MATERIAL AND ELECTRICAL CHARACTERIZATION OF POLYCRYSTALLINE BORON-DOPED DIAMOND FILMS GROWN BY MICROWAVE PLASMA CHEMICAL VAPOR-DEPOSITION

Crystal/material quality and electrical properties of B-doped diamond films synthesized by microwave plasma chemical vapor deposition were investigated. Raman spectroscopy verified the presence of diamond and indicated that the crystal quality increased with B doping. Secondary-ion mass spectroscopy showed that the B/C ratios in the films were larger than the B/C ratios in the gas phase, possibly due to differences in B and C sticking coefficients. Electrode patterns of Pt were fabricated on the films and electrical properties were investigated. On undoped diamond films with a residual B concentration of approximately 5 x 10(17) cm-3, these contacts were rectifying with small reverse leakage currents and on B-doped diamond films with a B concentration of 200 and 400 ppm, they yielded ohmic behavior. The temperature dependence of the resistivity showed that these doped films had activation energies, an order of magnitude smaller than that associated with the B impurity level in diamonds. The small activation energies associated with these heavily doped films suggest that an impurity band conduction plays an important role. Experimentally determined Hall mobility of the films was also interpreted qualitatively by an impurity band conduction mechanism and effects of grain boundaries and sp2 components on the transport properties are considered to be small for heavily doped films.