Epitaxial Topological Insulator Bi 2 Te 3 for Fast Visible to Mid-Infrared Heterojunction Photodetector by Graphene As Charge Collection Medium.

Three dimensional topological insulators have a thriving application prospect in broadband photodetectors due to the possessed topological quantum states. Herein, a large area and uniform topological insulator bismuth telluride (Bi 2 Te 3 ) layer with high crystalline quality is directly epitaxial grown on GaAs(111)B wafer using a molecular beam epitaxy process, ensuring efficient out-of-plane carriers transportation due to reduced interface defects influence. By tiling monolayer graphene (Gr) on the as-prepared Bi 2 Te 3 layer, a Gr/Bi 2 Te 3 /GaAs heterojunction array prototype was further fabricated, and our photodetector array exhibited the capability of sensing ultrabroad photodetection wavebands from visible (405 nm) to mid-infrared (4.5 μm) with a high specific detectivity ( D* ) up to 10 12 Jones and a fast response speed at about microseconds at room temperature. The enhanced device performance can be attributed to enhanced light-matter interaction at the high-quality heterointerface of Bi 2 Te 3 /GaAs and improved carrier collection efficiency through graphene as a charge collection medium, indicating an application prospect of topological insulator Bi 2 Te 3 for fast-speed broadband photodetection up to a mid-infrared waveband. This work demonstrated the potential of integrated topological quantum materials with a conventional functional substrate to fabricate the next generation of broadband photodetection devices for uncooled focal plane array or infrared communication systems in future.