Low-voltage, self-powered and broadband photodetector with Ohmic, transparent and cost-effective AZO electrodes on vertical aligned MoS2 flakes

The transparent Ohmic electrodes are the extreme necessity to develop cutting-edge broadband photodetectors. Conventional metal electrodes reflect incident light and diminish overall performance of photodetector. Here, we report cost-effective, transparent Ohmic Al-doped ZnO (AZO) electrodes to develop self-powered, highly responsive photodetectors from visible to near-infrared regions using vertically-aligned MoS2 (VA- MoS2) flakes. The MoS2 photodetector with AZO electrode (AZO-MoS2) shows a high responsivity of 40.67 A/W at 800 nm at low biasing voltage of 0.5 V. The self-driven behavior is observed in a broad range from 400 to 1100 nm with high responsivity of 38.18 mA/W at 800 nm. Moreover, AZO-MoS2 device has fast rise and decay time. To understand impact of Ohmic AZO electrode in comparison to traditional metal electrodes, we have also investigated conventional Au-MoS2 PDs fabricated under identical dimensions. The AZO-MoS2 PD demonstrated 100 times higher responsivity than conventional Au-MoS2 PD at 800 nm. We have investigated band-alignment between AZO and MoS2 using ultraviolet spectroscopy (UPS) and confirmed ohmic nature between the AZO and MoS2. These results indicate superior performance of AZO-MoS2 PD device in comparison to traditional metal electrodes.