The authors demonstrate that the electric conductivities of cubic and hexagonal boron nitride (c-BN and h-BN) thin films increased markedly by the in situ doping of zinc. The doped films were electrically semiconducting, and conductivities at room temperature increased from 10~(-8) to 10~(-2) Ω~(-1) cm~(-1) with increasing zinc concentration from 400 to 20 000 ppm. Activation energies for electric conduction (E_c) of c-BN decreased from 0.3 to 0.1 eV with increasing zinc concentration, suggesting feasible shallow-level doping. On the other hand, h-BN thin films showed approximately 0.1 eV higher E_c than those of c-BN's, due to the formation of defective B-B bonds.
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