Fig. 2: Polarization photoelectric performance of b-As_0.2P_0.8 phototransistor.

a Schematic structure of the b-As_0.2P_0.8 polarization phototransistor. b Cross-sectional TEM image and the high-angle annular dark field (HAADF) of the device fabricated on a SiO₂/Si substrate, and the element distributions. c Output characteristic I_ph-V_ds curves under 1550 nm laser irradiation at different powers, with the inset depicting the transfer curves under dark and illumination at fixed V_ds = 0.1 V. d Anisotropic total current of the device under linearly polarized 1550 nm laser illumination. e The anisotropic response of the net photocurrent as incident power (P_in from 0.03 to 382 μW) demonstrates a stable anisotropic behavior. f The polar plot showing angle-resolved photocurrent for the V_g of −60, 0, and 60 V, revealing periodic variations consistent with the inherent anisotropy. g The polar plot shows the angle-resolved photocurrent for V_ds ranging from 0.02 V to 0.1 V. h Spatial mapping of the photocurrent across the b-As_0.2P_0.8 phototransistor under different polarization orientations of the incident laser, recorded at V_ds = 0.1 V and V_g = 60 V. The photocurrent reaches a maximum when the light polarization is aligned at 0° and a minimum at 90°, emphasizing the polarization sensitivity of the device. i Comparison of the photocurrent anisotropic ratio and photoresponse range of the b-As_0.2P_0.8 phototransistor against those of other widely used 2D and 1D materials^14,46,47,48