FDCharge Control Panel #

This section introduces the FDCharge simulation control panel.

Finite Difference Charge Transport (FDCharge) solver resolves Poisson and carrier transport equations for active photonic devices and is suitable for simulating carrier transport in semiconductor devices.

The control panel contains buttons and displays for basic active-device settings and simulation information, as shown below:

Name	Description
Design	To Design: return to simulation design.
Progress	Shows simulation progress.
Status	Shows simulation status.
Run	Run active (DC) simulation.
Tool	Controls opening and clearing of data files.

FDCharge Feature #

The FDCharge solver includes features different from passive solvers, such as independent doping settings and active-parameter monitors. The feature buttons are shown below:

Name	Description
Constant Doping	Add uniform doping; defines a region with uniform dopant concentration.
Diffusion Doping	Add diffusion doping; define a region with dopant distribution function.
Import Generation	Import generation rates produced by passive simulations (commonly used for photodetector designs).
Device Monitor	Add device (active) parameter monitors to record optical/electrical fields in a region.
Analysis Group	Add analysis groups.
Mesh	Add custom mesh.
To Run	Run simulation.

Doping #

These FDCharge settings define doped semiconductors. Note: Doping applies only to semiconductor materials; doping in non-semiconductor regions is automatically ignored during computation, so you do not need to worry if a doping region overlaps non-semiconductor regions.

Two doping methods are supported: uniform (constant) doping and functional (diffusion) doping. Doping contributions are cumulative: if multiple doping objects apply to a region, the net doping is the sum of their concentrations. N-type and P-type dopants have opposite signs and will partially cancel each other.

Constant Doping #

Defines a semiconductor region with a fixed dopant concentration. Users specify the geometry and parameters of the region.

Parameters:

Name	Description
General	Set the doping object's name.
X / Y / Z	Set the center position and extent of the doping region.
Dopant	Doping settings. Dopant Type: choose p for hole (acceptor) or n for electron (donor). Concentration: dopant concentration in atoms per cubic centimeter ($cm^{-3}$).

Diffusion Doping #

Functional doping defines concentration by a distribution function. Two distribution types are supported: 1) constant surface-source diffusion (erfc function) and 2) finite surface-source diffusion (gaussian function).

Parameters:

Name	Description
Dopant Type	Choose dopant type: p for holes (acceptors), n for electrons (donors).
Source Face	The face where doping is injected.
Junction Width	Width over which concentration drops from maximum to minimum according to the distribution.
Distribution Function	Select the doping distribution function.
Concentration	Maximum dopant concentration (atoms per $cm^{-3}$).
Ref Concentration	Minimum dopant concentration (atoms per $cm^{-3}$).

Generation #

Import Generation #

This option imports photogeneration (generation rate) results produced by a passive simulation. It is commonly used in photodetector simulation designs.

Monitor #

The FDCharge solver provides Device monitors (active parameter monitors). Monitors are typically set to match the FDCharge simulation region.

Device Monitor #

Device monitors can record optical, electrical, and other related quantities. The available parameters are:

Name	Physical Quantity	Units	Description
Electrostatics	E	V/m	Electric field.
	V	V	Electric Potential
	Ei	eV	Intrinsic energy.
	Ec	eV	Conduction band.
Bandstructure	Ev	eV	Valence band.
	Efn	eV	Electron quasi-Fermi level.
	Efp	eV	Hole quasi-Fermi level.
	ND	$cm^{-3}$	Donor concentration.
Doping	NA	$cm^{-3}$	Acceptor concentration.
	N	$cm^{-3}$	Net doping density (N = NA - ND).
	n	$cm^{-3}$	Electron concentration.
	p	$cm^{-3}$	Hole concentration.
Charge	np	$cm^{-3}$	Charge product (np = sqrt(n * p)).
	jn	$A/(cm^{2})$	Electron current density.
	jp	$A/(cm^{2})$	Hole current density.
	J	$A/(cm^{2})$	Total current density (jn - jp).
Recombination	G	$s/cm^{-3}$	Imported generation rate.
	dn		Change in n.
Delta Index	dk		Change in k.
	Depsr		Change in permittivity.