Black phosphorus and its isoelectronic materials

The family of 2D and layered materials has been expanding rapidly for more than a decade. Within this large family of hundreds of materials, black phosphorus and its isoelectronic group IV monochalcogenides have a unique place. These puckered materials have distinctive crystalline symmetries and exhibit various exciting properties, such as high carrier mobility, strong infrared responsivity, widely tunable bandgap, in-plane anisotropy and spontaneous electric polarization. Here, we review their basic properties, highlight new electronic and photonic device concepts and novel physical phenomena and discuss future directions. Layered black phosphorus and its isoelectronic group IV monochalcogenides have distinctive physical properties arising from their unusual crystal symmetries. This Review discusses some of the interesting physical phenomena, possible device applications and future research directions for this group of materials.