Extracting Quantitative Band-edge Profiles from Buried Heterojunctions from Hard X-ray Photoelectron Spectra

Semiconductor based devices are of broad, general importance, not only in electronics, but also in energy technology. In such devices, internal electric fields dictate the flow of charge that occurs both laterally and vertically. The associated potential profiles can be approximated from electronic transport data, and also calculated via Poisson-Schrodinger modeling, provided the properties of the constituent materials and interface structures are sufficiently well understood. These approaches work well for heterostructures involving, for instance, III-V semiconductors. However, when oxides are involved, such methods become unreliable because of poorly understood defects that can be present. There is, therefore, a critical need for new methods to enable the direct, experimental determination of band-edge profiles in heterojunctions involving these materials. In this lecture, I will demonstrate that hard x-ray photoelectron spectroscopy (HAXPES), interpreted by means of a newly developed algorithm, constitutes such a method. I will illustrate the power and utility of this approach with examples taken from the realm of epitaxial complex oxides on Group IV semiconductors [1-3] .
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[1] Y. Du, P. V. Sushko, S. R. Spurgeon, M. E. Bowden, J. M. Ablett, T.-L. Lee, N. F. Quackenbush, J. C. Woicik, S. A. Chambers, Phys. Rev. Mater. 2, 094602 (2018).
[2] Z. H. Lim, N. F. Quackenbush, A. Penn, M. Chrysler, M. Bowden, Z. Zhu, J. M. Ablett, T.-L. Lee, J. M. LeBeau, J. C. Woicik, P. V. Sushko, S. A. Chambers, J. H. Ngai, Phys. Rev. Lett. 123, 026805 (2019).
[3] P. V. Sushko and S. A. Chambers, Sci. Rep., submitted (2019).