High-performance mid-infrared photodetection based on BiSe 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 BiSe 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 BiSe crystal, and BiSe 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 BiSe nanoplates, the as-prepared vertical BiSe nanoplates/Si heterojunction shows excellent photoresponse and extremely low dark current. Among these devices based on different BiSe morphologies, freestanding nanoplates show the optimal mid-infrared characteristics, namely a photo-to-dark ratio of 2.0 × 10, a dark current of 0.21 pA, a response time of 23 ms, a specific detectivity of 6.1 × 10 Jones (calculated) and 1.2 × 10 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, BiSe nanomaterials are worth attention in optoelectronic field.