Effect of boron incorporation on growth behavior of BGaN/GaN by MOVPE

In the family of III-nitride compounds, BxGa1−xN is particularly attractive because it can be lattice matched to AlN or SiC substrates. In this work we studied in detail the relationship between morphology, composition, and boron surface segregation in BxGa1−xN layers grown on GaN template substrates by MOVPE. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations reveal the formation of large polygonal crystallites for the growth regimes with triethylboron (TEB/III) ratios and film thicknesses exceeding the optimum values. XPS measurements demonstrate that the boron content at the surface is higher compared to that in the volume of the film and it increases with the TEB/III ratio and/or the film thickness. From a given surface boron segregation, drastic variations in the film morphology occur and are attributed to phase separation. Our study demonstrates the possibility to grow BxGa1−xN/GaN/sapphire films of a single phase up to x=3.6% by reducing the thickness of the BGaN layers.