Role of AlN/GaN Multilayer in Crack-Free GaN Layer Growth on 5'φ Si (111) Substrate

摘要

The growth of high-quality and crack-free GaN layers on a 5"φ Si (111) substrate has been carried out in metal-organic vapor phase epitaxy. A high-temperature-grown AlN/GaN multilayer buffer was inserted between a GaN layer and a Si substrate. To improve the crystalline quality of GaN and minimize the degree of wafer bending, the structural parameters of an AlN/ GaN multilayer (e.g. number of pairs and thickness of each layer) were examined. From the results, two models of strain relaxation in the multilayer, namely, the introduction of a dislocation in the multilayer and the deformation of a strain field by a three-dimensional structure of AlN layers, are suggested. In addition, another role of the AlN/GaN multilayer structure, that of inducing compressive distortion in a subsequent GaN layer, was confirmed. On the AlN/GaN multilayer, a 1-μm-thick GaN layer was grown without crack formation. A dislocation density of 5 x 10~9 cm~(-2) determined by atomic force microscopy and a (002) X-ray rocking curve full width at half maximum of 700 arcsec were obtained in the 5"φ Si wafer region.