Formation Mechanisms of Islands on Cu-Alloyed GaN Grown by Plasma Assisted Molecular Beam Epitaxy

Abstract

Cu-alloyed GaN epilayers were prepared by plasma assisted molecular beam epitaxy in a Ga-rich environment with Cu-to-Ga beam equivalent pressure ratios of 1.2 to 4.8%. Islands enriched with Cu are found on all the GaN epitaxial layers. The islands are composed of a Cu9Ga4 intermetallic phase and GaN with the orientation relationship: [111]Cu9Ga4//[1 10]GaN and (10 )Cu9Ga4//(0001)GaN. The formation mechanisms of the islands are discussed in detail. Wavelength dispersive X-ray spectroscopy analyses indicate that the 1.2 and 4.8% samples contain 0.10 ± 0.02 atom % Cu and 0.04 ± 0.03 atom % Cu, respectively. Both samples show ferromagnetic behavior with a magnetization of in a range of (2.3–5.1) × 103 A/m at saturation. A strategy to suppress the island formation and increase Cu incorporation is accordingly proposed and verified.