Hall effect in the accumulation layers on the surface of organic semiconductors

We have observed the Hall effect in the field-induced accumulation layer on the surface of single-crystal samples of a small-molecule organic semiconductor rubrene. The Hall mobility mu(H) increases with decreasing temperature in both the intrinsic (high-temperature) and trap-dominated (low-temperature) conduction regimes. In the intrinsic regime, the density of mobile field-induced charge carriers extracted from the Hall measurements, n(H), coincides with the density n calculated using the gate-channel capacitance and becomes smaller than n in the trap-dominated regime. The Hall data are consistent with the diffusive bandlike motion of field-induced charge carriers between trapping events.