Charge carrier transport tunnelling through barrier

Superlattice structures yield efficient charge transport normal to the layers, because the charge carriers can move through the minibands the narrower the barrier, the wider the miniband and the higher the carrier mobility. Transport in MQWs with thick barriers requires thermionic emission of carriers over the barriers, or if electric fields are applied, field-assisted tunnelling through the barriers (Parsons et al, 1990). 

The room temperature conductivities of polycrystalline samples of [(PcMO)lv] (M = Si, Ge) for various stoichiometries are given in Table 15.1. The nature of the dopant (iodine, bromine, quinones, etc.) has no significant effect on the conductivities [125,128-130], In addition to the main charge transport mechanism via the phthalocyanine system, other mechanisms, e.g, percolation theory and fluctuation-induced carrier tunneling through potential barriers separating metal-like regions, have also been discussed [131]. 

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