DOUBLE 2-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 G aAs 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 surfa ce front gate. We present results showing the control that the pattern ed back gate has over the carrier concentration in the low mobility ba ck 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 re sistance and magnetoresistance data the transition from two conducting channels to conduction in the low mobility back 2DEG is shown. The im plications of these results for the fabrication of velocity modulated transistors are discussed. (C) 1994 American Institute of Physics.