Molybdenum oxide (MoO3) offers pivotal advantages for high optical transparency and low light reflection. Considering device fabrication, n-type MoO3 semiconductor can spontaneously establish a junction with p-type Si. Since the energy bandgap of Si is 1.12 eV, a maximum photon wavelength of around 1,100 nm is required to initiate effective photoelectric reaction. However, the utilization of infrared photons is very limited for Si photonics. Hence, to enhance the Si photoelectric devices, we applied the wide energy bandgap MoO3 (3.7 eV) top-layer onto Si. Using a large-scale production method, a wafer-scale MoO3 device was fabricated with a highly crystalline structure. The MoO3/p-Si heterojunction device provides distinct photoresponses for long wavelength photons at 900 nm and 1,100 nm with extremely fast response times: rise time of 65.69 ms and fall time of 71.82 ms. We demonstrate the high-performing MoO3/p-Si infrared photodetector and provide a design scheme for the extension of Si for the utilization of long-wavelength light.
