High growth rate homoepitaxial diamond deposition on off-axis substrates

High rate homoepitaxial diamond growth by microwave plasma chemical vapor deposition (MPCVD) was studied. At a gas pressure of 200 mbar and a methane concentration of 10% a maximum growth rate of 30 μm/h was obtained. High pyramidal hillocks with pronounced step bunching on the side faces develop during growth on (001) oriented Ib substrate crystals. The peak of the pyramids is formed by non-epitaxial particles. Using (001) oriented crystals with a vicinal angle greater than the typical inclination angle of the pyramids' side faces is an efficient strategy to suppress the non-epitaxial crystals completely. The characteristic morphological changes on the surface can be explained by the dynamics of nucleation of new lattice planes and their consumption. Homoepitaxial layers with a thickness of up to 1.3 mm were successfully grown in this way. After removal of the nitrogen containing Ib substrate one sample showed a full-width at half maximum (FWHM) of 0.0043° in high resolution X-ray diffraction (HR-XRD) measurements. Most of them were in the range between 0.01° and 0.03°. In Raman spectra, the measured diamond line was extraordinarily narrow with a typical FWHM of about 1.63 cm−1. In addition, the low luminescence background in photoluminescence (PL) spectra excited with the 488 nm line of an Ar+ ion laser proved the excellent quality of the samples.