Fabrication of a large-area Al-doped ZnO nanowire array photosensor with enhanced photoresponse by straining

The photosensing properties of flexible large-area nanowire (NW)-based photosensors are enhanced via in situ Al doping and substrate straining. A method for efficiently making nanodevices incorporating laterally doped NWs is developed and the strain-dependent photoresponse is investigated. Photosensors are fabricated by directly growing horizontal single-crystalline Al-doped ZnO NW arrays across Au microelectrodes patterned on a flexible SiO ₂/steel substrate to enhance the transportation of carriers and the junction between NWs and electrodes. The Raman spectrum of the Al:ZnO NWs, which have an average diameter and maximum length of around 40 nm and 6.8 μm, respectively, shows an Al-related peak at 651 cm ^-1. The device shows excellent photosensing properties with a high ultraviolet/visible rejection ratio, as well as extremely high maximum photoresponsivity and sensitivity at a low bias. Increasing the tensile strain from 0 to 5.6% linearly enhances the photoresponsivity from 1.7 to 3.8 AW ^-1 at a bias of 1 V, which is attributed to a decrease in the Schottky barrier height resulting from a piezo-photonic effect. The high-performance flexible NW device presented here has applications in coupling measurements of light and strain in a flexible photoelectronic nanodevice and can aid in the development of better flexible and integrated photoelectronic systems.