Fabrication of closely spaced, independently contacted electron-hole bilayers in GaAs-AlGaAs heterostructures

We describe a technique to fabricate closely spaced electron-hole bilayers in GaAs-AlGaAs heterostructures. Our technique incorporates a method for making shallow contacts to a low density (<1011cm−2) two-dimensional electron gas (2DEG) that do not require annealing. Four terminal measurements on both layers (25nm apart) are possible. Measurements show a hole mobility μh>105cm2V−1s−1 and an electron mobility μe>106cm2V−1s−1 at 1.5K. Preliminary drag measurements made down to T=300mK indicate an enhancement of coulomb interaction over the values obtained from a static random phase approximation (RPA) calculation.