Growth of coherent BGaN films using BBr₃ gas as a boron source in plasma assisted molecular beam epitaxy

Incorporating boron into gallium nitride to make B_xGa_1-xN solid solutions would create an avenue for extreme alloys due to the fact that wurtzite phase BN has a larger band gap and smaller lattice parameters compared to GaN. In this paper, the authors report the growth of high crystal quality, random alloy B_xGa_1-xN thin films with x up to 3.04% grown on (0001) Ga-face GaN on sapphire substrates using plasma assisted molecular beam epitaxy and BBr₃ gas as a B source. High resolution x-ray diffraction was used to measure both the c plane spacing and the strain state of the films. It was determined that the films were fully coherent to the GaN substrate. Elastic stress-strain relations and Vegard's law were used to calculate the composition. Atom probe tomography was used to confirm that the B_xGa_1-xN films were random alloys. In addition to demonstrating a growth technique for high crystal quality B_xGa_1-xN thin films, this paper demonstrated the use of BBr₃ as a novel B source in plasma assisted molecular beam epitaxy.