  We report the temperature dependent electrical transport properties of gated
bilayer graphene devices. We see a clear evidence of insulating behavior due to
electron-hole charge puddles. The electrical resistivity increases while the
mobility decreases with decreasing temperature, a characteristic due to carrier
inhomogeneity in graphene. The theoretical fittings using an empirical formula
of single electron tunneling indicate that electrical resistivity follows a
universal curve with a scaling parameter. The scaling parameter is determined
to be a measure of the fluctuations in the electron-hole puddle distribution.
