Kinetical limitations of h-BN MOVPE growth

The MOVPE growth of h-BN (more specifically sp
²
-BN) layers encounters problems concerning growth efficiency, crystallographic quality and a large quantity of optically active point defects of undisclosed nature. Our results show that high quality layers can be grown with continuous or modulated flow methods. Depending on the conditions, the synthesis is limited by insufficient ammonia dissociation, boron diffusion on the surface or probability of chemisorption on atomic steps. Despite the common belief, gas phase parasitic reactions were not observed. It is crucial to control the balance between mass transport, diffusion and desorption from the surface. Supersaturation of TEB leads to a fast nucleation of randomly oriented crystal grains and 3D growth. Epitaxial, two-dimensional (2D) layers can be only obtained with a very low growth rate. The amount of point defects, influencing the optical properties of the layers, depends on the growth conditions and, especially, ammonia supply.