Direct determination of the density of states in two-dimensional systems by magnetocapacitances of biased double barrier structures

Abstract The magnetocapacitive response of a double-barrier structure (DBS), biased beyond resonances, has for the first time been employed as a reliable method to determine the density of states (DOS) of two-dimensional (2D) electrons residing in the accumulation layer on the incident side of the DBS. Model calculations with a Gaussian-like DOS are compared with the experimental C versus B curves, measured at different biases and temperatures. The fitting is not only self-consistent but also remarkably good even in well-defined quantum Hall regimes. It is therefore evident that replacing a conventional gated heterostructure by a biased DBS makes it possible that the influence of the magnetoresistance of “lateral” 2D channel may be eliminated completely in the determination of the DOS, while the possible coexistence of three-dimensional (3D) electrons in the accumulation layer can easily be discriminated by experiments.