Tri-layered Si/Co3O4/ZnO heterojunction for high-performance visible photodetection

Abstract

Tri-layered heterojunction devices based on oxide thin films are attracting significant attention for ultra-fast visible photodetection. However, the responsivity of these devices is still low. In this work, high performance photodetectors based on a tri-layered heterojunction of n-Si/p-Co₃O₄/n-ZnO were fabricated. Under no applied bias, a maximum responsivity and detectivity of 14.2 mA W⁻¹ and 1.34 × 10¹² Jones were achieved respectively, for a power density of 9.35 mW cm⁻². Remarkably, a significant increase in the responsivity of approximately 864% was found when the device was biased at −2 V. This effect is understood based on the coupling of the photovoltaic and pyroelectric effects. Also, upon applying an external bias of −2 V, at a laser power density of 9.35 mW cm⁻² and at a chopper frequency of 10 Hz, the device exhibits a detectivity and sensitivity of 3.4 × 10¹¹ Jones and 2.2, respectively, together with a rise and fall time of 4 and 2 μs, respectively. Compared to high performance Al/Si/SnO/ZnO/ITO and Au/pCuI/ZnO devices, our voltage-biased Al/Si/Co₃O₄/ZnO/ITO devices exhibit a >40% increase in R and >10× higher D*. Furthermore, an important advantage of our PDs is the p-type component, Co₃O₄, which is more stable and stoichiometric than CuI and SnO, ensuring PD performance that is stable with time. Therefore, n-Si/p-Co₃O₄/n-ZnO heterojunction devices shows great promise for ultrafast visible photodetection.