Hydrogenation technique triples transistor performance in epitaxial graphene

The Penn State University team, led by materials scientist Joshua Robinson, achieved the 3x improvement in electron mobility by turning the buffer layer of a transistor into a second, free floating one atom thick layer of graphene. They did this by passivating dangling carbon bonds using hydrogen, which resulted in two free floating layers of graphene. According to Robinson, the researchers were able to achieve an extrinsic cut off frequency of 24GHz in transistor performance, the highest reported so far in a real world epitaxial graphene device. "There are two faces to a silicon carbide wafer," explained Robinson. "Graphene grown on the carbon face usually has higher electron mobility, but that's because beneath the graphene layer grown on the silicon face there is a carbon rich buffer layer bound to the silicon carbide that acts to scatter electrons, thus reducing their mobility. "If you can get rid of the buffer layer, the electrons will go much faster, which means your devices will work faster. It is also easier to control the thickness of the graphene on the silicon face, which is crucial if you want to make highly uniform wafer scale devices. That's what we've been able to do." The Penn State team is now looking to use the hydrogenation technique to improve transistor performance in radio frequency devices.