Enhanced self-powered ultraviolet photoresponse of ZnO nanowires/p-Si heterojunction by selective in-situ Ga doping

In the current work, Ga-doped ZnO nanowires are grown by employing double step chemical bath deposition (CBD) method on Si substrate for fabricating the n-Ga:ZnO nanowires/p-Si heterojunction photodiodes. The doping concentrations have been systematically varied (1%-5%) for obtaining superior photo-responsive properties. The morphology, chemical composition and crystalline nature of the grown nanowires are studied by using FESEM, EDS and XRD, respectively. The vacancies/defect states and energy bandgap are studied from CL and UV-vis spectra. The photo-electric measurements indicate that optimized Ga-doped ZnO nanowires/p-Si heterojunction provides enhanced performance in terms of photo-to-dark current ratio (>2 x of undoped), response time, responsivity (0.192 A/W) and EQE (62.7%) in self-powered mode. At zero bias, 16.6% enhancement in responsivity has been observed for optimized Ga-doped ZnO nanowires/p-Si heterojunction as compared to undoped one with a highly selective UV-A (320 nm-400 nm) spectrum.