Nitrides Seminar - Christian Zollner, Graduate Student Researcher
10/23/2019 12PM ESB 1001
ScN is a semiconducting nitride that has the rocksalt crystal structure and is almost lattice matched to GaN. AlScN alloys have attracted attention due to large piezoelectric coefficients and the potential for ferroelectricity. We have recently proposed that ScN/GaN interfaces exhibit unique polarization properties. GaN is polar with a large spontaneous polarization, while ScN is centrosymmetric and has a non-polar space group. We therefore predict a very large spontaneous polarization discontinuity at the interface.This is indeed borne out by explicit simulations.
Using density functional theory, we have examined the polarization properties of rocksalt ScN along the  direction.We have also studied a ScN/GaN superlattice, finding a polarization discontinuity at the ScN/GaN interface of -1.388 Cm-2. As a result, a high-density electron gas can form on the N-polar GaN/ScN interface, and a high-density hole gas on the Ga-polar interface, with carrier concentrations up to 8.7 x 1014 cm-2. The large polarization difference and small strain make ScN a promising material for polarization-enhanced tunnel junctions in III-nitride devices.
This work was supported by the Air Force Office of Scientific Research.