Characterization of Boron-Doped Diamond Epitaxial Films

Abstract

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, CH₄and B₂H₆at a CH₄concentration 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 3×10²⁰cm^-3. Schottky diodes were fabricated using Al for Schottky contacts and Ti for ohmic contacts. Rectifying properties were degraded at high boron concentration.