Undoped Electron-Hole Bilayers in a GaAs/AlGaAs Double Quantum Well

We present the fabrication details of completely undoped electron-hole bilayer devices in a GaAs/AlGaAs double quantum well heterostructure with a 30 nm barrier. These devices have independently tunable densities of the two-dimensional electron gas and two-dimensional hole gas. We report four-terminal transport measurements of the independently contacted electron and hole layers with balanced densities from $1.2\times {10}^{11}$cm${}^{-2}$ down to $4\times {10}^{10}$ cm${}^{-2}$ at $T=300mK$. The mobilities can exceed $1 \times 10^{6}$cm$^{2}$V$^{-1}$s$^{-1}$forelectronsand$4 \times 10^{5}$cm$^{2}$V$^{-1}$s$^{-1}$ for holes.