Mutual interaction of N, B, and O during heteroepitaxial diamond growth: Triggering the nitrogen induced growth acceleration

The mutual interaction of N, B, and O during heteroepitaxial diamond growth by microwave plasma chemical vapour deposition (MPCVD) is investigated. The study comprises in situ growth rate measurements by laser reflection interferometry (LRI) and the monitoring of impurity containing gas phase species like CN and BH by optical emission spectroscopy (OES). In the gas phase, among the combinations (N, B), (N, O), and (B, O) only the latter pair shows a measurable mutual influence. In contrast, growth rate measurements reveal a strong interaction also for the couple (N, B). It is found that the high growth rate enhancement obtainable by nitrogen addition is completely suppressed by boron contamination at ppm levels. At even lower boron concentrations a step‐like behaviour is observed, i.e., the nitrogen is initially inactive before it develops its effect above a defined threshold concentration. Addition of oxygen to the gas mixture proves to be an effective method to push this threshold to lower nitrogen concentrations and to trigger the action of nitrogen even in highly contaminated reactors. We estimate that the presence of 1 boron atom can cancel the effect of 1000 nitrogen atoms in the gas phase.