Defect-Mediated Transport in Self-Powered, Broadband, and Ultrafast Photoresponse of a MoS₂/AlN/Si-Based Photodetector

By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here, we report a self-powered and ultrafast photodetector based on a hybrid MoS2/AlN/Si heterostructure. The heterojunction is formed by depositing a MoS2 thin film by pulsed laser deposition on an AlN/Si(111) template. The vertical transport properties of the device under dark and light illumination conditions exhibit an excellent photoresponse in a broad range of wavelengths (300–1100 nm) at 0 V. The maximum responsivity of this photodetector is found to be 9.93 A/W at a wavelength of 900 nm. The device shows an ultrafast temporal response with response/recovery times of 12.5/14.9 μs. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy reveal the presence of native oxygen impurities in AlN throughout the bulk of the film. These oxygen defects form a deep donor level in AlN and play a crucial role in the transport of the photogenerated carriers, resulting in enhanced device performance.