High-performance mid-infrared photodetection based on Bi₂Se₃ maze and free-standing nanoplates

The pursuit of optoelectronic devices operating in mid-infrared regime is driven by both fundamental interests and commercial applications. The narrow bandgap (0.3 eV) of layered Bi₂Se₃ makes it a promising material for mid-infrared photodetection. However, the weak absorption of mid-infrared optical power and high dark current level restrict its performance. Here, a supply-control technique is applied to modulate the growth mode of Bi₂Se₃ crystal, and Bi₂Se₃ crystals with various morphologies are obtained. The nanoplates pattern transits from maze to freestanding when source mass was tuned. Due to the strong infrared absorption and photoelectric conversion efficiency of vertical Bi₂Se₃ nanoplates, the as-prepared vertical Bi₂Se₃ nanoplates/Si heterojunction shows excellent photoresponse and extremely low dark current. Among these devices based on different Bi₂Se₃ morphologies, freestanding nanoplates show the optimal mid-infrared characteristics, namely a photo-to-dark ratio of 2.0 × 10⁴, a dark current of 0.21 pA, a response time of 23 ms, a specific detectivity of 6.1 × 10¹⁰ Jones (calculated) and 1.2 × 10¹⁰ Jones (measured) under 2.7 μm illumination and at room temperature. Notably, the specific detectivity of our devices are comparable to commercial InGaAs photodetectors. With the tunable- morphology growing technique and excellent photoresponding characteristics, Bi₂Se₃ nanomaterials are worth attention in optoelectronic field. (paper)