Morphology changes of In-doped ZnO nanosheets via ZnCl2 and InCl3 vapor formation during thermal dissipation annealing process and improved UV photoresponse properties

Abstract

Ultraviolet (UV) photodetectors that are fabricated using ZnO thin films exhibit higher photocurrent stability, without a complex filter, than that exhibited by Si-based UV photodetectors. However, the ZnO-based UV photodetectors possess several drawbacks such as slow response speed, low on/off current ratio, and low sensitivity. These drawbacks can be overcome by regulating the number of free carriers and point defects that affect the photocurrent increment and the response speed of the UV photodetectors. In this study, indium (In)-doped ZnO (IZO) thin films were deposited via sol-gel spin coating. Subsequently, the amorphous IZO thin films were crystallized via thermal dissipation annealing (TDA). This facilitated the regulation of the number of point defects and free carriers, and the surface roughness of the IZO thin films decreased with the increase in the doping concentration. The UV photosensitivity of the IZO thin films was higher than that of the undoped ZnO thin films. The IZO thin films also exhibited the highest photoresponsivity and UV photoresponse speed. The technique that was devised in the study was concluded to be a feasible route for the fabrication of ZnO-based UV photodetectors with high photosensitivity, photoresponsivity, and UV photoresponse speed.