Selection criteria for AlGaAs-GaAs heterostructures in view of their use as a quantum Hall resistance standard

Abstract

The growth of GaAs, AlGaAs, and selectively doped AlGaAs/GaAs heterostructures by metalorganic vapor phase epitaxy using tertiarybutylarsineThe effects of several practical properties of GaAs-AIGaAs heterostructures on the accuracy of a quantum-Hall resistance standard at a level of 1:10 8 are discussed. Conduction through a parallel layer, metallic current contacts, homogeneity of the electron density, sample size, and mobility are addressed. Measurements are presented concerning the infiuences of sample size and mobility. As regards mobility, the slope of the Hall plateau, longitudinal resistance, and critical current have been investigated. Recommendations are given on sample geometry and mobility. Feasible measurement methods are presented to check the absence of a parallel conducting layer and the quality of the contacts. 3487 J.

The quantum Hall effect as an electrical resistance standard

“…where ξ is the localization length and w the sample width. Besides the direct determination of the fundamental length scale ξ as suggested from equation (32), the linear dependence of T eff on the current I was experimentally confirmed [104]. Therefore, electron heating effects may play a role and have to be taken into account in precision measurements irrespective of the further possibility of QHE breakdown (see section 5.3).…”

“…This elliptic profile gives a satisfactory approximation of real systems. Experimentally, the width of a Landau subband was found to be well approximated by [32]…”

Phase diagram for the quantum Hall effect in a high-mobility AlGaN/GaN heterostructure

“…A possible explanation is therefore that the low mobility regions of the sample are only just above this threshold; this is supported by the lack of zero-resistance minima in a sample with µ = 4 200 cm 2 Vs −1 [8]. (For comparison, the lowest resistivity in the ν = 4 SdH minimum of GaAs-AlGaAs 2DEGs has been shown to rise rapidly for mobilities below ∼100 000 cm 2 Vs −1 [9].) In order to plot out the phase diagram for the critical breakdown field, we have followed the approach used earlier [1,2] and measured the width of the minima, 2B c (ν, T ), at a resistivity value which is a fixed fraction of the zero-field value.…”

Quantum Hall devices for the primary resistance standard based on the GaAs/AlxGa1−x As heterostructure

“…The GaAs/Al x Ga 1−x As heterostructure was grown on a GaAs substrate by molecular beam epitaxy with the designed structure, 12 as described in the previous work. 11 The central working magnetic field (B 2c ) of the filling factor i = 2 QH resistance plateau was designed to be above 9 T by adjusting the carrier doping concentration.…”