Breaking the Cut-Off Wavelength Limit of GaTe through Self-Driven Oxygen Intercalation in Air.

Low symmetric two dimensional (2D) semiconductors are of great significance for their potential applications in polarization-sensitive photodetection and quantum information devices. However, their real applications are limited by their photo-detecting wavelength ranges, which are restricted by their fundamental optical bandgaps. Recently, intercalation has been demonstrated to be a powerful strategy to modulate the optical bandgaps of 2D semiconductors. Here, the authors report the self-driven oxygen (O 2 ) intercalation induced bandgap reduction from 1.75 to 1.19 eV in gallium telluride (GaTe) in air. This bandgap shrinkage provides the long-wavelength detection threshold above ≈1100 nm for O 2 intercalated GaTe (referred to as GaTeO 2 ), well beyond the cut-off wavelength at ≈708 nm for pristine GaTe. The GaTeO 2 photodetectors have a high photoresponsivity, and highly anisotropic photodetection behavior to even sub-waveband radiation. The dichroic ratio (I max /I min ) of photocurrent is about 1.39 and 2.9 for 600 nm and 1100 nm, respectively. This findings demonstrates a broadband photodetector utilizing GaTe after breaking through its bandgap limitation by self-driven O 2 intercalation in air and further reveal its photoconductivity anisotropic nature. This provides design strategies of 2D materials-based high-performance broadband photodetectors for the exploration of polarized state information.