Sputter epitaxy of AlN and GaN on Si(111)

Sputter epitaxy is a low-cost process suited for the deposition of group-III-nitride semiconductors and allowing the deposition on large substrate areas at lower growth temperatures than in metal-organic vapor phase epitaxy (MOVPE). High-quality AlN, AlGaN, and GaN epitaxially grown on Si(111) substrates by reactive magnetron sputtering are demonstrated and details on process parameters are given. With an ammonia-based reactive sputtering process in a high-purity environment, AlN can be grown with high crystalline quality comparable to the best MOVPE-grown samples regarding twist and tilt and with a very low surface roughness, free of the typical columnar structure of sputtered AlN and pits. Also AlGaN, typically required for strain engineering of GaN layers grown on Si, can be grown in the entire compositional range by co-sputtering of Al and Ga. Thin undoped buffer layer samples show high breakdown field strengths well above 2.5 x 10(6) V cm(-1) and demonstrate the possible use for field effect transistor (FET) buffer layers.