Growth and characterization of GaN epilayer grown on on-axis Si (100) substrate by metalorganic chemical vapor deposition

3^rd International Conference and Exhibition on Materials Science & Engineering

October 06-08, 2014 Hilton San Antonio Airport, USA

Kwadwo Konadu Ansah-Antwi, Hongfei Liu, Chengguo Li, Jian Wei Ho, Ping Yang, Parviz Hajiyev, Ting Yu, Lay Ting Ong and Soo Jin Chua

Accepted Abstracts: Material Sci Eng

Abstract :

This presentation will be in two parts: In the first part, we shall look at a facile method for reducing the threading dislocation density (TDD) in GaN epilayer grown on on-axis Si(100) substrates without the use of complex compensating and interlayers. On-axis substrates are used in this work CMOS compatibility reasons. We report on the reduction of threading dislocation density (TDD) of GaN epilayer grown on the {111} exposed surface of a V-groove formed on Si(100) substrates by metalorganic chemical vapor deposition (MOCVD). The V-grooves were either aligned parallel or misoriented at an angle α (α=2, 4 or 6) towards the <011> crystallographic direction. The intentional introduction of misorientations of the masked trenches resulted in steps and terraces on the exposed {111} surface. It is found that the full width at half maximum (FWHM) of both out-of-plane (0002) and in-plane (10-11) rocking curves of GaN grown on the 6o misoriented groove template was narrower by a factor of 2 compared to the other samples indicating a reduction in both screw and edge dislocation densities (TD). The lithographically defined grooves are defined as either discontinuous or continuous based on whether there are spaces separating the grooves or not. Raman scattering results revealed that, GaN grown on the discontinuous V-grooved samples was unintentionally doped with free carriers from the SiNx mask, resulting in the disappearance of the A1(LO) phonons mode. Transmission electron microscopy (TEM) results corroborated TDD reduction of GaN grown on the 6o misoriented groove template via dislocation bending towards the edge facets of the 3D AlN buffer islands that nucleated on the vicinal Si{111} interface. Vicinal surface with step height (~19 nm) and terrace length (~450 nm) of certain geometric parameters are found to be effective in reducing the total TDD in GaN epilayer. The second part of the presentation focuses on the growth of semipolar GaN on on axis Si(100) substrate. We present results obtained in our research group on the growth of GaN on Si(100) substrates with different template patterns. The crystal quality was investigated by high resolution X-ray diffraction (HR-XRD) and the morphology of the as-grown GaN was characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and optical microscope. The optical properties are studied by Raman scattering and photoluminescence spectroscopy. Finally but not least, the threading dislocation density within the GaN was investigated by transmission electron microscope (TEM).