Scalable MBE growth of MoSe2/GaTe van der Waals heterostructure for high-speed vis-NIR photodetection†

Two-dimensional (2D) material-based photodetectors have gained significant attention in recent years due to their ultrafast response times and tunable optoelectronic properties. As the demand for photodetectors with enhanced responsivity across different wavelengths increases, 2D/2D heterostructures have become a key focus for overcoming the limitations of traditional metal–semiconductor–metal (MSM) photodetectors. In this work, we report a high-performance visible-near-infrared (NIR) photodetector based on a MoSe₂/GaTe heterostructure grown using a molecular beam epitaxy (MBE) system on a SiO₂/Si substrate. The heterostructure exhibits a type-III (broken-gap) band alignment, facilitating efficient charge separation and enabling higher responsivity across ultraviolet (UV), visible, and NIR wavelengths compared to the MSM-GaTe-based device. The photodetector achieves the highest responsivity of 0.6 A W⁻¹ at 200 nm in the UV region while demonstrating fast response times of 44 ms (rise) and 67 ms (decay) under 780 nm visible illumination. In the NIR range (1000 nm), response times extend to 242 ms (rise) and 340 ms (decay), maintaining strong photodetection capability. The transient current spikes observed under 780 nm illumination arise from the pyroelectric effect, attributed to GaTe's non-centrosymmetric nature, highlighting the interplay of thermal and photoelectric contributions. This unique combination of features makes the MoSe₂/GaTe heterostructure an attractive candidate for advanced photodetection applications in the visible and NIR wavelength ranges.