Defect-Mediated In-Plane Electrical Conduction in Few-Layer sp²-Hybridized Boron Nitrides

In-plane electrical conduction in sp²-hybridized boron nitride (sp²-BN) is presented to explore a huge potential of sp²-BN as an active material for electronics and ultraviolet optoelectronics. Systematic investigation on temperature-dependent current-voltage ( I- V) characteristics of a few-layer sp²-BN grown by metal-organic vapor-phase epitaxy reveals two types of predominant conduction mechanisms that are Ohmic conduction at the low bias region and space-charge-limited conduction at the high bias region. From the temperature-dependent I- V characteristics, two shallow traps with activation energies of approximately 25 and 185 meV are observed. On the basis of the near-edge X-ray absorption fine-structure spectroscopy, boron-boron (B-B) homoelemental bonding which can be related to grain boundary and nitrogen vacancy (V_N) are proposed as the origin of the shallow traps mediating the in-plane conduction in the sp²-BN layer. In addition, a drastic enhancement in the electrical conductivity is observed with the increasing amount of V_N that acts as a donor, implying that controlled generation of V_N can be an alternative and better approach for the n-type doping of the sp²-BN film rather than ineffective conventional substitutional doping methods.