Suppression of Rotational Twins in Epitaxial B12P2 on 4H-SiC

Abstract

B12P2 was grown epitaxially on (0001) 4H-SiC using two different substrate miscuts: a standard 4° miscut toward the [1120] and a custom miscut 4° toward the [1100]. Epitaxy on substrates miscut to the [1120] resulted in highly twinned B12P2 films with a rotational twin density of approximately 70% twin orientation I and 30% twin orientation II. In contrast, epitaxy on substrates tilted toward the [1100] produced films of >99% twin orientation I. A H2 etch model is used to explain the 4H-SiC surface morphology for each miscut prior to epitaxy and demonstrate how the surface steps influence the nucleation of B12P2 twin orientations. Surface steps on substrates miscut to the [1120] tend to be zig-zagged with steps rotated 60° from one another producing B12P2 crystals that nucleate in orientations rotated by 60°, hence forming rotationally twinned films. Steps on substrates tilted to the [1100] tend to be parallel resulting in crystallographically aligned B12P2 nucleation.