Contact

Configuration for a contact.

name#

name: str

A unique name for the contact.

origin#

origin: tuple[float, float, float] = (0.0, 0.0, 0.0)

The origin of the contact region in Å.

This is used to automatically determine the orbitals that belong to this contact.

lattice_vectors#

lattice_vectors: list[list[float]]

The lattice vectors of the contact cell in Å.

In "wf" simulations this is used to automatically determine the orbitals that belong to this contact.

The volume of the contact cell is also used to determine the Fermi level of the contact from its doping density and the density of states of its band structure.

direction#

direction: Literal['a', 'b', 'c'] | None = None

The direction from contact to the device.

This is used to find periodic images of the contact in transport direction.

fermi_level#

fermi_level: float | None = None

The Fermi level of the contact.

If not set, the Fermi level is automatically determined from the band structure of the contact via the mid_gap_energy parameter.

When set explicitly, this may lead to physically inconsistent results, especially in the context of Schrödinger-Poisson simulations.

mid_gap_energy#

mid_gap_energy: float | None = None

An energy lying somewhere in the band gap of the contact.

This is used to separate conduction from valence band states, which is necessary to automatically determine a contact's Fermi level, and to compute the excess carrier density that is used in computing the electrostatic potential in the Poisson solver.

This is also necessary when band-edge tracking is enabled in "negf" simulations, since the band edges, and their initial distance to the Fermi level, are determined via the mid-gap energy.

num_kpoints_transport#

num_kpoints_transport: int = 50

Number of k-points to use for contact band structure calculation.

This is used when automatically determining the Fermi level of the contact from its band structure. The k-point grid along the transverse directions are determined from the kpoint_grid parameter.

temperature#

temperature: NonNegativeFloat = 300.0

The temperature of the contact.

voltage#

voltage: float = 0.0

The voltage applied to the contact.

At least one contact needs to be grounded (i.e. have zero voltage) to serve as a reference for the other voltages.

The voltage and the Fermi level of the contact are used to determine its chemical potential.