A model of the intimate metal-semiconductor Schottky-barrier contact

Abstract

On the basis of numerical analysis, a model of the intimate metal-semiconductor Schottky-barrier (SB) contact is proposed. According to this model, the Fermi-level pinning at the contact is due to high density of electron surface states in equilibrium with the metal, whereas the IV characteristic distortions (deviation from ideality) are due to a continuous (and/or discrete) spectrum of the energy-and coordinate distributed (in the general case) nearsurface states in equilibrium with the semiconductor. This model amplifies the Bardeen model for actual SB contacts that is limited by the assumption of the presence of an intermediate insulating layer. However, the assumption is not necessarily fulfilled for the contacts manufactured using currently available technologies.

Influence of the nonlinear bias dependence of the barrier height on measured Schottky-barrier contact parameters

“…1 Because of this the Fermi-level position in n-GaAs was determined by a numerical solution of the charge neutrality equation. 28 The Fermi-Dirac carrier distribution was also used at calculating current through the contact according to Eq. (1).…”

“…7, is connected with similarity of the IVCs [in the form (12)] for all contacts, which behavior is significantly affected by the nonlinear bias dependence of actual or effective barrier height. Among these are tunnel contacts, 31 contacts with intermediate layer and interface states, 27 intimate contacts with subsurface states, 28 inhomogeneous contacts 29 and possibly others.…”

“…[27][28][29], one can state that the model of SBC considering the nonlinear bias dependence of the barrier height, can be the basis for the adequate description and explanation of "anomalous" properties of both ideal (in the sense explained above) and real contacts. It seems to be evident that the specific mechanisms that cause the nonlinear dependence of barrier height can be quite different in different contacts.…”

“…These are, for example, inhomogeneous (by energy) distribution of interface states communicating with semiconductor in the contact with an intermediate insulating layer and IS, 19,20,27 subsurface (near the interface) states distributed over the coordinate and energy in the intimate contact, 28 barrier height inhomogeneities, 17,29 image force in the ideal contact, the influence of which is an immediate cause of the barrier height nonlinearity, 30 and even the tunnel effect, 31 the low temperature behavior of which seems to have natural physical explanation. Other possible reasons of barrier height nonlinearity are mentioned, for example, in the work.…”

On the current-voltage characteristic of a tunnel metal-semiconductor Schottky-Barrier contact

“…(5) similar to the (I-V) characteristic of any non-tunnel contact: e.g., an ideal contact [9], a real contact with an intermediate layer, or an intimate contact [13]. The difference is that in the case of the tunnel contact, the barrier height included in Eq.…”