Boron atoms migration during epitaxial growth of boron-doped single-crystal diamond

Boron-doped diamond (BDD) films are essential for the fabrication of electronic devices with P+ or P− layers. However, the boron atoms in the intrinsic diamond substrates due to the concentration gradient may affect the height of the Schottky barrier based on these BDD films. BDD films with different concentrations of boron atoms were deposited on chemical vapor deposition (CVD) diamond seeds by microwave plasma chemical vapor deposition. Laser confocal Raman spectroscopy was utilized to investigate the migration of boron atoms during the CVD deposition process. The results indicate that the diffusion depth is below 20 μm with a boron atom concentration of 1020 cm−3 at a deposition time of 10 h. The boron atom diffusion depth is below 8 μm at a fixed CH4/H2 ratio of 2% after 5 h deposition. The characteristic peak of boron atoms is not detected by Raman spectroscopy after 3 h deposition, while the infrared spectrum indicates that the boron atom concentration is more than 1018 cm−3. Consequently, the boron atom concentration and the diffusion depth in CVD seeds can be regulated by controlling the CH4/H2 ratio and the deposition time. Planar diamond-based Schottky diodes based on the prepared P+ or P− layer exhibit distinct rectification characteristics.