High rectification and gate-tunable photoresponse in 1D-2D lateral van der waals heterojunctions

The self-passivating surfaces and reduced tunneling leakage current enable the creation of ideal Schottky contacts in van der Waals (vdW) semiconductor heterojunctions. However, simultaneously achieving high rectification ratios, low reverse leakage currents, and rapid photoresponse remains challenging. Here, we present a one-dimensional (1D)/two-dimensional (2D) mixed-dimensional heterostructure photodiode to address these challenges. The significant valence band offset and minimal electron affinity difference in this structure ensure high rectification ratios and efficient charge collection. Additionally, the dimensional disparity between the 1D and 2D materials, characterized by a smaller contact area and significant thickness difference, results in low reverse leakage current and a high current on-off ratio. Moreover, it enables gate-tunable band structure transitions. Our device exhibits an exceptional rectifying ratio of 4.7 × 107 and a high on-off ratio of 5 × 107 (Vds = 2 V and, Vg = 30 V) at room temperature. Under a gate voltage of 20 V, the photodiode achieves a specific detectivity (D*) of 4.9 × 1014 Jones, a rapid response time of 14 μs, and an extended operational wavelength approaching to 1550 nm. The strategic combination of mixed-dimensional design and band engineering yields a 1D-2D p-n heterojunction photodiode with remarkable sensitivity, repeatability, and fast response, underscoring the potential of vdW semiconductors for advanced optoelectronic applications.