The impact of barrier height distributions in tunnel junctions

We demonstrate that including continuous and discrete tunnel barrier height distributions in otherwise traditional tunneling formalisms enables straightforward modeling of several phenomena important to tunneling. Random barrier height inhomogeneities significantly impact the tunneling conductance, as evidenced by ideal tunneling models extracting faulty barrier parameters, with the incurred errors strongly dependent on the variance. Thermal smearing is addressed by transferring the energy distribution from the electrons to the barrier potential energy, thereby enabling zero-temperature tunneling models to model temperature dependent tunneling. For discrete tunneling channels, a secondary, impuritylike channel is shown to dominate the net conductance at surprisingly low impurity levels, implying that the observation of intrinsically large barrier heights is highly unlikely with transport measurements. Finally, spin-filter tunneling is modeled with independent tunneling channels whose barrier heights are linked to a temperature-dependent exchange splitting. © 2009 American Institute of Physics. DOI: 10.1063/1.3122600