Conductivity, thermopower, and statistical shift in amorphous semiconductors

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Abstract
The temperature dependence of the thermopower and thermally activated conductivity is reflecting both the statistical shift of the Fermi level and the variation of the energy at which the transport mainly takes place. In amorphous semiconductors the two components are of comparable importance. It is shown that these contributions can be separated from each other by taking advantage of a simple relation between conductivity and thermopower, which has been disregarded so far. This discrimination allows us to extract new and more detailed information on the conduction mechanism, on the density of states, and on the position of the Fermi level from experimental data. In particular, the contribution to the transport at any energy may be obtained from a Laplace transformation of the temperature-dependent prefactor of the thermally activated conductivity. The analysis of data from samples with different amount of doping, which will be presented as an example, is of particular interest because of the information on doping-induced changes of mobility and density of states in the energy region where the transport takes place. DOI: http://dx.doi.org/10.1103/PhysRevB.19.2083 © 1979 The American Physical Society