White-light emitting diode array of P⁺-Si/aligned N-SnO ₂ nanowires heterojunctions

We report on the fabrication and optoelectronic properties of p-n heterojunction arrays of p⁺-type Si and aligned n-type SnO ₂ nanowires with high rectification ratios of >10⁴ at ±15 V. The electrical stability of the p-n heterojunction devices was improved by coating the junction with poly(methylmethacrylate) to minimize the degradation of the interface layer at the junction. As a photodiode an enhanced UV photosensitivity higher than 10² was recorded under reverse bias. Using a large forward bias in the light-emitting diode mode white light was emitted from the large-scale heterojunction devices with at least three broad peaks in the visible range, which can be attributed to the interband transitions of the injected electrons or holes mediated by an interfacial SiO₂ layer with a contribution of trap-level energies. These results indicate the high potential of Si/SnO₂ nanowires heterojunctions as optoelectronic devices with proper tuning of the recombination center at the junctions. The characterization of p⁺-Si/n-SnO₂ nanowire heterojunction diode arrays with ideal rectification behavior is reported. Their high UV-photosensitivity under reverse bias voltages and white-light electroluminescence at forward bias enlarge their future application in optoelectronic devices.