Impact of silicon doping on low frequency charge noise and conductance drift in GaAs/AlGaAs nanostructures

We present measurements of low frequency charge noise and conductance drift in modulation doped GaAs/AlGaAs heterostructures grown by molecular beam epitaxy in which the silicon doping density has been varied from $2.4\times 10^{18} cm^{-3}$ (critically doped) to $6.0\times 10^{18} cm^{-3}$ (overdoped). Quantum point contacts were used to detect charge fluctuations. A clear reduction of both short time scale telegraphic noise and long time scale conductance drift with decreased doping density was observed. These measurements indicate that the {\it neutral} doping region plays a significant role in charge noise and conductance drift.