Transport and drag in undoped electron-hole bilayers

We investigate transport and Coulomb drag properties of semiconductor-based electron-hole bilayer systems. Our calculations are motivated by recent experiments in undoped electron-hole bilayer structures based on GaAs-AlGaAs gated double quantum well systems. Our results indicate that the background charged impurity scattering is the most dominant resistive scattering mechanism in the high-mobility bilayers. We also find that the drag transresistivity is significantly enhanced when the electron-hole layer separation is small due to the exchange induced renormalization of the single layer compressibility. However, the Fermi-liquid many-body approach cannot explain the recently observed upturn in the drag resistance with the lowering of temperature, which may be indicating the emergence of an apparent non-Fermi-liquid excitonic phase in closely spaced bilayers.