Carrier transport mechanism in graphene on SiC(0001)

Carrier density and temperature-dependent transport properties of monolayer graphene grown on SiC(0001) were systematically studied. With increasing temperature, resistivity at the charge neutrality point decreases, while resistivity away from the charge neutrality point, where the carrier density is above 1 x 10(11) cm(-2), increases. From Hall measurements and the temperature dependence of conductivity, carrier density at the charge neutrality point at 2 K is estimated to be 1 x 10(10) cm(-2) or below. Such low carrier density implies a small potential fluctuation in graphene on SiC(0001). The carrier density at the charge neutrality point increases with increasing temperature and thus the resistivity decreases. At carrier densities away from the charge neutrality point, the mobility decreases with increasing temperature and the resistivity increases. We analyzed the decrease of mobility, assuming phonon scatterings that originate from the substrate.