Charge transport in polycrystalline silicon thin films on glass substrates

Charge carrier transport in solid phase crystallized polycrystalline silicon poly Si was investigated as a function of the deposition temperature, Td, the amorphous starting material and the used substrates. The samples were characterized using temperature dependent transport measurements to determine the carrier concentration, mobility, and conductivity. Samples prepared on a SiN H covered Borofloat glass exhibit a low carrier concentration that is independent of Td. In these samples charge transport is dominated by intra grain scattering mechanisms. In contrast, when poly Si is prepared on Corning glass the carrier concentration shows an inverted U shape behavior with increasing deposition temperature. The Hall mobility is thermally activated, which is consistent with thermionic carrier emission over potential energy barriers. The change of the activation energy with experimental parameters is accompanied by a large change of the exponential prefactor by more than 4 orders of magnitude. This is indicative of a Meyer Neldel behavior. Moreover, at low temperatures the conductivity deviates from an activated behavior indicating hopping transport. To derive insight into the underlying transport mechanisms and to determine information on barrier energy heights and grain boundary defect densities the experimental data were analyzed employing transport models for polycrystalline material