Structural investigation of AlInN/AlN/GaN heterostructures

AlInN/AlN/GaN high-electron-mobility transistor (HEMT) structures were grown on undoped-GaN-layers/sapphire templates by metal-organic chemical vapor deposition to investigate the properties of HEMTs with various thickness GaN top layer and AlInN layer having different indium composition. Structural properties of HEMTs was studied by high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM), and electrical properties was characterized by Hall Effect measurements. Mosaic model was also used in order to evaluate the mosaicity of GaN and AlN layers in the structures. HRXRD results show that screw dislocation density in GaN rises initially and diminishes afterwards in increased In content, while edge type of dislocation rises initially and diminishes afterwards. The mosaic defect nature of AlN and GaN have the same tendency and representation of AlInN in the structure. AFM analysis indicated that GaN surface has clear atomic steps in case of increasing thickness of the top layer. Hall mobility and carrier density of HEMT samples depend on mosaic defect properties monotonously.