Behavior of the contacts of quantum Hall effect devices at high currents

Abstract

This paper reports on an experimental study of the contact resistance of Hall bars in the Quantum Hall Effect regime while increasing the current through the sample. These measurements involve also the longitudinal resistance and they have been always performed before the breakdown of the Quantum Hall Effect. Our investigations are restricted to the i = 2 plateau which is used in all metrological measurements of the von Klitzing constant R K . A particular care has been taken concerning the configuration of the measurement. Four configurations were used for each Hall bar by reversing the current and the magnetic field polarities. Several samples with different width have been studied and we observed that the critical current for the contact resistance increases with the width of the Hall bar as previously observed for the critical current of the longitudinal resistance. The critical currents exhibit either a linear or a sublinear increase. All our observations are interpreted in the current understanding of the Quantum hall effect brekdown. Our analysis suggests that a heated region appears at the current contact, develops and then extends in the whole sample while increasing the current. Consequently, we propose to use the contact resistance as an electronic thermometer for the Hall fluid.

Quantum Hall resistance standards from graphene grown by chemical vapour deposition on silicon carbide

“…In GaAs-QHRS supplied with high currents, several experiments based on the measurement of a linear dependence of the breakdown current of the QHE as a function of the Hall bar width, have strongly supported a homogeneous distribution of the current [36]. On the other hand, sub-linear behaviors were also observed, generally in higher carrier-mobility samples [37,38]. It turns out that the current distribution remains difficult to model because it is dependent on the microscopic details of the two-dimensional electron gas, notably of the length scale of inhomogeneities [34,36].…”

Observation of finite excess noise in the voltage-biased quantum Hall regime as a precursor for breakdown

“…The excess noise prior to the breakdown of the QHE behaves in a way closely related to the prebreakdown of the QHE. 21,33,44 Figure 7(a) shows G(V sd ) and S(V sd ) as a function of the normalized source-drain bias voltage (V sd /V BD ) obtained around the ν = 2 QHE state. Data obtained at B = 4.2, 4.0, and 3.8 T are plotted as circles, triangles, and squares, respectively.…”

“…Second, unexpectedly, we observed finite excess noise prior to the QHE breakdown at a finite V sd that is smaller than the onset voltage of the QHE breakdown (a V sd region that we define as a precursor regime), indicating the presence of finite dissipation in the nonequilibrium QHE states. The excess noise behaves in a way closely related to the prebreakdown of the QHE 21,33,44 . Thus, the noise measurement may give us profound information about onset of the breakdown of the QHE.…”

Phase Space for the Breakdown of the Quantum Hall Effect in Epitaxial Graphene

“…3. It should be noted that the values are significantly higher for the 5µm Hall bars and there is some evidence that quantum Hall breakdown current densities are larger for smaller Hall bar widths [2,24] The most widely accepted theory for the QHE breakdown is the bootstrap electron heating model proposed by Komiyama and Kawaguchi [12] in which the quantum Hall state becomes thermally unstable above a critical Hall electric field where the rate of change of electronphonon energy loss rate becomes less than the rate of increase of input power. This predicts a critical breakdown electric field of…”