Influence of charged-dislocation density variations on carrier mobility in heteroepitaxial semiconductors: The case of SnO₂ on sapphire

In highly mismatched heteroepitaxial systems, the influence of carrier- and dislocation-density variations on carrier mobility is revealed. Transmission electron microscopy reveals the variation of dislocation density through a series of SnO₂ films grown by molecular-beam epitaxy on sapphire substrates where the lattice mismatch exceeds 11%. A layer-by-layer parallel conduction treatment of the carrier mobility in SnO₂ epilayers is used to illustrate the dominant role of the depth-dependent dislocation density and charge profile in determining the film-thickness dependence of the transport properties.