Self‐Powered Photodetector Based on p‐Type CuBi2O4 with Fermi Level Engineering

Abstract

AbstractSi‐based photodetectors (PDs) have been widely used in human‐machine interaction systems due to their robust optoelectronic properties despite limitations of significant large leakage current. To overcome this drawback, a functional overlayer of p‐type CuBi2O4 (CBO) is deposited on the surface of n‐type Si to build a novel photodetector involving a p–n heterojunction. Such an n‐Si/p‐CBO photodetector shows an ultralow dark current ≈10−11 A with a high photosensitivity up to 1.69 × 104 at zero bias, a strong self‐powered characteristics with a photovoltage near 0.55 V, and a fast rise and decay time around 0.1 and 0.3 ms. With these advantages, the device shows great performance in the optical communication system. The thickness‐dependent performance indicates that the top layer acts as a light‐harvesting semiconductor to generate, separate, and transport photocarriers through the built‐in heterojunction. Band alignment analysis confirms this result and reveals the formation of a type‐II heterojunction at the interface of n‐Si and p‐CBO layers. This work demonstrates an effective strategy to reduce the leakage current and improves the responsivity, detectivity, and response speed of Si‐based self‐powered photodetectors.