Ga-doped ZnO (GZO) nanostructures with high photoresponse were deposited on the seed layers of GZO thin films via polyethylene glycol (PEG400)-assisted chemical bath method at low temperatures. GZO thin films were prepared on quartz glass substrates by sol–gel spin coating technique. The structural, optical and photoelectrical properties of the GZO nanostructures were investigated. The scanning electron microscopy images showed GZO nanostructures presented nanosheets at 50 and 60 °C and nanopillars at 70 and 80 °C. X-ray diffraction results revealed that GZO nanostructures had a hexagonal wurtzite structure. Room temperature photoluminescence spectra exhibited ultraviolet emission peak and visible emission peak. The defect emission peak of GZO nanostructures was red-shifted from 521 to 571 nm when the temperature was increased. Moreover, all the samples are photoelectrically active under simulated solar light. High sensitivity and enhanced photocurrent bring a profound understanding to photoswitches and photodetectors using GZO nanostructures.