Controlled coalescence of MOVPE grown AlN during lateral overgrowth

Abstract

The substrate miscut orientation of c-plane sapphire has an impact on the lateral growth and coalescence of AlN during epitaxial lateral overgrowth of patterned AlN/sapphire templates. A faster and more homogeneous coalescence was observed for substrates with a miscut orientation of 0.25° toward the m-direction compared to 0.25° toward the a-direction of the sapphire. A reduction of V/III ratio during overgrowth leads to an increase of lateral growth rate and therefore to a faster coalescence. The layer thickness at coalescence was clearly determined by in-situ reflectance measurements during the overgrowth. The coalescence can be controlled by carefully choosing the parameters influencing lateral growth like substrate miscut, process temperature and V/III ratio.