Self-powered visible-UV light photodiodes based on ZnO nanorods-silicon heterojunctions with surface modification and structural enhancement

Abstract

The letter reports the visible-UV light response of Al/ZnONRs/ZnOseed/p-Si/Al type photodiodes (PDs) with surface modification and structural enhancement. The PDs, which are referred to as PD10–2, PD10–4, PD20–2, PD20–3, and PD20–4 according to molar concentration (mM) and time (hour), were produced for improving the performances. Basic electronic parameters were obtained from the I-V data of Al/ZnONRs/ZnOseed/p-Si/Al type PDs by using thermionic emission (TE) theory, Ohm's law, and Cheung's methods. In accordance with the literature, the results showed that the potential barrier height (ФBo) values decreased with the increasing illumination intensity, while the ideality factor (n) values increased. In addition, voltage-dependent series resistance (Rs) values of the PDs under dark and different visible-UV light intensities were calculated by using Ohm's law and Cheung's method. It was observed that the Rs values decreased with increasing light intensities. On the other hand, the photosensitivity characteristics of the PDs at visible-UV light intensities were investigated depending on the applied voltage. While the photosensitivity value of the produced PD10–2 device reached the maximum value of 6.9 × 103 at the short-circuit voltage Vsc= 0 V, the open-circuit voltage Voc showed better photosensitivity with a minimum value of 0.0702 in the self-powered mode. In addition, the responsivity (R) and the detectivity (D*) values of Al/ZnONRs/ZnOseed/p-Si/Al type PDs were calculated. Herein, the R and D* values decreased with increasing power density at zero-bias voltage in accordance with the literature. Also, the R and D* values of the PD10–2 device are higher and lower than other devices, respectively. The linear dynamic range (LDR) value of the PD10–2 device reaches ~78 dB with a maximum value at Vbias= 0 V, while the dark current is 0.21 nA with a minimum value, self-powered mode. It is concluded that the PD10–2 device is suitable for photodiode applications in self-powered mode.