Giant polarization charge density at ScN/GaN interfaces*

GaN is a wurtzite semiconductor that exhibits a large spontaneous polarization, while ScN is a semiconducting nitride that takes the nonpolar rocksalt crystal structure. Due to small lattice mismatch between ScN and GaN, it is possible to create a polar-nonpolar interface between the two materials.

Using density functional theory and the Berry-phase method, we examine the formal polarization of rocksalt ScN along the [111] direction, finding a polarization discontinuity of -1.358 Cm^-2. We confirm this finding with explicit ScN/GaN supercell calculations. The polarization discontinuity causes a high-density electron gas to form on the N-polar GaN/ScN interface, and a hole gas to form on the Ga-polar interface, with carrier concentrations up to 8.5 x 10¹⁴ cm^-2. The large polarization difference and low lattice mismatch make ScN a promising material for integration with III-nitride electronic and optoelectronic devices.