Effect of Co and Ni on Au/Zn_1-xM_xO Nanorods (M = Co and Ni) Schottky Photodiodes Performance

Au/Zn_1-xM_xO nanorods (M = Co and Ni) Schottky photodiodes were fabricated on p-Si substrate. The surface morphology, structural, vibrational, electrical and capacitive properties were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, current-voltage (I-V), capacitance-voltage (C-V), and ultraviolet (UV)-illumination measurements. FE-SEM and XRD results show that NR arrays are well distributed, orthogonal to the substrate, and highly oriented along the preferential (002) plane. Distinct peaks of Co and Ni were found in their respective energy dispersive X-ray (EDX) spectrum. An intrinsic characteristic peak was found to be ∼437 cm^-1 in the Raman spectra which indicates the good crystallinity of Zn_1-xM_xO NRs. The Schottky photodiodes show good rectifying property in dark condition and the ideality factor to be greater than unity. However, the barrier height was increased attributed to an increase of band gap due to the Burstein-Moss effect, density of interface states, and barrier inhomogeneities. The obtained barrier height was found to be 0.52, 0.54, and 0.53 eV (from I-V measurements) and 0.70, 0.78, and 0.73 eV from C-V measurements, respectively. The carrier density and the responsivity were higher for doped samples than undoped NR arrays suggesting the incorporation of Co and Ni into the ZnO lattice.