Very high mobility has been found in several ultrapure low-dimensional systems, such as two-dimensional electron gases (2DEG) (35,000,000 cm /(V⋅s) at low temperature), carbon nanotubes (100,000 cm /(V⋅s) at room temperature) and freestanding graphene (200,000 cm /(V⋅s) at low temperature). Organic semiconductors (polymer, oligomer) developed thus far have carrier mobilities below 50 cm /(V⋅s), and typically below 1, with well performing materials measured below 10.