Ultrafast High-Photogain UV–Vis-NIR Broadband Photodetection in Parallelly Overlapped Stacking Type-I GaSe/MoTe2 Heterostructure

Broadband photodetectors are important for next-generation optoelectronic applications, ranging from fundamental science, environmental monitoring, industrial detection to artificial-intelligence-enabled Internet of Things systems, where both high responsivity and fast response are critically demanded. Typically, a trade-off exists between the two in the photogating effect, making it challenging to achieve both simultaneously. This study reports a parallelly overlapped stacking GaSe/MoTe2 heterostructure with type-I band alignment (PSH-GM), which simultaneously realizes an ultrafast photoresponse of 523 ns and a high responsivity of 8.95 × 103 A·W–1, together with a noise equivalent power of ∼0.38 × 10–14 W·Hz–1/2 and a specific detectivity of 8.01 × 1011 Jones. Furthermore, PSH-GM exhibits a responsivity of up to 103 A·W–1 over a broad spectral range of 355–1100 nm, covering the ultraviolet (UV), visible (Vis), and near-infrared (NIR) regions. The underlying photodetection mechanism of the parallelly overlapped stacking type-I heterostructure is clarified using photocurrent mapping, and the origin of the dark current shift at different operation frequencies is elucidated, both of which offer insights into the design principles of two-dimensional heterostructures optimized to simultaneously achieve high responsivity and high response bandwidth. Imaging demonstrations are conducted at 355, 520, and 850 nm, and free-space optical communication is demonstrated at 115.2 kbit·s–1, which highlights the potential of PSH-GM for broadband UV–Vis–NIR photodetection, ultrafast data communication, high-speed imaging, and integration into advanced optoelectronic systems.