A combined growth process for state-of-the-art GaN on silicon

This study aims to simplify the heteroepitaxy of GaN on Si while keeping state-of-the-art III-nitride materials. The originality of this work is to combine the advantages of both NH3-MBE and metal organic chemical vapor deposition (MOCVD) growth techniques. First, the structural quality of AlN is assessed by AFM, XRD measurements, and TEM. Terraces and atomic step edges are observed by AFM showing a good structural quality of the AlN epilayer. TEM investigation reveals a sharp and well-controlled AlN/Si using NH3-MBE. Then, a 2-μm thick smooth GaN layers are obtained by MOCVD on top of these AlN templates with the use of a SiNx treatment allowing a 3D growth mode able to induce an efficient dislocation filtering to be obtained. GaN structural properties, measured by XRD, AFM, and SEM, are discussed and compared to GaN-on sapphire (Al2O3). In addition, the stress in the GaN layers grown on these AlN templates with or without a SiNx treatment is assessed. GaN epilayers with a dislocation density in the range of few 108 dislocations per cm2 have been achieved using a single AlN buffer layer (no interlayer) and only 2 μm of GaN.