Self-powered AlGaN-based MSM solar-blind ultraviolet photodetectors with high Al-content Al_xGa_1-xN/Al_yGa_1-yN asymmetrical heterostructure

An Al0.4Ga0.6N-based metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) based on intentionally asymmetrical polarized Al0.55Ga0.45N/Al0.4Ga0.6N/Al0.65Ga0.35N heterostructure has been fabricated and investigated, which achieves the self-powered capabilities. Operated at zero bias, the device presents an ultralow dark current of 7.8 x 10(-13) A, a high peak responsivity of 0.04 A/W at similar to 275 nm, a cut-off wavelength at similar to 285 nm, and a corresponding detectivity of 3.1 x 10(12) Jones. In comparison, the device with symmetrical heterostructure has no response at 0 V, confirming the effect of the proposed asymmetrical MSM structure. Furthermore, it is expressly demonstrated that the structure provides an asymmetrical energy band due to different barrier heights at the metal/Al0.4Ga0.6N and metal/Al0.55Ga0.45N/Al0.4Ga0.6N Schottky contacts and enhances the built-in electric field in the Al0.4Ga0.6N active layer owing to its polarization effect through simulations theoretically. Therefore, the improvement of photogenerated carrier transport can be obtained at 0 V, contributing to the high-performance self-powered UV PD.