Growth behavior of boron-doped diamond in microwave plasma-assisted chemical vapor deposition using trimethylboron as the dopant source

Cubo-octahedral diamond crystals were formed by microwave plasma-assisted chemical vapor deposition of methane and hydrogen on a Si(100) wafer. Trimethylboron was then added to the gas phase as the boron source, and diamond was homoepitaxially deposited on the {100} and {111} of the seed crystals. The growth rate, which was determined from geometrical changes in the crystals, was affected by the type of diamond faces, as well as the boron to carbon (B/C) ratio in the gas phase. The rate decreased with increasing the B/C ratio at concentrations below 400 ppm, and was independent of the B/C ratio at concentrations in excess of 500 ppm. Furthermore, boron-doped diamond films were formed on single-crystalline (100) and (111) diamond substrates by varying the B/C ratio in the gas phase, and depth profiles of boron and hydrogen were determined by secondary ion mass spectroscopy. The boron content in the (100) and (111) diamond increased with increasing B/C ratio in the gas phase and was 9 × 10¹⁷ cm^-3 and 1 × 10¹⁹ cm^-3, respectively, when the B/C ratio in the gas phase was 2000 ppm.