# generation{}¶

Specifications that define information on generation rate.

## Syntaxes¶

### Specifications of generation rate profile¶

The generation rate profile is assiged to a certain region. The following syntaxes are put under structure{ region{ generation{} } }.

• constant

• linear

• gaussian1D

• gaussian2D

• gaussian3D

• import (import generation rate profile from external file)

constant

constant generation rate over the region

Example

constant{
rate = 1.0e18               # generation rate [1/cm³s] (applies to 1D, 2D and 3D)
add  = yes                  # (optional) yes or no (default = yes)
}

linear

linearly varying generation rate along the line from start to end point

Example

linear{
rate = [1e18,2e18]          # start and end value of generation rate [1/cm3s]
x    = [50.0,100.0]         # x coordinates of start and end point [nm]
y    = [50.0,100.0]         # y coordinates of start and end point [nm] (2D or 3D only)
z    = [50.0,100.0]         # z coordinates of start and end point [nm] (3D only)
# This defines a generation rate profile, which varies linearly along the line from the point (50,50,50) to the point (100,100,100)
# and stays constant in the perpendicular planes.
add  = yes                  # (optional) yes or no (default = yes)
}

gaussian1D

Gaussian distribution function in one direction, constant in perpendicular directions

Example

gaussian1D{                     # Gaussian distribution function in one direction, constant in perpendicular directions
rate    = 1.0e18            # maximum of generation rate [1/cm3s]
dose    = 1e12              # dose of implant [cm-2] (integrated density of gaussian function), typical ranges are from 1e11 to 1e16.
# Either rate or dose has to be specified, but not both simultaneously.
# rate = dose / ( SQRT(2*pi) * sigma_x )
x       = 50.0              # x coordinate of Gauss center (ion's projected range Rp, i.e. the depth where most ions stop) [nm]
sigma_x = 5.0               # root mean square deviation in x direction (statistical fluctuation of Rp) [nm]
y       = ...               # (2D or 3D only)
sigma_y = ...               #
z       = ...               # (3D only)
sigma_z = ...               #
# Only one out of x, y, z and the appropriate standard deviation (sigma) has to be specified.
add  = yes                  # (optional) yes or no (default = yes)
}

Note

This profile corresponds to LSS theory (Lindhard, Scharff, Schiott theory) for doping - Gaussian distribution of ion implantation.

gaussian2D

Gaussian distribution function in two directions, constant in perpendicular direction (2D or 3D only)

Example

gaussian2D{                     # Gaussian distribution function in two directions, constant in perpendicular direction (2D or 3D only)
rate    = 1.0e18            # maximum of generation rate [1/cm3s]
dose    = 1.0               # dose of implant [cm-1] (integrated density of 2D gaussian function)
# Either rate or dose has to be specified, but not both simultaneously.
x       = 50.0              # x coordinate of Gauss center [nm]
sigma_x = 5.0               # root mean square deviation in x direction [nm]
y       = 50.0              # y coordinate of Gauss center [nm]
sigma_y = 5.0               # root mean square deviation in y direction [nm]
z       = ...               # (3D only)
sigma_z = ...               #
# Exactly two out of x, y, z and the appropriate standard deviations (sigma) have to be specified.
add  = yes                  # (optional) yes or no (default = yes)
}

gaussian3D

Gaussian distribution function in three directions (3D only)

Example

gaussian3D{                     # Gaussian distribution function in three directions (3D only)
rate    = 1.0e18            # maximum of generation rate in [1/cm3s]
dose    = 1.0               # dose of implant [dimensionless] (integrated density of 3D gaussian function)
x       = 50.0              # x coordinate of Gauss center [nm]
sigma_x = 5.0               # root mean square deviation in x direction [nm]
y       = 50.0              # y coordinate of Gauss center [nm]
sigma_y = 5.0               # root mean square deviation in y direction [nm]
z       = 50.0              # z coordinate of Gauss center [nm]
sigma_z = 5.0               # root mean square deviation in z direction [nm]
# All three x, y, z and the appropriate standard deviations (sigma) have to be specified.
add  = yes                  # (optional) yes or no (default = yes)
}

import

import generation profile from external file

import{                                           # import generation profile from external file.
import_from = "import_generation_profile"     # reference to imported data in import{}. The file being imported must have exactly one data component.
}

### Remove¶

It is also possible to remove a generation rate from a specific region.

remove{}
structure{
region{
generation{ remove{} }             # remove generation rate from this region, to keep certain regions free from generation rate.
}    # region
}       # structure

Note

doping{} and generation{} is always additive per default (add = yes) (unless import is different), i.e. each profile adds to the already existing dopants/fixed charges/generation at a given point. At the same time, using remove{}, all species of the already existing doping or generation concentrations can be removed. However, there is also the problem that remove{} removes all species of dopants/fixed charges at a given point. Thus, removing e.g. only donors but not acceptors is difficult. This problem is solved by the new “add = yes/no” flag, which the user can specify for each profile (and thus for the species of that profile), whether the profile should add to (which is the default) or replace the already existing concentration of the profile species.

For import{}, this flag has not been implemented yet.

## Example¶

### 3D¶

Figure 2.2.5 shows a 3D generation profile that is defined inside a 20 nm x 20 nm x 50 nm cube where the 50 nm are the z direction. The generation rate profile is homogeneous with respect to the (x,y) plane, it only varies along the z direction.

Figure 2.2.5 Three-dimensional generation rate profile. (Image generated by Paraview.)

The generation rate profile is constant between z = 10 nm and z = 25 nm with a rate of 1 x 1018 $$[1/(cm^3s)]$$. It has Gaussian shape from z = 25 nm to z = 45 nm (gaussian1D). It is zero between z = 0 nm and z = 10 nm, as well as between z = 45 nm and z = 50 nm.

 z = 0 ~ 10 nm z = 10 ~ 25 nm z = 25 ~ 45 nm z = 45 ~ 50 nm generation rate $$[1/(cm^3s)]$$ 0.0 constant (1.0 × 1018) Gaussian (center = 25nm, $$\sigma_z=6.0$$ nm) 0.0

Here is the structure part of the input file that generates the above generation profile. The whole input file is available here.

structure{
output_generation{}             # output generation rate for each grid point in units of [10^18/(cm3 s)]

region{                         # default material
everywhere{}
binary{ name = GaAs }
contact{ name = contact }
}
region{
binary{ name = GaAs }
cuboid{
x = [0E0, 20E0]
y = [0E0, 20E0]
z = [0E0, 10E0]
}
}
region{
binary{ name = GaAs }
cuboid{
x = [0E0, 20E0]
y = [0E0, 20E0]
z = [10E0, 25E0]
}
generation{
constant{
rate = 1.0E18       # generation rate [1/cm3s] (applies to 1D, 2D and 3D)
}
}
}
region{
binary{ name = GaAs }
cuboid{
x = [0E0, 20E0]
y = [0E0, 20E0]
z = [25E0, 45E0]
}
generation{
gaussian1D{
rate = 1.0E18       # maximum of generation rate [1/cm3s]
z = 25              # z coordinate of Gauss center (ion's projected range Rp, i.e. the depth where most ions stop) [nm]
sigma_z = 6.0       # root mean square deviation in z direction (statistical fluctuation of Rp) [nm]
}
}
}
}<>