Metalorganic Chemical Vapor Deposition of AlScN Thin Films and AlScN/AlN/GaN Heterostructures

Abstract: AlScN thin films were grown via metalorganic chemical vapor deposition (MOCVD), showing controllable incorporation of scandium (Sc) into the AlN lattices. Systematic variation of growth parameters demonstrated an obvious influence on Sc incorporation, with X-ray photoelectron spectroscopy (XPS) analysis indicating Sc composition up to $\sim$13\% when (MCp)$_2$ScCl was used as the precursor. AlScN/AlN/GaN heterostructures grown on GaN templates exhibited the formation of a two-dimensional electron gas (2DEG) channel at the AlScN/AlN--GaN interface, confirming their potential use in high electron mobility transistor (HEMT) device technologies. Variation in AlScN/AlN barrier thickness within the heterostructures showed that thicker barriers yield higher sheet charge densities from both Hall and capacitance-voltage (C--V) measurements. With an AlScN/AlN barrier thickness of $\sim$30~nm, a sheet charge density of $5.22\times10^{12}$~cm$^{-2}$ was extracted from C--V. High-resolution scanning transmission electron microscopy (S/TEM) further confirmed Sc incorporation and revealed the wurtzite crystalline structure of the films and heterostructures. These results establish MOCVD growth of AlScN as a promising and compatible material for advancing III-nitride heterostructures in high-performance electronics and potentially ferroelectrics.