Investigation of hybrid CuPc-doped ZnO/p-silicon photodiodes for photonic and electronic applications

Abstract

Copper phthalocyanine (CuPc) doped zinc oxide (ZnO) interlayered Al/p-Si Schottky barrier diodes (SBDs) were systematically fabricated utilizing spin coating technique. This study was undertaken to meticulously assess the influence of varying concentrations of CuPc on the intricate electrical and photodiode characteristics of these devices. The investigation involved the characterization of the current–voltage (I–V) characteristics configured with distinct different doping concentrations of CuPc such as 0.05 wt%,1 wt%, 2 wt%, under a wide range of voltages (± 5 V) and illumination irradiances. These measurements enabled the calculation of various critical electrical variables, such as the ideality factor (n), barrier height (ΦB), series resistance (Rs), shunt resistance (Rsh), interface states density (Nss) and their response under various illumination levels (between 10 and 100 mW/cm2) and under dark condition. An increase in the reverse current as the illumination increases suggested the potential utility of these SBDs as photodiodes, photosensors, or photodetectors. Notably, the linear dynamic range (LDR), a crucial factor for image sensors which obtained around 14 for all photodiodes. The photodiodes exhibited a good rectification ratio (RR) of approximately 104. The results obtained indicate that the rectifying properties of the structures can be controlled by CuPc doping. In addition, the results indicated that the presence of CuPc significantly influenced the values of n, ΦB, Rs/Rsh, and Nss. To further analyze the devices, capacitance–voltage (C–V) and conductance–voltage (G–V) measurements were carried out to determine parameters such as diffusion potential (VD), dopant acceptor atoms concentration (NA), Fermi energy level (EF), and width of depletion layer (WD) at both 1 kHz and 1 MHz. The measurements revealed that the capacitance values were higher at low frequencies compared to high frequencies, and this behavior was attributed to Nss. In summary, this study suggests that the manufactured photodiodes have the potential to be employed as photodiodes, sensors, or detectors in optical sensing applications, and their performance can be tailored by adjusting the concentration of CuPc in the ZnO interlayered structures. The discerned outcomes revealed the substantial influence of CuPc concentration on key electrical parameters, with conspicuous trends noted in the values of n, ΦB, Rs/Rsh, and Nss. Furthermore, the observed increase in the reverse current as the illumination level increases highlights the potential utility of these SBDs as sensitive photodiodes/sensors/detectors.