Field-effect-induced two-dimensional electron gas utilizing modulation   doping for improved ohmic contacts
  Modulation-doped AlGaAs/GaAs heterostructures are utilized extensively in the study of quantum transport in nanostructures, but charge fluctuations associated with remote ionized dopants often produce deleterious effects. Electric field-induced carrier systems offer an attractive alternative if certain challenges can be overcome. We demonstrate a field-effect transistor in which the active channel is locally devoid of modulation-doping, but silicon dopant atoms are retained in the ohmic contact region to facilitate reliable low-resistance contacts. A high quality two-dimensional electron gas is induced by a field-effect and is tunable over a wide range of density. Device design, fabrication, and low temperature (T= 0.3K) transport data are reported. 
Sumit Mondal, Geoffrey C. Gardner, John D. Watson, Saeed Fallahi, Amir   Yacoby, and Michael J. Manfra
cond-mat.mes-hall