N-doped hydrogenated nanocrystalline cubic SiC (nc-3C-SiC:H) thin films were deposited on p-type crystalline Si (c-Si) substrates by hot-wire chemical vapor deposition from a SiH4/CH4/H-2/N-2 gas mixture. The current density-voltage and the admittance characteristics of the nc-3C-SiC:H/c-Si heterojunction diodes were investigated. As the H-2 gas flow rate (F(H-2)) increased from 25 to 100 sccm, the ideality factor and saturation current density deceased from 1.87 to 1.47 and 1.6 x 10(-7) to 9.9 x 10(-9) A/cm(2), respectively. However, they increased to 1.82 and 3.0 x 10(-7) A/cm(2), respectively, when F(H-2) was further increased to 1000 sccm. The relaxation time, evaluated from the admittance characteristics, decreased from 2.9 x 10(-5) to 2.4 x 10(-6) s with an increase in F(H-2). The apparent built-in voltage, evaluated from the capacitance-voltage characteristics, decreased from 1.05 to 0.60 eV. These findings were mainly caused by interfacial defects, generated by a high density of H radicals during the nc-3C-SiC:H deposition process. The interfacial defect density increased with an increase in F(H-2), resulting in deterioration of the diode characteristics. (C) 2014 Elsevier Ltd. All rights reserved.