Properties and photodetector applications of two-dimensional black arsenic phosphorus and black phosphorus

Two-dimensional (2D) black arsenic phosphorus (b-AsP), as an alloy of black phosphorus (b-P) with arsenic, has attracted great attention because of its outstanding electronic and optical properties, including high carrier mobility, tunable bandgap and in-plane anisotropy. B-AsP has a smaller bandgap (0.15–0.3 eV) than the b-P bandgap (0.3–2.0 eV), and thus can be used for mid-infrared photodetectors. In addition, both of them can form various van der Waals (vdW) heterojunctions with other 2D materials to realize novel functional optoelectronic devices. Here, we compare the basic characteristics of b-AsP and b-P, including crystal structure, optical properties, band structure, electrical properties and stability, and we summarize the update progress of b-AsP in photo detection, including representatives of phototransistor and photodiode devices. In the last part, the future research directions are discussed.