Fig. 3: BP in-plane PN homojunction photodetector with ultrahigh polarization sensitivity.
a Schematic of BP in-plane PN homojunction defined by ferroelectric domains. b High-resolution transmission electron microscopy (HR-TEM) image and energy-dispersive X-ray spectroscopy (EDS) elemental mapping of F, P and Si. The inset is the partial enlarged drawing HR-TEM image and the thickness of BP is 4.8 nm. Scale bar is 5 μm. c The PFM phase image of the device. The phase difference between p-doped (P) region and n-doped (N) region is 180°. The inset shows corresponding optical image. The black dashed lines indicate the electrodes, the red dashed lines indicate the edge of BP material and the white dashed lines indicate the boundary of P and N region. Scale bar is 5 μm. d Isd–Vsd curves in the dark and under light of different incident polarization angle (λ = 1450 nm, Peff = 10 μW). e Normalized photocurrent of the BP in-plane PN homojunction as a function of the polarization angle. The unity corresponds to photocurrent when angle is 90° or 270° at 520 nm (10 μW) and 1450 nm (10 μW). Polarizatio ratio (PR) is defined as the ratio of maximum and minimum polarization-dependent photoresponse. f the spatial photocurrent map is obtained by scanning a 520 nm light beam with power 1 μW and spot size 1 μm. Scale bar is 5 μm.
