Abstract

A new method for measuring several devices in a single cool down has been recently designed by the group. It is based on a multiplexing scheme, which allows different two-dimensional (2D) channels to be addressed separately [1]. Using two multiplexers enables an array of devices to be measured, the lines and columns being selected by the multiplexers. This work explores some possibilities offered by this new technique.

First, the multiplexer is used to study one-dimensional (1D) transport in a GaAs/AlGaAs heterostructure. Whereas the quantisation of the 1D conductance G is well described by the theory [2-3], an additional plateau occurring at G=0.7×(2e^2)/h, called the 0.7 anomaly, is not yet fully understood. This work aims at proposing a statistically significant set of data to better understand this phenomenon. In this case, the array of devices addressed by the two multiplexers is composed of split-gates.

The second part of this work focuses on 2D transport (the split-gates are replaced by bar-gates in the array). Using the capacitor model of the 2D channels [4], this work characterises the electron density homogeneity of the measured wafer and the effect of cooling rate on this homogeneity.

[1] H. Al-Taie etal. Applied Physics Letters, 102(243102): 1–4, 2013. [2] R. Landauer. IBM Journal of Research and Development, 1(3): 306, 1957. [3] M. Büttiker. Physical Review B, 41(11): 7906–7909, 1990. [4] C. J. B. Ford. Part III minor option (University of Cambridge), chapter 5.