Chemically synthesized nanowire TiO2/ZnO core-shell p-n junction array for high sensitivity ultraviolet photodetector

Abstract

A sol-gel-based ultrathin TiO2 lamination coating was adapted to a hydrothermally grown ZnO nanowire array to realize an all-oxide ultra-sensitive p-n photodiode. The core-shell heterojunction—the key component of the device—is composed of a 5–10 nm thick p-type Cr-doped TiO2 nanoshell and n-type single-crystalline ZnO nanowires (50 nm radius). Owing to the enhanced light scattering and carrier separation in the core-shell architecture, this device exhibits the highest performance among the ZnO nanowire-based photodetectors. At a moderate reverse bias of −5 V and under ultraviolet light illumination at 104 μW, it shows a switch current ratio of 140 and a responsivity as large as 250 A/W, while it shows nearly no response to the infrared and visible light.

Role of Junction Geometry in Determining the Rectification Performance of Nanostructured TiO₂-Based p-n Junctions

“…However, increase in doping density produces two detrimental effects on device property: 1) reduction in breakdown voltage and 2) increased Joule heating [1]. To overcome these limitations, physical geometry of the p-n junction was used as an important parameter in tuning the rectification efficiency without any significant variation in doping density of the corresponding semiconductors [3]- [5].…”

“…Therefore, the development of p-n homojunction with large junction area, employing wide bandgap semiconducting materials [such as ZnO, titanium dioxide (TiO 2 ), and so on], is a key focus area for the device researchers across the globe [3], [6], [7]. These materials offer the additional advantage of formation of different nanostructures (such as nanorod, nanoparticle, nanoflower, and so on), which eventually pave the path for high surface area/geometry.…”

Hybrid Fabrication of Highly Rectifying <inline-formula> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> Homojunction Based on Nanostructured TiO₂

“…W IDE band gap transition metal oxide (TMO) based p-n junctions find potential applications in modern electronics, particularly in photo-catalysis and chemical sensing [1], [2]. While in photo-catalytic application, the p-n junction enhances the charge separation capacity of the solar cell [1], in chemical sensor application, higher value of the built in potential (of the p-n junction) leads to a strong sensor signal on exposure to the target species [2].…”

“…While in photo-catalytic application, the p-n junction enhances the charge separation capacity of the solar cell [1], in chemical sensor application, higher value of the built in potential (of the p-n junction) leads to a strong sensor signal on exposure to the target species [2]. In the recent past, such TMO (like ZnO, NiO etc.)…”

“…In the recent past, such TMO (like ZnO, NiO etc.) based p-n junctions has attracted the research interests, particularly aiming at the fabrication of rectifying and light emitting devices [1]- [3].…”