Dependence of defect structure on In concentration in InGaN epilayers grown on AlN/Si(111) substrate

Abstract

InGaN epilayers with different indium concentrations have been grown on a 100-nm-thick AlN/n-Si(111) template using plasma assisted molecular beam epitaxy. The sample with the lowest indium (In) content is found to exhibit the highest crystallinity. Furthermore, the types as well as the densities of the threading dislocations in InGaN have been analyzed via high resolution X-ray diffraction measurements. The InGaN epilayers have been described as mosaic crystals, which are characterized by biaxial strain, hydrostatic strain, and mean tilt and twist angles. It is observed that the biaxial strain increases with increasing indium content and the hydrostatic strain decreases with increasing indium content in the films. The twist and tilt angles have also been correlated with the edge and screw dislocation densities, respectively. Furthermore, it has been concluded that point defects dominate in samples with a lower In content whereas trench defects and sub-interfacial extended defects dominate in samples with a higher In content.