We fabricated gated-Hall bar devices from two types of graphene heterostructures: a graphene-on-hBN (GB) and b graphene encapsulated in hBN (BGB). The dashed green box in the optical images shows the device active region. The scale bars are 10 μm. The narrow FWHM of the four-point longitudinal resistivity (ρxx) of the c GB and d BGB devices suggests a low-charge inhomogeneity (n*) in graphene. The insets in c and d show the estimated n* of the GB and BGB devices. e The carrier-density-dependent mobility of the BGB-1 device at room temperature, giving mobility in excess of 200,000 cm2 V−1 s−1 at low carrier densities. For comparison, we provided the theoretically predicted acoustic phonon-limited mobility45. f The corresponding low-temperature mobility of the BGB-1 device is 800,000 cm2 V−1 s−1 at low carrier densities.