Nitrogen-related point defects in homoepitaxial diamond (001) freestanding single crystals
Tokuyuki Teraji, Chikara Shinei
Abstract
Controllability of nitrogen doping, types of nitrogen-related defects, and their charge states in homoepitaxial diamond (001) crystals were investigated. For these purposes, 15N-doped 12C-enriched free-standing chemical vapor deposited diamond (001) crystals were grown through long-time growth using 12C-enriched methane as the carbon source gas and 15N-enriched molecular nitrogen as the nitrogen source gas. The formation of non-epitaxial crystallites and growth hillocks was suppressed by the application of the oxygen-adding growth condition. Nitrogen was incorporated uniformly into the crystals, with a concentration variation of less than 10%. About 70% of the total nitrogen was substitutional nitrogen in a neutral charge state Ns0. Hydrogen was incorporated at approximately the same concentration as nitrogen. Both NV and NVH centers were predominantly negatively charged defect structures, i.e., NV− and NHV− centers. The concentrations of NHV− centers were less than 5% of the total nitrogen concentration. Nitrogen concentration in diamond crystals was controlled by changing the N/C gas ratio over a wide doping range from 10 ppb to 10 ppm. Nitrogen incorporation efficiency was found to be (1.5 ± 0.5) × 10−4 in this study.