Nickel Oxide–Based Heterostructures with Large Band Offsets

Description

The authors present research on the electronic transport in heterostructures based on p-type nickel oxide (NiO) with the n-type oxide semiconductors zinc oxide (ZnO) and cadmium oxide (CdO). NiO is a desirable candidate for application in (opto)electronic devices. Because of its small electron affinity, heterojunctions with most n-type oxide semiconductors exhibit conduction and valence band offsets at the heterointerface in excess of 1 eV. ZnO/NiO junctions exhibit a so-called type-II band alignment, making interfacial electron-hole recombination the only process enabling vertical current flow through the structure. These heterojunctions are nevertheless shown to be of practical use in optoelectronic devices, as exemplified here by UV-converting transparent solar cells. These devices, although exhibiting high conversion efficiencies, suffer from two light-activated recombination channels connected to the type-II interface, one of which the authors analyze in more detail here. Furthermore, CdO/NiO contacts are studied-a heterostructure with even larger band offsets, achieving a type-III band alignment which theoretically enables the development of a 2D electronic system consisting of topologically protected states. The authors present experiments demonstrating that CdO/NiO heterostructures indeed hosts a conductive layer absent in both materials when studied separately.

Abstract

International audience

Additional details