Light B Doping by Ion Implantation into High‐Purity Heteroepitaxial Diamond

The low‐concentration boron doping is performed from 1016 to 1018 cm−3 by ion implantation into heteroepitaxially synthesized large‐area diamond and electrical properties are investigated. Photoluminescence analysis is first carried out to clarify the optical properties of the heteroepitaxial diamond substrate. As a result, defect complexes of nitrogen‐vacancy and silicon‐vacancy are hardly detected in this substrate, suggesting that optically high‐purity diamond can be accomplished by heteroepitaxial growth. Then, the electrical properties of resistivity, mobility, carrier concentration, and conductive type by Hall effect measurements are investigated. For the samples with doping concentrations higher than 1016 cm−3, the electrical activation of implanted B acting as acceptors is confirmed. The compensation ratio for the sample with 3.5 × 1017 cm−3 concentration reaches 76%, indicating the presence of compensating donor‐like centers. With increasing the doping concentration to 3.5 × 1018 cm−3, the compensation ratio is significantly reduced to 35%. The observed mobility of the higher doped sample takes almost the ideal value observed for the sample doped by chemical vapor deposition process. It is suggested that the heteroepitaxial synthesis of large‐area and high‐purity substrates should contribute to the further development of the application to electronic, optical, and sensing devices in the future. The present Hall mobility observed for B‐doped diamonds compares with previously reported ones around room temperature as a function of acceptor B concentration. It is clearly found that the mobility of the sample with a doping concentration of 3.5 × 1018 cm−3 is close to the ideal value.