Impact of nitrogen doping on homoepitaxial diamond (111) growth

The impacts of nitrogen (N) doping on the lateral growth mode during two-dimensional (2D) nucleation, on the growth rate, and the incorporation of nitrogen (concentration [N]) of (111)-oriented diamond films were investigated by modulating the [N2]/[CH4] gas admixture ratio. The 2D nucleation density first increased with increasing [N2]/[CH4] ratio between 0.02 and 20%. Further increase of the [N2]/[CH4] ratio to up 200% caused a decrease of the nucleation density. The growth rates showed the similar N-doping dependence as the nucleation density variation. This is attributed to an initial increase of CN radicals in the regime 0.02 to 20%, followed by a reduction of CHx radicals in the regime 20 to 200%. The nitrogen incorporation concentration increases with increasing the [N2]/[CH4] ratio. The highest nitrogen concentration with 2 × 1020 atoms/cm3 is detected with [N2]/[CH4] = 200% and a relatively low nucleation density is achieved. These results are beneficial for the optimized formation of nitrogen-vacancy centers used in a quantum metrology and for device application such as inversion-channel diamond MOSFETs.