Transport Processes in Polycrystalline Films

3 Transport Processes in Polycrystalline Films 2.2.3.1 Dislocation Scattering 

This process is obviously a natural scattering process in polycrystalline materials, since polycrystalline films exhibit a high concentration of crystallographic defects, especially dislocations [133,134]. However, this process is rarely used to explain experimental data of carrier transport in polycrystalline semiconductors and especially transparent conducting oxides [88], which is mainly due to the fact that in most works on transport properties of polycrystalline films the density of defects was not determined. Podor [135] investigated bended n-type Ge crystals with a dislocation density around 107 cm 2 

Both models yield an effective mobility p,eg dominated by thermionic emission across the grain barriers with an energetic height b  

Depending on the doping concentration in the grains, two expressions for the barrier height can be derived  

For polycrystalline films this limited understanding is nicely illustrated by our own mobility data for Al-doped ZnO films (see Fig. 2.15) deposited both on glass and sapphire substrates as a function of the carrier concentration 

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