  We studied the magneto-transport properties of graphene prepared by
exfoliation on a III V semiconductor substrate. Tuneability of the carrier
density of graphene was achieved by using a doped GaAs substrate as a
back-gate. A GaAs/AlAs multilayer, designed to render the exfoliated graphene
flakes visible, also provides the required back-gate insulation. Good
tuneability of the graphene carrier density is obtained, and the typical Dirac
resistance characteristic is observed despite the limited height of the
multilayer barrier compared to the usual SiO2 oxide barrier on doped silicon.
In a magnetic field weak localization effects as well as the quantum Hall
effect of a graphene monolayer are studied.
