Publications Details
Artificial Graphene in Undoped Semiconductor Heterostructures
Lu, Tzu-Ming L.; Tracy, Lisa A.
The linear energy-momentum dispersion which arises from graphene’s underlying honeycomb lattice gives graphene its unique electronic properties unfound in conventional semiconductors. Theoretically speaking, when an electrostatic potential with hexagonal or honeycomb symmetry is imposed onto a two-dimensional electron/hole system, the band structure is modified in a way that the same linear energy-momentum dispersion could exist. Experimentally, there has not been any evidence from transport demonstrating the so-called “artificial graphene”. In this project, we attempt to create an artificial superlattice potential with hexagonal symmetry for two dimensional carriers in an undoped SiGe heterostructure by patterning a nanoscale hole array in a metallic gate. Using undoped heterostructures allows us to access a very wide density range, which covers the magic densities at which the Dirac points are expected. A process flow for fabricating such field-effect-transistor devices with a lattice constant as small as 90 nm is reported. Magneto-transport measurements performed at 0.3 K show that the superlattice potential in the quantum well in which the two-dimensional system resides is indeed modulated by the gates. However, no signature of the sought-after linear dispersion is observed in the transport data.