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

• N-type nc-3C-SiC:H layers were deposited on p-type c-Si substrates by HW-CVD method.
• The J–V and admittance characteristics of the heterojunction diodes were investigated.
• The heterojunction diodes with high performance were obtained at F(H2) = 100 sccm.
• The built-in voltage of the diodes was about 1.05 eV.

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 100 sccm, the ideality factor and saturation current density deceased from 1.87 to 1.47 and 1.6 × 10−7 to 9.9 × 10−9 A/cm2, respectively. However, they increased to 1.82 and 3.0 × 10−7 A/cm2, respectively, when F(H2) was further increased to 1000 sccm. The relaxation time, evaluated from the admittance characteristics, decreased from 2.9 × 10−5 to 2.4 × 10−6 s with an increase in F(H2). 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(H2), resulting in deterioration of the diode characteristics.