Nanoscale InSe/GaTe van der Waals Heterojunction Diodes for Extreme Deep Ultraviolet Detection in Semiconductor Lithography and Inspection

Multilayer van der Waals (vdW) transition metal chalcogenides (TMCs) with nanoscale thickness have garnered attention for high-speed optoelectronic applications. However, conventional TMC-based photodetectors often suffer from high dark current and require substantial external bias due to limited light absorption and inefficient carrier separation. In this work, we present a high-performance broadband photodetector based on a vertical vdW heterostructure (vdWH) composed of nanoscale exfoliated InSe (∼58 nm) and molecular beam epitaxy (MBE)-grown ultrathin GaTe (∼5 nm). This layered stack leverages type-II band alignment and the quantum-confined nature of the individual layers to facilitate efficient charge separation and reduced dark current. The InSe/GaTe vdWH demonstrates outstanding broadband responsivity spanning 200–1100 nm, with exceptional performance in the extreme deep UV region. Peak responsivity values of 154.37 A/W at 200 nm, 2.21 A/W at 690 nm, and 1.10 A/W at 890 nm are observed at −5 V, matching well with the bandgaps of InSe (1.4 eV) and GaTe (1.67 eV). These nanoscale-engineered layers yield enhanced light–matter interaction, contributing to a detectivity of 4.43 × 1012 Jones and noise equivalent power (NEP) of 8.89 × 10–16 W/Hz1/2 at 200 nm. Notably, the photodetector exhibits a rapid rise time of 8 ms at 200 nm, underscoring its capacity for high-speed detection. These nanoscale-engineered 2D layers not only enhance light–matter interaction but also enable fast, low-noise operation under extreme DUV conditions. Such characteristics make the device a promising candidate for semiconductor process monitoring, particularly deep-ultraviolet (DUV) lithography exposure control, wafer inspection, and contamination detection in next-generation chip fabrication and nanomanufacturing environments.