In situ doping of epitaxial diamond with germanium by microwave plasma CVD in GeH4-CH4-H2 mixtures with optical emission spectroscopy monitoring

We report the growth of Ge-doped homoepitaxial diamond films by microwave plasma CVD in GeH4-CH4-H-2 gas mixtures at moderate pressures (70-100 Torr). Optical emission spectroscopy was used to monitor Ge, H, and C-2 species in the plasma at different process parameters, and trends for intensities of those radicals, gas temperature, and excitation temperature, with variations of GeH4 or CH4 precursor concentrations, were investigated. The film deposited on (111)-oriented single crystal diamond substrates in a high growth rate regime revealed a strong emission of a germanium-vacancy (GeV) color center with a zero-phonon line at approximate to 604 nm wavelength in photoluminescence (PL) spectra, confirming the successful doping. The observed PL shift for the GeV defect is caused by stress in the films, as evidenced and quantified by Raman spectra. These results suggest that in situ doping with Ge using a GeH4 precursor is a convenient method of controlling the formation of GeV centers in epitaxial diamond films for photonic applications.

Automated summary

This study reports the growth of Ge-doped homoepitaxial diamond films using microwave plasma CVD at moderate pressures, monitoring the plasma with optical emission spectroscopy and confirming successful doping through photoluminescence and Raman spectra. The results suggest that in situ doping with Ge using a GeH4 precursor is a convenient method to control the formation of GeV centers in epitaxial diamond films for photonic applications.