Sputter epitaxy of AlN and GaN on Si for device applications

Abstract

Sputtering epitaxy is a low cost process allowing large area deposition at lower growth temperatures than metalorganic vapour phase epitaxy (MOVPE) and may ease e.g. integration with Si CMOS technology. We present high quality AlN and GaN epitaxial layer structures grown on Si(111) substrates by reactive magnetron sputtering. By optimizing nucleation and growth on Si(111) substrates AlN layers are obtained with twist and tilt values comparable to MOVPE grown samples and with very low surface roughness free of any columnar structure. Also the entire compositional range of AlGaN has been addressed by co-sputtering of Al and Ga. Thin undoped buffer layer samples show high breakdown field strengths well above 1×106 V/cm which is prerequisite for FET applications. We also report on reactive sputtering of material combinations that are largely inaccessible to MOVPE, e.g., transition metal nitrides and AlScN.