Heteroepitaxial growth of boron phosphide on 3C-SiC/Si(100) and AlN/sapphire(0001) substrates

The quality of the heteroepitaxial boron phosphide (BP) films is dependent on the properties of the substrate employed and the growth conditions. In this work, the structural properties of BP epitaxial films on 3C-SiC/Si(100) and AlN/sapphire(0001) were evaluated. The former substrate has the same symmetries as BP, thus it eliminates in-plane twinning. The latter has a low lattice constant mismatch and is composed of isoelectronic elements, making it less likely to cause unintentional doping. High quality films were deposited using PH₃+B₂H₆+H₂ system at temperatures ranging from 1000°C-1100°C and atmospheric pressure. Optical and scanning electron microscopy revealed smooth morphologies with predominantly BP(111) and (100) on AlN/Sapphire(0001) and 3C-SiC/Si(100) substrates respectively. Raman spectroscopy showed intense, sharp phonon peak located at around 825 cm^-1. XRD revealed the BP films to be single crystalline with peak height ratios of BP(111) to BP(220) to be 561 on AlN/sapphire and BP(100) to BP(220) to be 2650 on 3C-SiC/Si. X-ray topography revealed in-plane twinning was absent for BP on 3C-SiC/Si but was detected for BP on AlN/sapphire. This is a consequence of exact crystal symmetry matching in the former case, but a mismatch in the latter case; three-and six-fold rotational symmetries for BP and AlN respectively.