Spectral responsivity and quantum efficiency of n-ZnO/p-Si photodiode fully isolated by ion-beam treatment

We report on the fabrication of a heterojunction photodiode for the visible range that consists of a transparent insulating ZnO overlayer and a transparent semiconducting $\mathrm{n-}\mathrm{ZnO}$ layer on $\mathrm{p-}\mathrm{Si}.$ For device isolation, we implanted ${\mathrm{Si}}^{+}$ ions into the $\mathrm{n-}\mathrm{ZnO}$ layer. We have obtained a wide-range spectral responsivity curve for our isolated photodiodes, which showed a maximum quantum efficiency of 70% at 650 nm and a minimum of 10% at 420 nm. However, they exhibited an efficiency drop at 380 nm in the near-ultraviolet because the ZnO layers absorbed the photons of higher energy before they reached $\mathrm{p-}\mathrm{Si}.$ The ion-beam-induced isolation considerably reduced dark leakage currents in our devices when the dose of Si ions was as high as ${\text{5×10}}^{15}\hspace{0.5em}{\mathrm{cm}}^{\text{−2}}.$