 At higher temperatures, they behave like intrinsic semiconductors as the carriers from the donors/acceptors become insignificant compared to the thermally generated carriers.In non-crystalline semiconductors, conduction can occur by charges quantum tunnelling from one localised site to another.This is known as variable range hopping and has the characteristic form of

where "n" = 2, 3, 4, depending on the dimensionality of the system.