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3D InSb FET |
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A simple 3D InSB/Al0.2In0.8Sb FET has been simulated by means of Aeneas in order to test its capabilities and reliability.
This device can be seen as a simple InSb layer sandwitched between two InSB/Al0.2In0.8Sb layers. In the upper surface, we find the source, drain and gate contacts. This InSB/Al0.2In0.8Sb FET has a simple p-n-p structure with a channel lenght equal to 0.12 micron (in x-direction) x 3.0 micron (in z-direction). The MESFET has two p regions of 0.12 micron and 0.5 micron respectively. The doping regions are p=1.e22/m^3 and n=1.e23/m^3. The applied voltages are equal to 1.0 Volt (for the drain contact), -0.2 Volt (for the gate contact) and -0.5 (for the bulk contact).
The devices is defined by means of an input file which describes the doping regions, the boundary conditions, the applied voltage, the number of simulated particles and so on. Furthermore, a mesh file describes the diode shape. The input ASCII file is reported at the end of this page, while various 3D pictures obtained using Aeneas are shown in the following.
Please, note that the Monte Carlo simulation is coupled consistently to a tetrahedra mesh, which is a great advantage for novel 3D semiconductor device simulations.
The mesh is introduced by means of an ASCII file described the dimensions and geometry (in MESH format).
It is possible to see, from the videos in the devices section that this kind of FET (which is similar to a InSb depletion FET) is very well simulated by Aeneas. It is, in fact, possible to study the real-time dynamics of the electrons moving in such a device.
For example, from the video "electrons in potential" it is possible to extract the following insights:
- In a first moment the number of particles slightly increases, due to the bulk contact which has an applied potential equal to -0.5 Volt. This, basically, pushes the electrons to the upper part of the devices (such that electrons are unable to go out from the lower Schottky contact, they do not have enough energy) while electrons come into the devices through the upper Ohmic contacts (source and drain).
- In a second moment the number of particles decreases because of the electric field which pushes the particles in the direction from the drain contact to the source one (see the following picture about velocity).
- The electrostatic potential (along with the dynamical features of the particles) reaches very quickly a stationary state (after less than 3.00 picoseconds).
This informations could be obtained with a simple mesh of about 16000 tetrahedra and starting with about 500.000 particles. It is, obviously, possible to obtain more detailed informations (such as the current density and conservation) running a further simulation with more tetrahedra and more particles.
The following picture reports the final velocity of the electrons, after reaching the stationary state.
The following picture reports the particles in the stationary electrostatic potential.
This last picture reports the stationary electrostatic potential.
We report, now, the input file used bu Aeneas, in order to obtain the above described results.
# creation : 18 june 2007, J.M.
Sellier
# last modified : 03 august 2007, J.M. Sellier
# this is the simulation of a InSB/AlInSb FET (for Intel)
# load the input mesh file
LOADMESH InSb_FET.mesh
# read the neighbourhood table
NEIGHBOURHOODTABLE READ
# include impact ionization
IMPACTIONIZATION NO
# updating Poisson equation every time step
POISSONUPDATE YES
# time step in seconds
TIMESTEP 0.0015e-12
# final time of simulation in seconds
FINALTIME
2.25e-12
# the code starts the mean average for velocity
# and energy at the last MEDIA time steps
MEDIA 500
# lattice temperature in Kelvin
LATTICETEMPERATURE
300.
# save the data every number of steps
SAVEEVERYNUMSTEPS
75
# impurity density in 1/m^3
CIMP 1.e14
# contact type and applied voltage (meters, volts)
CONTACT X 0.0
0.75e-6 Y
0.0 1.0e-6 Z
0.74e-6 0.74e-6 OHMIC
0.0
CONTACT X 2.25e-6 3.0e-6
Y 0.0 1.0e-6 Z
0.74e-6 0.74e-6
OHMIC 1.0
CONTACT X
1.0e-6 2.0e-6 Y
0.0 1.0e-6 Z
0.74e-6 0.74e-6
SCHOTTKY 0.2
CONTACT X 0.0e-6 3.0e-6
Y 0.0 1.0e-6 Z
0.0 0.0
SCHOTTKY -0.5
# statistical weight, i.e. the number of particles
in cell
# which have the maximum density value
STATISTICALWEIGHT
180
# the Poisson solver can be 1, 2, 3 or 4.
# it is used to select the method for solving the Poisson equation
POISSONSOLVER
4
# the tollerance for the Poisson solver
POISSONTOLLERANCE
1.e-16
# maximum number of iterations for the Poisson
solver
POISSONITMAX
1500
# material specification (Si is the default)
MATERIAL X 0.0
3.0e-6 Y 0.0
1.0e-6 Z 0.0
0.5e-6 ALxIN1-xSB
0.2
MATERIAL X 0.0 3.0e-6
Y 0.0 1.0e-6
Z 0.5e-6 0.62e-6
INSB
MATERIAL X 0.0 3.0e-6
Y 0.0 1.0e-6
Z 0.62e-6 0.74e-6
ALxIN1-xSB 0.2
# donor density of the device in 1./m^3
ACCEPTORDENSITY X
0.0 3.0e-6 Y
0.0 1.0e-6 Z
0.0 0.5e-6 1.e22
ACCEPTORDENSITY X
0.0 3.0e-6 Y
0.0 1.0e-6 Z
0.62e-6 0.74e-6 1.e22
DONORDENSITY X 0.0 3.0e-6
Y 0.0 1.0e-6 Z
0.5e-6 0.62e-6 1.e23
# quantum effective potential taken into
account
NOQUANTUMEFFECTS
# what we save in which format
SAVEPARTICLES YES POINT3D
SAVEFIELDS YES VTK
# end of input file