Three-dimensional Dirac semimetal (Cd 1− x Zn x ) 3 As 2 /Sb 2 Se 3 back-to-back heterojunction for fast-response broadband photodetector with ultrahigh signal-to-noise ratio

Three-dimensional (3D) Dirac semimetal materials have great application prospects in broad-spectrum photodetectors (PDs) working at wavebands up to the mid/far infrared region owing to their unique topological energy-band architectures and excellent photoelectric properties. However, the relatively high dark current in most Dirac semimetal-based PDs limits their photodetection performance, with poor signal-to-noise ratios (SNRs). Herein, we developed an ultra-low-noise-level PD linear array based on a 3D Dirac semimetal (Cd 1− x Zn x ) 3 As 2 /Sb 2 Se 3 back-to-back (BTB) heterojunction using a molecular beam epitaxy (MBE)-grown (Cd 1− x Zn x ) 3 As 2 film. Benefiting from the effective double-heterojunction design strategy, the as-fabricated (Cd 1− x Zn x ) 3 As 2 /Sb 2 Se 3 linear-array PD exhibited an outstanding photodetection capacity from the visible to mid-infrared region (450 nm to 4.5 µm), with the highest recorded SNR close to 10 4 , excellent peak specific detectivity of 5.2 × 10 12 Jones, and high response speed of about 87.5 µs at room temperature. Furthermore, the PD exhibited long-term stability and uniformity as only minor photocurrent fluctuations occurred among different PD linear-array units demonstrating the feasibility of the PD for advanced optoelectronic applications, such as real-time light trajectory tracking. This work provides a reference strategy for the fabrication of fast-response broadband PDs with ultrahigh SNRs using the 3D Dirac semimetal (Cd 1− x Zn x ) 3 As 2 /Sb 2 Se 3 BTB heterojunction and demonstrates the great prospect of 3D Dirac semimetal materials for the manufacture of fast-response uncooled focal-plane-array devices.