Strain-induced indirect-to-direct bandgap transition in an np-type LaAlO3/SrTiO3(110) superlattice

Using first-principles calculations, we studied the influence of in-plane strain on the electronic properties of the polar LaAlO3/SrTiO3 (LAO/STO)(110) superlattice. We propose that alternate positively (n-type) and negatively (p-type) charged interfaces can be introduced along the [110] direction,...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2019, Vol.21 (13), p.7075-7082
Main Authors: Wang, L, Pan, W, Hu, W X, Sun, D Y
Format: Article
Language:English
Subjects:
Electron gas
Electronic properties
Energy gap
First principles
Plane strain
Stoichiometry
Strontium titanates
Superlattices
Thickness
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Summary:Using first-principles calculations, we studied the influence of in-plane strain on the electronic properties of the polar LaAlO3/SrTiO3 (LAO/STO)(110) superlattice. We propose that alternate positively (n-type) and negatively (p-type) charged interfaces can be introduced along the [110] direction, without changing the stoichiometry of the system, if the np-type LAO/STO(001) superlattice is constructed in a 45° stepped pattern. We find that when the LAO–STO layer thickness is larger than the critical thickness of the insulator–metal transition, a quasi-two dimensional hole gas and an anisotropic quasi-two dimensional electron gas are formed at alternate interfaces. By applying uniaxial in-plane strains, an unexpected indirect-to-direct bandgap transition occurs in the polar LAO/STO(110) superlattices. The strain-induced changes in the O-2p orbitals near the p-type interface modify the dispersion of valence-band edges, leading to the transition.
ISSN:1463-9076
1463-9084
DOI:10.1039/c8cp07761d