Enhanced Spectral Response of ZnO-Nanorod-Array-Based Ultraviolet Photodetectors by Alloying Non-Isovalent Cu–O with CuAlO2 P-Type Layer

Abstract

CuAlO2 was synthesized by a hydrothermal method, in which the Cu–O dimers were incorporated by simply altering the ratio of the reactants and the temperature. The incorporation process increases the grain size in CuAlO2, and modulates the work function and binding energies for CuAlO2 due to the partial substitution of Cu+ 3d10 with Cu2+ 3d9 orbitals in the valence band maximum by alloying non-isovalent Cu–O with a CuAlO2 host. Based on the ZnO nanorod arrays (NRs) ultraviolet photodetector, CuAlO2/Cu–O fabricated by the low-cost drop-coating method was used as the p-type hole transport layer. The incorporation of the Cu–O clusters into CuAlO2 lattice to enhance the conductivity of CuAlO2 is an effective way for improving ZnO NRs/CuAlO2 device performance. The photodetectors exhibit significant diode behavior, with a rectification ratio approaching 30 at ±1 V, and a dark saturation current density 0.81 mA cm−2. The responsivity of the ZnO-NRs-based UV photodetector increases from 13.2 to 91.3 mA/W at 0 V bias, with an increase in the detectivity from 2.35 × 1010 to 1.71 × 1011 Jones. Furthermore, the ZnO NRs/[CuAlO2/Cu–O] photodetector exhibits a maximum responsivity of 5002 mA/W at 1.5 V bias under 375 nm UV illumination.