Abstract
Tunnelling spectroscopy between laterally positioned low-dimensional electron systems is investigated. We demonstrate that a reliable highly transparent tunnelling barrier can be fabricated by means of dynamic ploughing with the tip of an atomic force microscope and wet etching into the surface of a GaAs/AlGaAs heterostructure. This barrier allows to perform a tunnelling spectroscopy with dc bias voltages up to 30 mV. Band edge effects due to tunnel coupling were observed for two-dimensional electron gases (2DEGs) separated by such lateral tunnel barrier. Tunneling spectroscopy of a 2DEG and a laterally adjacent electron waveguide enable to monitor the one-dimensional (1D) density of states. Firstly, a lateral dual electron waveguide with 1D subband spacings of more than 5 meV was implemented showing significant features of 1D mode coupling in tunnelling spectroscopy.
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