Theoretical study of strained black phosphorus photodetector integrated with silicon waveguide

We compare optical characteristics of black phosphorus photodetectors integrated with a stripe waveguide and a ridge waveguide by optical field intensity and absorption spectrum, which proves that the stripe waveguide is better for enhancing the optical absorption of black phosphorus photodetector. The strain effect on the band structure of black phosphorus is investigated using the first-principles method based on density functional theory (DFT). The band structure of 5-layer BP experiences a direct-indirect-direct transition and a semiconductor-metal transition (SMT) when applied different strains. As a result, the cut-off wavelength and the responsivity of this strained BP photodetector can reach 3.76 μm and 0.48 A/W respectively. In a word, the waveguide-integrated black phosphorus photodetector under strain for mid-infrared range may promote potential novel optoelectronic device applications based on two-dimensional materials in the future.