Leakage current mechanisms and their dependence on composition in silicon carbonitride thin films

Electrical conduction in amorphous silicon carbonitride (a-SiCN:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) is investigated for varying carbon to nitrogen ratios at room temperature. Films deposited with a lower carbon/nitrogen ratio showed two modes of electrical conduction; namely, Schottky emission mode below 2.3 MV cm⁻¹ electric field and Poole–Frenkel mode from 2.3 MV cm⁻¹ up to the breakdown field. Films with higher carbon/nitrogen ratios showed only Poole–Frenkel mode of conduction throughout the entire range of operation up to the breakdown field. The carbon rich films exhibited higher leakage currents attributed to its shallow defect energy levels leading to its higher Poole–Frenkel conductivity. (paper)