Wafer-scale MOVPE growth and characterization of highly ordered h-BN on patterned sapphire substrates

Abstract

Layered h-BN were grown on sub-micron size dome patterned sapphire substrates (PSS) by metal organic vapor phase epitaxy (MOVPE) to study the effects of substrate orientations, strain and subsequent thermal stress evolution. Electron micrograph images on the surface of the c-plane sapphire in-between the dome structures show typical wrinkled morphology of layered h-BN, similar to the reference sample surface confirming the high quality h-BN growth. However, the h-BN morphology on the domes exhibited pattern like folding which were drastically different from the h-BN on the c-plane sapphire. Detailed TEM studies show that the h -BN is layered and covers the dome patterns of the sapphire substrates like a “blanket of snow” continuously with localized strain variations induced turbostratic phase insertions. In addition, the local variation in optical emission properties of layered materials, which are dramatically affected by the rippled morphology were also investigated using depth resolved cathodoluminescence. The intensity variation of the 320 nm peak confirms that the BN on dome structures have more strain related defects than the c-plane h-BN. Thus, these results give better insight on the origin of turbostratic BN grains and local control over the structural and optical emission characteristics.