  We investigate carrier transport in a single 22 nm-thick double-gated Si
quantum well device, which has independent contacts to electrons and holes.
Conductance, Hall density and Hall mobility are mapped in a broad double-gate
voltage window. When the gate voltage asymmetry is not too large only either
electrons or holes occupy the Si well and the Hall mobility shows the
fingerprints of volume inversion/accumulation. At strongly asymmetric
double-gate voltage an electric field induced electron-hole (EH) bi-layer is
formed inside the well. The EH drag resistance R_{he} is explored at balanced
carrier densities: R_{he} decreases monotonically from 860 to 37 Ohms when the
electron and hole density is varied between ~0.4-1.7x10^{16} m^{-2}.
