Boron tribromide provides way to grow boron crystals with molecular beam epitaxy
Boron tribromide provides way to grow boron crystals with molecular beam epitaxy lead image
Like other group III-nitrides, boron containing III-nitrides have predicted potential for a variety of semiconductor applications, ranging from light-emitting diodes to high-frequency power electronics. Growing boron-containing crystals, however, can be challenging due to the element’s high melting point. A new experimental approach provides one way to create a thin film that incorporates boron.
Cramer et al. have previously demonstrated a new injection system for growing crystals of a boron-containing nitride alloy, BGaN. Using boron tribromide (BBr3) gas as the boron source and plasma-assisted molecular beam epitaxy, the group grew high-quality crystals. This study explores the advantages and limitations of the technique.
“This is a novel technique to grow with an element which has been difficult to grow with historically,” said Richard Cramer, an author on the paper. “This isn’t the only technique being developed so it’s one more tool in the toolbox of how to grow with boron.”
Relatively little is known about the properties of the proposed boron-containing group III-nitrides, in part because the stable phase of boron nitride is layered hexagonal in shape, unlike the wurtzite crystal structure other group III-nitrides take on.
The BBr3 systems grew coherent BGaN films with boron concentrations up to 3 percent on the group III site of the crystal. X-ray diffraction showed that the thin films were fully coherent at thicknesses up to 280 nanometers.
The group also found, however, that the crystals have high levels of bromine impurities. Such impurities currently limit applications of the thin films.
Cramer hopes to continue investigating ways to minimize incorporation of bromine into the crystals in addition to exploring the growth of other types of boron nitrides.
Source: “BBr3 as a boron source in plasma-assisted molecular beam epitaxy,” by Richard C. Cramer, John English, Bastien Bonef, and James S. Speck, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films (2019). The article can be accessed at https://doi.org/10.1116/1.5117240 .
