3D Dirac semi-metal Cd3As2/Bi2O2Se film heterojunction for visible to near infrared photo-detection

Abstract

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 (R_i) 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 (R_i) 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.