Electron transport of inhomogeneous Schottky barriers: A numerical study

Abstract

Numerical simulations are presented of the potential distribution and current transport associated with metal-semiconductor (MS) contacts in which the Schottky barrier height (SBH) varies spatially. It is shown that the current across the MS contact may be greatly influenced by the existence of SBH inhomogeneity. Numerical simulations indicate that regions of low SBH are often pinched-off when the size of these regions is less than the average depletion width. Saddle points in the potential contours in close proximity to the low-SBH regions, which are shown to vary with the dimension and magnitude of the inhomogeneity as well as with bias, essentially determine the electron transport across the low-SBH regions. It is these dependences of the saddle point which give rise to various abnormal behaviors frequently observed from SBH experiments, such as ideality factors greater than unity, various temperature dependences of the ideality factor, including the T0 anomaly, and reverse characteristics which are strongly bias-dependent. The results of these numerical simulations are shown to support the predictions of a recently developed analytic theory of SBH inhomogeneity.

Temperature dependence of current density and admittance in metal-insulator-semiconductor junctions with molecular insulator

“…(5)). Again, this discrepancy supports the assumption made in the interpretation of experimental n(V) results, namely the existence of a distribution of barrier heights [38][39][40] due to surface potential fluctuations arising from some inhomogeneous distribution of dipoles or charged defects.…”

“…This interpretation of high n values is supported by the discrepancy between the barrier heights obtained from C(V) and I(V) characteristics, as shown by modelling studies. [38][39][40] V. CONCLUSION Electrical transport mechanisms in rectifying Hg// C 12 H 25 -n Si(111) junctions with nanometer thick molecular insulator have been investigated using the temperature dependence of current density J(V, T) and admittance Y(V, T, x) characteristics. With low doped n-type silicon, J(V) characteristics show a strong rectification (R !…”

“…6(a)) is consistent with a larger relative contribution of low barrier patches in the junction. [38][39][40] The effective barrier height qU EFF ðVÞ was derived in the TE approximation using n(V) and Eqs. (5) and (6).…”

Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects

“…Such excess current resulting from non-uniform Schottky contacts has extensively been reported in electronic device literature. [52][53][54][55][56][57][58][59][60][61][62][63][64] A realistic model for calculating (I-V) characteristics considers a distribution of low barrier height patches ðqU HOM B À D P Þ embedded in an extended region of homogeneous but larger barrier heights ðqU HOM B Þ. When the Schottky barrier height varies with large amplitudes on small lateral length scale, the conduction path in front of a patch with low barrier height is partially blocked by the presence of high barrier height patches in its close proximity.…”

“…54,55,59,60 In the dipole approximation, valid for a circular patch radius R P smaller than the width of the space charge layer, W, the local barrier height…”