Graphene helps flatten gallium nitride

Materials researchers have laid down gallium nitride as a two-dimensional material for the first time with some help from graphene sheets. Getting GaN to flatten out took some doing because the semiconductor’s 3-D crystals don’t exist naturally as stacks of atomic layers, as is the case with graphene, hexagonal boron nitride, and most other 2-D materials. A team led by Joan M. Redwing and Joshua A. Robinson of Pennsylvania State University confined gallium and nitrogen atoms in a narrow gap between a defect-rich graphene bilayer and a silicon carbide substrate to realize 2-D GaN (Nat. Mater. 2016, DOI: 10.1038/nmat4742). Using a chemical vapor deposition system, the researchers first decomposed trimethylgallium gas to work gallium atoms into the bilayer’s defects, allowing gallium to accumulate between the graphene and silicon carbide. They then liberated nitrogen from ammonia gas, with the nitrogen migrating through the graphene to react with gallium and create discrete islands of 2-D GaN. With an electronic band gap larger than bulk GaN, 2-D GaN could provide an attractive material for electronic and optoelectronic applications, the team says. In the more immediate future, the researchers are working to create larger, continuous GaN films and to create other new 2-D materials using the graphene-capped synthesis.