Growth and characterization of GaN on c-plane (0001) sapphire substrates by plasma-enhanced molecular beam epitaxy

Abstract

GaN films were grown on the c‐plane of sapphire substrates by plasma‐enhanced molecular beam epitaxy equipped with an electron‐cyclotron resonance (ECR) source. Sapphire substrates were cleaned by a hydrogen plasma treatment, obviating the need for perilous elevated temperatures. ECR sources are plagued with high energetic ions, particularly at high microwave power levels, where they cause damage in the growing films. To circumvent this problem, we systematically optimized the growth conditions and other pertinent parameters for optimum layer quality. Among the parameters optimized were the magnetic field strength, microwave power, nitrogen over‐pressure, and growth temperature. The quality of the GaN layers were evaluated by electrical and structural measurements as well as observing the surface morphology.