Current density–voltage and admittance characteristics of hydrogenated nanocrystalline cubic SiC/crystalline Si heterojunction diodes prepared with varying H2 gas flow rates

Abstract

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/H2/N2 gas mixture. The current density–voltage and the admittance characteristics of the nc-3C-SiC:H/c-Si heterojunction diodes were investigated. As the H2 gas flow rate (F(H2)) increased from 25 to 100sccm, the ideality factor and saturation current density deceased from 1.87 to 1.47 and 1.6×10−7 to 9.9×10−9A/cm2, respectively. However, they increased to 1.82 and 3.0×10−7A/cm2, respectively, when F(H2) was further increased to 1000sccm. The relaxation time, evaluated from the admittance characteristics, decreased from 2.9×10−5 to 2.4×10−6s with an increase in F(H2). The apparent built-in voltage, evaluated from the capacitance–voltage characteristics, decreased from 1.05 to 0.60eV. 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(H2), resulting in deterioration of the diode characteristics.