Large conductance anisotropy in a novel two-dimensional electron system grown on vicinal (111)<i>B</i> GaAs with multiatomic steps

Abstract

A novel selectively doped AlGaAs/GaAs heterojunction was successfully formed on a vicinal (111)B substrate, in which both quasiperiodic and aperiodic multiatomic steps with the average spacings of ∼20 nm are introduced. It is found that the electrical conductance G⊥ of two-dimensional electrons across the steps is far lower than that of G∥ along the steps and the ratio G∥/G⊥ exceeds 100 at 18 K. While G∥ is almost independent of temperature T below ∼70 K, G⊥ increases exponentially with 1/T with the activation energy of ∼5 meV, indicating the presence of potential barriers for the electron motion across the aperiodic steps.