Dec 19, 2016
Photo doping pushes graphene UV photodetector to the limit
The ultraviolet (UV) photodetector is one of the most important optoelectronic devices that are widely used in the commercial field. Reporting in Nanotechnology, we demonstrate a graphene/h-BN/GaN heterostructure ultraviolet photodetector fabricated through a photo-induced doping technique. The photodetector has an extremely high responsivity of 1915 A/W, which is the highest reported for a graphene-based UV photodetector. The detectivity of the device is more than 1.02 × 1013 Jones (Jones=cm Hz1/2W-1 ).
Inorganic photodetectors, which are typically made from silicon or gallium nitride based p-n junction photodiodes, are unsuitable for certain applications because of their high cost and low responsivity (<0.2A/W). Forming graphene-based heterostructures with bulk semiconductors is very promising for competitive commercial photodetectors.
The key for pushing a graphene UV photodetector to the limit is dynamically doping graphene by UV light itself. In the first step, we inset the h-BN layer into the graphene/GaN heterostructure for suppressing the static charge transfer from GaN to graphene. The interfaced h-BN layer increases the barrier height at the graphene/GaN heterojunction and enhances the performance of our device.
Furthermore, coating the graphene/BN/GaN heterostructure with ZnO quantum dots brings the photo-induced doping technique to this UV photodetector. ZnO quantum dots can absorb the UV light efficiently as they have a band gap larger than 3.1 eV and a large exciton binding energy larger than 60 meV as a result of the quantum confinement effect. The absorbed photons in ZnO quantum dots produce a large amount of electron-hole pairs. The photo-induced holes in ZnO can effectively inject into the graphene layer and move the Fermi level of graphene down, which enlarges the barrier height between graphene and GaN and improves the performance of graphene/GaN photodetector.
By optimizing the photo-induced doping technique, we have a chance of pushing the graphene UV photodetector to the limit. The photo-doped graphene/GaN heterostructure has a great future for commercial UV photodetector applications.
Full details are reported in Nanotechnology.
About the author
Prof. Shisheng Lin led the work with a pioneering group in the department of information science and electronic engineering at Zhejiang University. We implement novel physics carried by novel materials into the traditional devices and create high-performance optoelectronic and electronic devices. We have achieved high performance two-dimensional materials based solar cells, photodetectors and light-emitting diodes. Prof. Lin has demonstrated the possibility of fabrication of two-dimensional SiC, SiC2 and silicon doped graphene, which provides a solution for band gap engineering of graphene. Prof. Lin has published more than 60 international peer-reviewed journal papers with over 1000 citations.
• Ultrafast quantum-dot photodetector detects multiple electrons (Sep 2015) • 3D periodic nanostructures enhance photodetector performance (Sep 2016) • Understanding the photosensitivity of resonant tunneling diode photodetectors (Aug 2016) • Light discussion on nanophotonics (Jan 2016)