Double two-dimensional electron gas structure formed by molecular beam epitaxy regrowth on an ex situ patterned n +-GaAs back gate

We have regrown two two-dimensional electron gases (2DEGs) in a wide GaAs quantum well on a large area ex situ patterned n+-GaAs back gate. The transport in these channels is controlled by this gate and a surface front gate. We present results showing the control that the patterned back gate has over the carrier concentration in the low mobility back 2 DEG and the very low leakage currents that are observed from the back gate to the source-drain channel at 1.5 K. Using four terminal resistance and magnetoresistance data the transition from two conducting channels to conduction in the low mobility back 2DEG is shown. The implications of these results for the fabrication of velocity modulated transistors are discussed.