Abstract: Two-dimensional materials offer a vast range of band structures, yet experiments have explored only a narrow portion of them, in part because conventional electrostatic gating limits the accessible carrier density. We use two approaches to extreme doping of 2D materials while preserving high mobility: modulation doping by proximity to α-RuCl3 and electrostatic gating by using a high-k dielectric SrTiO3. In modulation-doped bilayer graphene we populate the second hole sub-band and analyze quantum oscillations, while monolayer graphene allows us to identify a magnetic transition in α-RuCl3. Finally, I will discuss our efforts to use thin films of the high-k dielectric to reversibly dope 2D materials.