Thin Insulator Gate
Use the Thin Insulator Gate node to model a thin insulating material between the semiconductor and a metal. The layer has the thickness dins and the relative permittivity εins. The indices ins and s refer r to the insulator and semiconductor side of the boundary, respectively.
The Harmonic Perturbation subnode (it is of the exclusive type) is available from the context menu (right-click the parent node) or on the Physics toolbar, click the Attributes menu and select Harmonic Perturbation.
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Small-Signal Analysis
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Harmonic Perturbation — Exclusive and Contributing Nodes in the COMSOL Multiphysics Reference Manual.
Continuation Settings
These settings are the same as for Fletcher Mobility Model (C).
Solving
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), Charge, 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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Charge to specify a charge Q0 (SI unit: C). This is the charge on the contact side of the parallel plate capacitor. The default is 0 V.
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Circuit to specify a terminal connected to an external circuit.
It is important to realize that the Charge setting does not specify an interface charge at the boundary between the semiconductor and the insulator—it specifies the charge on the top conductor of the gate capacitor.
Gate contact
Specify the insulator dimensions and permittivity as well as the metal work function.
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Oxide relative permittivity εins (dimensionless). The default relative permittivity is 1.
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Oxide thickness dins (SI unit: m). The default thickness is 0.1 μm.
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Metal work function Φ (SI unit: V). The default barrier height is 4.1 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 functionality of the Surface traps check box in versions prior to 5.4 has been replaced and expanded by the Trap-Assisted Surface Recombination boundary condition.
 
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Boundary Conditions and Thin Insulating Gates
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Harmonic Perturbation, Prestressed Analysis, and Small-Signal Analysis in the COMSOL Multiphysics Reference Manual.