Substrate temperature optimization for heavily-phosphorus-doped diamond films grown on vicinal (001) surfaces using high-power-density microwave-plasma chemical-vapor-deposition

• Heavily phosphorus-doped (001) diamond films grown using high-power-density MWPCVD.
• Some BE emission peaks were observed in cathodoluminescence measurements at 83 K.
• Crystalline steps on surface should play an important role on the P-doping diamond growth.
• Crystalline quality of the films was improved by controlling the off-angle of the substrates.

We have investigated the growth condition suitable for homoepitaxial diamond growth of phosphorus (P)-doped films on vicinal (001) substrates with a misorientation angle of 5° using the high-power-density microwave-plasma (MWP) chemical-vapor-deposition (CVD). The P-doped layers were grown with H2-diluted (1%) CH4 gas containing P(CH3)3 with P/C ratio of 0.99% at various substrate temperatures ranging from 960 to 1210 °C by using a conventional MWPCVD system with a quartz-tube chamber. It is found from exciton-related cathodoluminescence spectra taken at ≈80 K and secondary ion mass spectrometry profiles that reasonably-high-quality P-doped layers with containing a substantial amount of substitutional P donors were grown on vicinal (001) substrates only at substrate temperatures of ≈1160 °C although the sample surface completely lost the original flatness with a roughness of ≈0.3 nm. This indicates that the suitable process window should be rather narrow for the P-doped diamond homoepitaxial growth on the vicinal (001) substrate using the present MWPCVD with 1% CH4 source gas and that the crystalline steps should play an important role on the growth process appropriate for the P atom incorporation to substitutional sites.