COMSOL Multiphysics^® 5.5 Release Highlights

Semiconductor Module Updates

For users of the Semiconductor Module, COMSOL Multiphysics^® version 5.5 includes a new density-gradient formulation, a new trap-assisted heterointerface recombination feature, and four new models. Learn more about these semiconductor features and other improvements below.

Density-Gradient Formulation

A new discretization option based on the density-gradient theory is introduced to include the effect of quantum confinement in the conventional drift-diffusion formulation. This provides an efficient alternative to other more sophisticated quantum mechanical methods, which are computationally expensive.

Results showing the electron concentration (slices), current density (arrows), and electric potential (isosurfaces) from the new 3D Density-Gradient Simulation of a Nanowire MOSFET model.

This functionality is demonstrated in three new models:

Trap-Assisted Heterointerface Recombination Feature

The new Trap-Assisted Heterointerface Recombination boundary condition is added for you to simulate the effect of interface traps at heterojunctions. It is straightforward to set up discrete and/or continuous energy level traps to account for their carrier capture and charging effects on heterointerfaces.

Additional Improvements

User-defined junction current option
- A new option for the heterojunction boundary condition allows the user to specify any arbitrary current density at the junction
Trap quasi-Fermi level formulation
- A new formulation for explicit traps is introduced to use the trap quasi-Fermi level as the dependent variable for which to solve
Doping-dependent material properties
- Acceptor concentration and donor concentration are now available under the Transport branch of the Model Input lists to facilitate the construction of doping-dependent material properties
Solid Mechanics coupling
- The variable for the time derivative of the electric displacement field is updated to allow mesh deformation for coupling to solid mechanics
Schrödinger-Poisson equation
- The range of weights for the Schrödinger-Poisson multiphysics coupling is extended from 20 kT to 40 kT to cover cases with higher temperature ranges
New built-in functions
- New Fermi-Dirac functions log_FD_half_inv_an and log_FD_half_an are available and accept a full range of input arguments
Accuracy improvements for:
- Caughey-Thomas Mobility Model formulation
- Default solver settings for time-dependent studies
- Default scaling for quasi-Fermi level formulations
Bug fixes for:
- An error in the time-dependent weak term for the quasi-Fermi level formulation (since COMSOL Multiphysics^® version 5.4 update 3)
- A missing effect of explicit surface trap charges on Schottky contacts
- The boundary current density formula between two adjacent semiconductor material model features, corrected for the finite volume discretization
- The selection filter for the Zero Charge boundary condition, to not override the Axial Symmetry boundary condition