Paper TF-ThP41
Reactive Magnetron Sputtering of Epitaxial Scandium Nitride for High Performance Electronics

Thursday, November 10, 2016, 6:00 pm, Room Hall D

With technological advances in electronics increasing the need for high performance devices (i.e. high power-high speed), there has recently been a surge in research in transition metal nitrides. The inherent mechanical, chemical and high temperature stability of transition metal nitrides make them ideal candidates for high-performance high-temperature electronics. Scandium nitride (ScN) is of particular interest for incorporation into gallium nitride (GaN) based electronics. Stoichiometric ScN is an n-type III-V semiconductor with a moderate band-gap (2.1-2.4 eV) and high reported carrier concentrations (up to 10²¹ cm^-3). With its rock salt structure and lattice constant of 4.51 nm, ScN has great potential for hetero-epitaxial growth on sapphire (Al₂O₃) and magnesium oxide (MgO). In addition, its close lattice match with GaN (<0.1% mismatch) makes ScN a good candidate for use as a buffer layer for hetero-epitaxial GaN on silicon (Si), in ScN-GaN heterostructures, or as an ohmic contact for GaN devices. Incorporation of ScN films into GaN devices requires high quality (i.e. low surface roughness, large grain-oriented crystals, low oxygen contamination) films.

In this work we investigate hetero-epitaxial growth of ScN films on GaN, Al₂O₃ <0001>, and MgO <100> substrates using unbalanced reactive magnetron sputtering with external electro-magnetic coils. The effect of coil current, target power and nitrogen gas fraction on film stoichiometry, microstructure and surface morphology was investigated by correlating film properties, determined through x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy and atomic force microscopy, with the deposition parameters and plasma conditions during film growth. Hall measurements of the films showed that resistivity and mobility were strongly dependent on crystalline quality and ScN crystal orientation. The Hall mobility of (111)-oriented ScN films on (0001) sapphire increased from 0.95 cm²/(V*S) to 7.8 cm²/(V*S) and the resistivity decreased from 1.57x10^-3 W cm^-3 to 6.52x10^-4 W cm^-3 as the full width half maximum of the ScN (001) x-ray diffraction peak decreased. The transport properties of the (100)-oriented ScN were significantly better than those of the (111)-oriented films with mobilities > 80 cm-2/(V*s) and resistivities < 1.77 x10^-5 W cm^-3_.