n-ZnO/p-Si photodiodes fully isolated by B+ ion-implantation

Abstract We report on the fabrication of a heterojunction photodiode for the visible range that consists of a transparent insulating ZnO (i-ZnO) overlayer and a transparent semiconducting n-ZnO layer on p-Si. For device isolation, we implanted B + ions into peripheral n-ZnO layer with varying doses and found considerable reduction of dark leakage current in our device at a low-dose of 5 × 10 13 cm −2 . We have also obtained wide-range spectral quantum efficiency for our isolated photodiodes. They exhibited quite a high-quantum efficiency of 45% under 700 nm (red) photons but the efficiency drops at 380 nm near ultraviolet (UV) because the top insulating i-ZnO layers absorbed most of the UV photons with higher energy than ZnO band gap (3.3 eV, ∼380 nm) before they would reach n-ZnO/p-Si region.