Description:

Title: Beyond the Hall effect: Novel characterization techniques for 21st century electronic materials

Speaker: Matthew Grayson, Electrical Engineering and Computer Science, Northwestern University

Abstract: The standard method for characterizing mobility and density in semiconductors stems from the fundamental magnetotransport discoveries of Edwin Hall (1879) adapted by van der Pauw (1956). However, modern electronic materials – including narrow gap semiconductor superlattices for infrared detectors and lasers, transverse thermoelectric materials, as well as parallel conducting layers – can have multiple species of carriers with anisotropic conductivities and non-uniform doping, requiring more sophisticated magnetotransport methods. Recent breakthroughs allow us to fully characterize the various parameters in such materials. For example, a comparison of +B and –B longitudinal magnetoresistances can be used to quantify the doping gradient in a sample [1]. Fourier-transform mobility spectral analysis can deduce an entire spectrum of conducting electrons and holes within a wide mobility range μ = 10^2 – 10^6 cm^2/Vs [2]. Careful magnetotransport analysis can separately extract the mobility and carrier density of a parallel conducting layer in a quantum Hall effect sample [3] or the anisotropic conductivity tensor of a superlattice [4]. In this talk, I will summarize these breakthroughs in characterization methods that overcome a variety of challenges posed by modern electronic materials.

[1] W. Zhou, MG, et al, Phys. Rev. Lett. 115, 186804 (2015).
[2] B. Cui, Y. Tang, MG, Proc. SPIE 9370, 937030 (2015).
[3] MG and F. Fisher, J. Appl. Phys. 98, 013709 (2005).
[4] Y. Tang, MG, Proc. SPIE 9730, 97300L (2015).

Host: Garg

Speaker Schedule

Keywords: Physics, Astronomy, colloquium