Coherent Growth of AIN/GaN Short-Period Superlattice with Average GaN Mole Fraction of up to 20% on 6H-SiC(0001) Substrates by Plasma-Assisted Molecular-Beam Epitaxy

摘要

To obtain a high-crystalline-quality AIN/GaN short-period superlattice with higher average GaN mole fraction, the effects of the thicknesses of AIN barrier and GaN well layers on the superlattice growth were investigated. Coherent growth with an average GaN mole fraction of 20% was realized by reducing the AIN barrier layer thickness to 8 bilayers (BL) while keeping the GaN well layer thickness at 2 BL. Further reduction in the AIN barrier layer thickness resulted in lattice relaxation and degradation of the crystalline quality. Grown layers with various well and barrier thicknesses were investigated by transmission electron microscopy, X-ray diffraction, and atomic force microscopy.