Characterization of boron-doped diamond epitaxial films

Boron-doped diamond epitaxial films were characterized on the dependence of boron concentration by an optical microscope, reflection high-energy electron diffraction, secondary ion mass spectrometry, Hall effect measurement and metal contacts. These films were grown on synthesized single-crystal diamonds(100) by microwave plasma chemical vapor deposition (CVD) using H2, CH4 and B2H6 at a CH4 concentration of CH4/H2=6% and at doping gas ratios of B2H6/CH4=0.83 ppm, 8.3 ppm, and 167 ppm. They were all epitaxially grown and had smooth surfaces. Hall effect measurements were performed in the temperature range of 300 K to 773 K. They indicated that there existed acceptorlike centers other than boron in the films synthesized in the vapor phase. Fermi degeneracy was found to occur at a boron concentration of 3 × 1020 cm-3. Schottky diodes were fabricated using Al for Schottky contacts and Ti for ohmic contacts. Rectifying properties were degraded at high boron concentration.