AC and DC Quantum Hall Measurements in GaAs-Based Devices at Temperatures Up To 4.2 K

In this paper, we describe ac and dc quantum Hall effect measurements at temperatures above 1.5 K, which is beyond the commonly used value for high precision measurements of the quantum Hall resistance (QHR). It is shown that GaAs devices with high electron density of about 5 × 10
¹¹
cm
²
can be used as reliable dc resistance quantum standards with quantization of R
_H
(2) value with accuracy within a few parts in 10
⁹
even at temperatures up to 4.2 K. The devices have exhibited well-developed quantum Hall plateaus in the ac regime too, again at temperatures up to 4.2 K. The measurement system consists of a self-made cryogenic probe with TO-8 type socket together with coaxial wiring and a digitally assisted bridge suitable for ac quantum Hall effect measurements. The experiments were performed with devices placed in new double-shielded TO-8 holders. Our investigations and the evaluation of the measurement system are dedicated for the future realization of the quantum impedance standard based on ac QHR.