Selenization Growth Mechanism of PdSe ₂ Nanoscale-Thick Films in Large-Diameter Quartz Tube and PdSe ₂ /Si 2D-3D PIN-like Photodetectors

In this study, we innovatively discovered the influence of Se vapor concentration on film formation during selenization via the TAC method, revealing the quantitative regulation mechanism of Se vapor concentration within large-diameter quartz tubes on the growth mode of PdSe 2 nanoscale-thick films. It is found that at lower Se concentrations, the PdSe 2 nanoscale-thick films exhibit larger grains and island-like growth with a dispersed distribution, while at higher Se concentrations, the PdSe 2 nanoscale-thick films display smaller grains with a continuous and dense stacking arrangement, confirming that a Se-rich environment significantly improves the crystallinity of the films. Based on this, a vertical PdSe 2 /n – -Si/n + -Si 2D–3D PIN-like photodetector is constructed. The device, with a 500 nm intrinsic layer, demonstrates a comprehensive performance improvement over a 5 μm thick layer device. The device exhibits excellent performance across a wide spectral range of 532–2200 nm: a responsivity of 202 nA/W at 1310 nm (+22.3%), a responsivity of 17.4 nA/W at 1550 nm (+168%), a long-wavelength response at 2200 nm, an extended linear dynamic range from 46 to 76 dB (+65%), dark current suppression from 1 nA to 10 pA (2-order-of-magnitude reduction), and a specific detectivity increase from 2.1 × 10 10 Jones to 5.82 × 10 10 Jones (+177%). The rise/fall time is reduced from 739 μs/3.64 ms to 250 μs/1.5 ms (speedup by 3–4 times), and the 3 dB bandwidth is expanded from 238 Hz to 3.35 kHz (+14 times). Furthermore, room-temperature infrared imaging at 1310 nm is successfully achieved. This work establishes a “mechanism innovation-structure design-performance comparison” research paradigm for 2D material optoelectronic devices.