Enhanced Spectral Response of ZnO-Nanorod-Array-Based Ultraviolet Photodetectors by Alloying Non-Isovalent Cu–O with CuAlO(2) P-Type Layer

CuAlO(2) 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 CuAlO(2), and modulates the work function and binding energies for CuAlO(2) due to the partial substitution of Cu(+) 3d(10) with Cu(2+) 3d(9) orbitals in the valence band maximum by alloying non-isovalent Cu–O with a CuAlO(2) host. Based on the ZnO nanorod arrays (NRs) ultraviolet photodetector, CuAlO(2)/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 CuAlO(2) lattice to enhance the conductivity of CuAlO(2) is an effective way for improving ZnO NRs/CuAlO(2) 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 × 10(10) to 1.71 × 10(11) Jones. Furthermore, the ZnO NRs/[CuAlO(2)/Cu–O] photodetector exhibits a maximum responsivity of 5002 mA/W at 1.5 V bias under 375 nm UV illumination.