Anomalous Hall effect in microcrystalline Si:H films

The anomalous sign of the Hall coefficient in amorphous semiconductors is still poorly understood. It seems accepted, however, that an anomalous sign of the Hall coefficient indicates a different charge transport mechanism compared to free carrier motion on which the Lorentz force is acting. We find anomalous Hall coefficient signs in phosphorus-doped microcrystalline silicon films after irradiation with high energy electrons and subsequent annealing. These films are mixtures of amorphous and crystalline phases. We analyze measurements of Hall effect, electrical conductivity, and thermopower on such samples prior to and after electron irradiation and annealing, and use the anomalous Hall effect sign as a phenomenological indication of electronic transport in the amorphous phase. We deduce that the material consists of crystalline particles embedded in an amorphous matrix.