Layer interdependence of transport in an undoped electron-hole bilayer
  The layer interdependence of transport in an undoped electron-hole bilayer (uEHBL) device was studied as a function of carrier density, interlayer electric field, and temperature. The uEHBL device consisted of a density tunable, independently contacted two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) induced via field effect in distinct GaAs quantum wells separated by a 30 nm Al$_{0.9}$Ga$_{0.1}$As barrier. Transport measurements were made simultaneously on each layer using the van der Pauw method. An increase in 2DHG mobility with increasing 2DEG density was observed, while the 2DEG mobility showed negligible dependence on the 2DHG density. Decreasing the interlayer electric-field and thereby increasing interlayer separation also increased the 2DHG mobility with negligible effects on the 2DEG mobility. The change in interlayer separation as interlayer electric-field changed was estimated using 2DHG Coulomb drag measurements. The results were consistent with mobility of each layer being only indirectly dependent on the adjacent layer density and dominated by background impurity scattering. Temperature dependencies were also determined for the resistivity of each layer. 
C. P. Morath, J. A. Seamons, J. L. Reno, and M. P. Lilly