Economically detaching transparent and flexible (Al,Ga)N nanowire films with improved photoelectric response in view of ultraviolet photodetectors

Abstract

Gallium nitride-based (GaN-based) nanowire films are promising for various devices requiring high flexibility and/or high transparency, such as detectors and wearable intelligent electronics. In this work, a cost-effective and novel electrochemical procedure has been designed to detach films with (Al,Ga)N nanowires (NWs). Besides the ability of selectively etching, the nitric acid (HNO₃) is found to protect the (Al,Ga)N NWs without too much etching, which is better than the potassium hydroxide (KOH). Therefore, a film comprising a dense ensemble of (Al,Ga)N NWs with both good flexibility and high transparency can be achieved successfully by this lift-off technology. In addition, it is demonstrated that the HNO₃ etching can improve the photoelectric response of ultraviolet (UV) photodetectors significantly. Compared to that of UV photodetectors without HNO₃ etching, the peak responsivity of UV photodetectors with HNO₃ etching is enhanced by about 166% and the corresponding decay time becomes much faster. The removal of the bottom aluminium nitride (AlN) layer and Al-rich (Al,Ga)N shell, as well as the decrease of the surface states and defects can contribute to the improvements.