Electrical characteristics and carrier injection mechanisms of atomic layer deposition synthesized n-SnO₂/p-Si heterojunction

The SnO₂/Si heterojunction was prepared through depositing SnO₂ thin film onto p-Si substrate by means of atomic layer deposition using TDMASn (tetrakis(dimethylamino)tin) and deionized water as precursors. We found that there were three types conduction process in the SnO₂/Si heterojunction. When the temperature was lower than 340 K, the carrier conduction at low bias mainly was direct tunneling. Whereas, the carrier transport at high bias turned into Fowler-Nordheim (F-N) tunneling. At temperature above 340 K, the carrier injection mechanism showed coexistence of thermionic emission and direct tunneling when the applied voltage was low, while in the high applied voltage region the thermionic emission and F-N tunneling existed simultaneously. The saturated reverse current obtained from the current-voltage characteristic at different temperature indicated that there was no barrier saddle point in the SnO₂/Si heterojunction. The rectification ratio at ± 4.5 V varied from 176 to 327, which was better than traditional ZnO-based heterojunction. The calculated conduction band offset and valence band offset between SnO₂ and Si were 0.68 eV and 2.12 eV, respectively. The smaller conduction band offset compared with the valence band offset led to the control of the electron transport easier than that of the hole transport. We believe the results in this study should be helpful in understanding the interfacial carrier injection mechanism of silicon-based oxide structure at various temperatures and bias voltages.