Lighting the way to graphene-based devices
Berkeley Lab researchers use light to dope graphene boron nitride heterostructures
Graphene is a single layer of carbon atoms arranged in a hexagonal lattice. Boron nitride is a layered compound that features a similar hexagonal lattice – in fact hexagonal boron nitride is sometimes referred to as "white graphene." Bound together by the relatively weak intermolecular attraction known as the van der Waals force, GBN heterostructures have shown high potential to serve as platforms not only for high-electron-mobility transistors, but also for optoelectronic applications, including photodetectors and photovoltaic cells. The key to future success will be the ability to dope these materials in a commercially scalable manner. The photo-induced modulation doping technique developed by Wang and a large team of collaborators meets this requirement as it is comparable to the photolithography schemes widely used today for mass production in the semiconductor industry. Illumination of a GBN heterostructure even with just an incandescent lamp can modify electron-transport in the graphene layer by inducing a positive-charge distribution in the boron nitride layer that becomes fixed when the illumination is turned off.
"We've shown show that this photo-induced doping arises from microscopically coupled optical and electrical responses in the GBN heterostructures, including optical excitation of defect transitions in boron nitride, electrical transport in graphene, and charge transfer between boron nitride and graphene," Wang says. "This is analogous to the modulation doping first developed for high-quality semiconductors."
While the photo-induced modulation doping of GBN heterostructures only lasted a few days if the sample was kept in darkness – further exposure to light erased the effect – this is not a concern as Wang explains.
"A few days of modulation doping are sufficient for many avenues of scientific inquiry, and for some device applications, the rewritability we can provide is needed more than long term stability," he says. "For the moment, what we have is a simple technique for inhomogeneous doping in a high-mobility graphene material that opens the door to novel scientific studies and applications."
Original publication
Long Ju, Jairo Velasco Jr., Edwin Huang, Salman Kahn, Casey Nosiglia, Hsin-Zon Tsai, Wei Yang, Takashi Taniguchi, Kenji Watanabe, Yuanbo Zhang, Guangyu Zhang, Michael Crommie and Alex Zettl; "Photoinduced doping in heterostructures of graphene and boron nitride."; Nature Nanotechnology.
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Original publication
Long Ju, Jairo Velasco Jr., Edwin Huang, Salman Kahn, Casey Nosiglia, Hsin-Zon Tsai, Wei Yang, Takashi Taniguchi, Kenji Watanabe, Yuanbo Zhang, Guangyu Zhang, Michael Crommie and Alex Zettl; "Photoinduced doping in heterostructures of graphene and boron nitride."; Nature Nanotechnology.
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