Characterization of a Thick Homoepitaxial CVD Diamond Film

ABSTRACTA thick homoepitaxial CVD diamond film was grown on a large high temperature, high pressure (HTHP) Ha diamond to study the defects present in the CVD film. The HTHP diamond had dimensions of 6 mm x 6 mm x 0.44 mm. The thickness of the diamond was increased to 0.84 mm by microwave plasma CVD. X-ray topographs were taken before and after growth to compare the defects in CVD diamond to those in the HTHP diamond. Prior to growth the substrate was unstrained and the characteristic microstructure of stacking faults and dislocations was observed. There was also a surface relief, visible optically, on the substrate of lines along the [100] which are probably due to polishing. After deposition of the CVD film, the crystal was strained with the film in tension. The defect structure observed throughout the CVD film followed the surface relief of the substrate. Cathodoluminescence spectra indicate that the film contains nitrogen defect complexes which are not present in the substrate. Cathodoluminescence also indicates that there are more non-radiative recombination centers in the film than in the substrate. Electrical results from transient photoconductivity measurements indicate that while the mobilities of the film and the substrate are comparable, the lifetime is much shorter in the film, possibly reflecting the higher concentration of non-radiative recombination centers.