Strong Anisotropic Two-Dimensional In2Se3 for Light Intensity and Polarization Dual-Mode High-Performance Detection

Detecting the light from different freedom is of great significance to gain more information. Two-dimensional (2D) materials with low intrinsic carrier concentration and highly tunable electronic structure have been considered as the promising candidate for future room-temperature multi-functional photo-detectors. However, current investigations mainly focus on intensity-sensitive detection; the multi-dimensional photodetection such as polarization-sensitive photodetection is still in its early stage. Herein, the intensity-and polarization-sensitive photo-detection based on alpha-In2Se3 is studied. By using angle-resolved polarized Raman spectroscopy, it is demonstrated that alpha-In2Se3 shows an anisotropic phonon vibration property indicating its asymmetric structure. The alpha-In2Se3-based photodetector has a photoelectric performance with a responsivity of 1936 A/W and a specific detectivity of 2.1 x 1013 Jones under 0.2 mW/cm2 power density at 400 nm. Moreover, by studying the polarized angle-resolved photoelectrical effect, it is found that the ratio of maximum and minimum photocurrent (dichroic ratio) reaches 1.47 at 650 nm suggesting good polarization-sensitive detection. After post-annealing, alpha-In2Se3 in situ converts to beta-In2Se3 which has similar in-plane anisotropic crystallinity and exhibits a dichroic ratio of 1.41. It is found that the responsivity of beta-In2Se3 is 6 A/W, much lower than that of alpha-In2Se3. The high-performance light intensity-and polarization-detection of alpha-In2Se3 enlarges the 2D anisotropic materials family and provides new opportunities for future dual-mode photodetection.