the comparison of different samples. To this purpose GaAs-Al_xGa_1−xAs heterostructures were successively irradiated with 6 MeV protons and the longitudinal and transversal resistivities ρ _xx and ρ _xy were measured in magnetic fields after each dose.