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Cd3As2 is a representative three-dimensional (3D) Dirac semi-metal material, which is expected to develop high-performance wide spectrum photodetectors due to the unique optical and electrical properties. For instance, the band structure exhibits a unique three-dimensional Dirac structure which express the characteristics of zero band-gap and full spectral absorption, high photocurrent response and the ultra-high charge mobility, these characteristics make it a more potential candidate for photodetection. However, arising from its excellent conductivity, the extremely high dark currents in 3D semi-metal-based photodetector is an imperfection that limit the development of individual Cd3As2 film photoconductive detector. Here in, we developed an Cd3As2/Bi2O2Se heterojunction by thermal depositing Bi2O2Se film on the as-prepared Cd3As2 film. The Cd3As2/Bi2O2Se heterojunction film photodetector demonstrates a relative broad spectrum photodetection from visible (405nm) to near infrared (1310nm) at room temperature with high responsivity (Ri) and fast response time (τ). These results show that the dark current is reduced about a half compared to the individual Cd3As2 film at the same bias voltage. Subsequently, at the bias voltage of three volts, we tested the detector performance under 808nm laser irradiation, in which the maximum photocurrent responsivity (Ri) can be reached to 17.8 mA/W. We analyze that the greatly enhanced-performance improvement of the device maybe originated from its vertical structure advantages, due to the formed internal potential barrier would be accelerates the speed of collecting carrier. This work provides a suitable method and reference for fabricating broad-spectrum and high-speed Cd3As2 based inorganic photodetectors.
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