Black Phosphorus Based Photodetectors

The layered two-dimensional (2D) black phosphorus (BP) has found significant applications in nanoelectronics and nanophotonics. In particular, it has been proven as a promising material for photodetectors due to its narrow direct bandgap ranging from 0.3 eV to 2 eV, high carrier mobility, modulation capability, and polarization sensitivy. The modulation capability of BP based photodetector is achieved by gate control using field effect transistor structure. Homojunction and heterojunction have been demonstrated to suppress dark current while enhancing carrier collection efficiency. Plasmonic effect and avalanche breakdown are exploited to boost the responsivity further. To extend the detection wavelength of BP, electric field modulation and arsenide doping are investigated, leading to a wide detection wavelength up to 8 µm. Owing to the ease of integrating BP with diverse substrates due to BP's 2D nature, waveguide-integrated BP based photodetectors are realized in the near-infrared (NIR) for telecommnunication applications and in the mid-infrared (MIR) for on-chip sensing applications. High speed and high responsivity can be achieved by optimizing the device design. Despite that the mechanical robustness of BP on waveguide remains challenging, nevertheless, wafer-level growth of BP is highly desirable to realize scalable integration for mass production.