Metal Contact
The Metal Contact node is used for modeling metal–semiconductor contacts.
The Harmonic Perturbation subnode (it is of the exclusive type) is available from the context menu (right-click the parent node) or in the Physics toolbar, click the Attributes menu and select Harmonic Perturbation.
Terminal
Specify the terminal properties. To indicate which boundaries belong to the same terminal, enter the same name in the Terminal name field. The Terminal name should be numeric for sweeps to work properly.
Select a Terminal type — Voltage (the default), Current, or Circuit. Select:
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 Voltage to enter an electric potential V0 (SI unit: V). The default is 0 V.
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 Current to enter a current I0 (SI unit: A). The default is zero current, corresponding to an open circuit.
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 Circuit (current) to specify a terminal connected to an external circuit, where the external circuit acts as a current source for the semiconductor model.
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 Circuit (voltage) to specify a terminal connected to an external circuit, where the external circuit acts as a voltage source for the semiconductor model.
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 Power to enter a current P0 (SI unit: W). The default is zero power, corresponding to an open circuit.
Contact resistance
Select the Contact resistance check box (default is disabled) to add an infinitesimally thin resistive layer, and then enter the Specific contact resistivity ρc (SI unit: Ω·m2). The default is 1e-8[ohm*cm^2].
Contact Type
Select a Type — Ideal ohmic (the default) or Ideal Schottky.
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Use the Ideal ohmic option for a nonrectifying metal–semiconductor junction, that is a contact with negligible resistance relative to the total resistance of the modeled semiconductor device.
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Use the Ideal Schottky option for a simple rectifying metal–semiconductor junction, that is, when the current–voltage characteristics at the interface depend on the potential barrier formed at the junction. For this option, surface recombination effects and surface charge densities associated with surface traps can be included in the model by adding Trap-Assisted Surface Recombination boundary conditions to the same boundary selection as the Metal Contact boundary condition.
Contact properties
This section is available if Ideal Schottky is selected as the contact Type.
Choose between an Ideal (the default) and User defined definition of the Barrier height.
For the Ideal barrier height, the default Metal work function Φ (SI unit: V) is 4.5 V. The metal work function is the difference in energy between the vacuum level and the conduction band at equilibrium in the metal in contact with the semiconductor. The ideal barrier height is given by the difference between the metal work function and the electron affinity of the semiconductor.
For the User defined barrier height, enter a value for the Barrier height ΦB (SI unit: V). In this case, the metal work function is not used.
Thermionic Currents
This section is available if Ideal Schottky is selected as the contact Type.
Select the Thermionic currents — Richardson’s coefficients (the default) or Surface recombination velocities.
For Richardson’s coefficients enter an:
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 Effective Richardson constant for electrons An* (SI unit: A/(m2⋅K2)). The default constant is 110 A/(K⋅cm)2 for silicon.
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 Effective Richardson constant for holes Ap* (SI unit: A/(m2⋅K2)). The default constant is 90 A/(K⋅cm)2 for silicon.
For Surface recombination velocities enter a:
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 Surface recombination velocity, electrons Vs,n (SI unit: m/s). The default is 21,605 m/s for silicon.
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 Surface recombination velocity, holes Vs,p (SI unit: m/s). The default is 19,006 m/s for silicon.
Extra Current Contribution
This section is available if Ideal Schottky is selected as the contact Type.
The settings are the same as described in this section Extra Current Contribution.
Constraint Settings
This section is available when a finite element formulation is used. To display this section, click the Show More Options button () and select Advanced Physics Options. For Current, Circuit (current), and Power terminals, weak constraints are used by default.
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Boundary Conditions and Metal Contacts
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Small-Signal Analysis
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Harmonic Perturbation, Prestressed Analysis, and Small-Signal Analysis in the COMSOL Multiphysics Reference Manual.