Structured Back Gates for High-Mobility Two-Dimensional Electron Systems   Using Oxygen Ion Implantation
  We present a new approach of back gate patterning that is compatible with the requirements of highest mobility molecular beam epitaxy. Contrary to common back gating techniques, our method is simple, reliable and can be scaled up for entire wafers. The back gate structures are defined by local oxygen implantation into a silicon doped GaAs epilayer, which suppresses the conductance without affecting the surface quality. 
Matthias Berl, Lars Tiemann, Werner Dietsche, Helmut Karl, and Werner   Wegscheider
cond-mat.mes-hall