Origin and distribution of charge carriers in LaAlO3-SrTiO3 oxide heterostructures in the high carrier density limit, Sumanta Mukherjee, Banabir Pal, Debraj Choudhury, Indranil Sarkar, Wolfgang Drube, Mihaela Gorgoi, Olof Karis, H. Takagi, Jobu Matsuno, and D. D. Sarma,
Phys. Rev. B 93, 245124, 2016.
Using hard x-ray photoelectron spectroscopy with variable photon energy (2-8 keV),
we address the distribution of charge carriers in the prototypical LaAlO3 (LAO) and SrTiO3 (STO) oxide heterostructures
with high carrier densities (1017 cm-2). Our results demonstrate the presence of two distinct charge distributions in
this system: one tied to the interface with a ∼ 1-nm width and ∼ 2–5×1014 – cm-2 carrier concentration, while
the other appears distributed nearly homogeneously through the bulk of STO corresponding to a much larger carrier
contribution. Our results also establish bimodal oxygen vacancies, namely on top of LAO and throughout STO,
quantitatively establishing these as the origin of the observed bimodal depth distribution of charge carriers in
these highly doped sample.
|