A high-performance broad band UV/visible photodetector has been successfully fabricated on a fully wide bandgap ZnO/ZnS type-II heterojunction core/shell nanowire array. The device can detect photons with energies significantly smaller (2.2 eV) than the band gap of ZnO (3.2 eV) and ZnS (3.7 eV), which is mainly attributed to spatially indirect type-II transition facilitated by the abrupt interface between the ZnO core and ZnS shell. The performance of the device was further enhanced through the piezo-phototronic effect induced lowering of the barrier height to allow charge carrier transport across the ZnO/ZnS interface, resulting in three orders of relative responsivity change measured at three different excitation wavelengths (385, 465, and 520 nm). This work demonstrates a prototype UV/visible photodetector based on the truly wide band gap semiconducting 3D core/shell nanowire array with enhanced performance through the piezo-phototronic effect.

The piezo‐phototronic effect is of immense importance for improving the performance of optoelectronic nanodevices. This is accomplished by tuning the charge carrier generation, separation, and transport under the influence of the inner piezopotential. In this paper, a broad band photodetector is demonstrated that is based on II‐VI binary CdSe/ZnTe core/shell nanowire arrays, in which photodetection is greatly enhanced by the piezo‐phototronic effect. The photodetector performance under UV (385 nm), blue (465 nm), and green (520 nm) illumination infers a saturation free response with an intensity variation near two orders of magnitude, where the peak photocurrent (125 μA) is two orders higher at 0.25 kilogram force (kgf) compared to no load (0.71 μA). The resulting (%) responsivity changed by four orders of magnitude. The significant increase in responsivity is believed to arise from: 1) the piezo‐phototronic effect induced by a change in the Schottky barrier height at the Ag–ZnTe junction, and in the type‐II band alignment at the CdSe–ZnTe interfaces, in conjugation with 2) a small lattice mismatch between the CdSe and ZnTe epitaxial layers, which lead to reduced charge carrier recombination. This work thus extends the piezo‐phototronic effect to a group II‐VI binary semiconductor heterostructure and demonstrates the importance of the epitaxial interface in a core/shell nanowire photodetector.

To advance the photodetection capabilities of type II core/shell nanowire‐based photodetectors, ZnSe has been employed to coat on ZnO nanowire array creating a type‐II heterojunction core/shell nanowire array with additional lower indirect band gap (≈1.84 eV), via a facile two‐step process of chemical vapor deposition and pulse laser ablation. The integrated photodetector based on the ZnO/ZnSe core/shell structure is capable of detecting the entire range of the visible spectrum, from blue to red excitation source, as well as UV light. The absolute sensitivity and the percentage change in responsivity of the photodetector are enhanced by one and three orders of magnitude, respectively. The whole range visible light photodetection and enhanced photocurrent response are attributed to the unique ZnO/ZnSe energy band realignment and the piezophototronic effect. Moreover, the photodetector exhibits self‐powered photodetection behavior under UV/visible light illumination. This study grants a potential application using ZnO/ZnSe type II heterostructure core/shell nanowire array for broad band UV/visible photodetection in both powered and self‐powered circumstances.