Abstract
A lateral phototransistor structure based on mechanically exfoliated multilayer black arsenic (b-As) is produced to test its in-plane anisotropy of photoelectrical properties. First, the morphology and structure of the b-As flake are investigated with respect to light polarization and crystal structure orientation. Then, the Raman modes, demonstrating a strong anisotropic nature of twofold symmetry for in-plane vibrations and fourfold symmetry for out-of-plane vibrations, allow us to define the armchair and zigzag crystal directions. The lateral photodetector structure has been prepared by depositing polar-oriented electrodes with an angular step of 45 degrees correlated along the b-As crystal directions. Angle-resolved electrical transport and polarization resolved photocurrent measurements show its strong in-plane anisotropic photoelectrical properties when conductance and photocurrent are about 2 times higher across the armchair direction than the zigzag one. The respective photoresponsivity at 980 nm is 0.44 and 0.19 A/W with the dichroic ratio of 2.3. The intrinsic linear dichroism conversion is responsible for the unique orientation selection behavior in polarization-dependent photodetection. The results show that multilayer b-As is a potentially useful material for application in innovative polarization-sensitive photodetectors.