Preparation, properties, and characterization of boron phosphide films on 4H- and 6H-silicon carbide

Epitaxial growth of boron phosphide (BP) films on 4H- and 6H-SiC(0001) substrates with on- and off-axis orientations was investigated in this study. The films were prepared by chemical vapor deposition using phosphine and diborane as reactants over a temperature range of 1000 °C-1200 °C. The effects of growth parameters such as temperature, reactant flow rates, substrate type, and crystallographic orientation on BP film properties were studied in detail. The epitaxial relationship between BP film and 4H-and 6H-SiC substrate was (111)BP<112¯>BP||(0001)SiC<11¯00>SiC. Film quality, determined by preferred crystalline orientation and grain size, improved with temperature and PH₃/B₂H₆ flow ratio, as indicated by scanning electron microscopy, x-ray diffraction, atomic force microscopy and Raman spectroscopy. In addition, smoother films were obtained when the diborane flow rate was reduced. Rotational twinning in BP films was absent on 4H-SiC(0001) tilted 4° towards [11¯00], but was confirmed on both 4H-SiC(0001) tilted 4° towards [12¯10], and on-axis 6H-SiC(0001) substrates by synchrotron white beam x-ray topography technique.