Drift-Diffusion Solver

The ddsolver package includes drift-diffusion solver to simulate semiconductor devices. Also, Mixed-mode-system consisting of the semiconductor devices and the external components can be solved.

Salient Features

In DD-solver, coupled Poisson, electron, and hole continuity equations are solved.
Mixed-mode-system consisting of the semiconductor devices and the external components can be solved
The solver can perform quasi-stationary DC ramp, small-signal analysis, and transient analysis

Salient features - Drift-diffusion solver

The solver can perform a quasi-stationary DC ramp, small-signal analysis at a fixed DC bias, and a transient analysis.
Coupled Poisson, electron, and hole continuity equations are solved.
Mixed-mode-system consisting of the semiconductor devices and the external components can be solved coupled with drift-diffusion equations.
Physics-based models for bulk and interface mobility, recombination phenomena, traps, etc. in semiconductors available.
Model parameters are editable in the material config file, thus allowing model calibration.
Convinient Python interface can be used to perform simulations and postprocess results.

Easy-to-use Config file

Specify simulation setup in an intuitive config file.
Define active models -- region-wise, material-wise.
Set Voltage Ramps-- quasistationary, transient, small-signal.

As an illustration, a commands in the config file look as follows:

File: {Device = "FinFET_str.cfg";
       Out = "FinFET";}

Contacts: {...}

Physics*Region*RegSi: {
  Mobility: {DopingDep: { Masetti: [];}
  FieldDep: { Lombardi: []; }
  Recombination:{SRHRecombination=["DopingDep"];}
  } }

Solve: {Static*Poi:{ Coupled: ["Poisson"];}
  Quasistationary*Dr: {initstep = 1E-3; 
    Ramp: { Voltage*drain = 1.;}
    Coupled: ["Poisson","Electron"] } }

For exact commands in the config file, please refer to the user-guide and the examples therein.

Convinent Python Interface

Import meshed device and setup simulation.
Perform drift-diffusion simulations.
Retrieve data for postprocessing in Python.

Results Visualization

I-V characteristics stored in csv files.
Spatial Data stored in hdf file.
{it xdmf} script stored for visualization in {it paraview}.
TimeAverage: Stores temporal average of the data.
Doping distribution
Spatial distribution of electron currentSpatial distribution of electric field

Material Properties and Composition

Material config file is loaded at the start of the simulation.
List and edit parameters of all models.
Define composition dependence (linear and quadratic) of the parameters in semiconductor alloys, e.g. SiliconGermanium.

As an illustration, a material config file look as follows:

BandStructure: {
  BandGap: { 
    // [XFrac0, val0, ... ] 
    Chi0*Xdep = [0., 4.07,
        0.45, 3.575, 1., 3.5]; 
    Eg0*Xdep = [0., 1.424,  
       0.45, 1.985, 1., 2.17]; }
... 
  DoS: { Formula = 0;	 
    Nc300 = 2E19; Nv300 = 2E19;
    me = 0.91; mh = 0.53; } 
}

For exact material config file, please refer to the user-guide and the examples.

Small-signal Analysis

ACAnalysis: DC time(s) at which analysis is done.
Nodes: Contacts to be included in the AC analysis.
Jacobian at the bias point is used to perform small-signal analysis. Admittances and capacitances are written in the csv file.
Effect of small-signal voltage at drain on electron densityEffect of small-signal voltage at gate on electron density

Mixed-mode System Analysis

Mixed-mode Analysis solves the circuit-system containing electronic device which is connected to the external components.
System section defines external circuit and links the Device named MOS1 to it.
Illustration of a mixed-mode system

Electro-thermal simulations

Electro-thermal simulations solve Poisson and/or continuity equations with heat transport equation.
ThermalContacts act as heat-sink at a set Temperature.
In ThermalProperties, list active thermal models.
In Coupled, add Temperature to include heat equation.
Temperature distr. in Copper plate at 1VTemperature induced Copper plate conductivity variation at 1V

User-manual and examples

A detailed user-manual describes available analyses and how to perform,
physical models and their usage
Settings in a config file and their use