Semiconductor Module Updates

For users of the Semiconductor Module, COMSOL Multiphysics® version 6.0 includes functionality for transition between discrete trap energy levels, the ability to add contact resistance to metal contacts, and new heterojunction heat source functionality for thermal modeling. Read more about the Semiconductor Module updates below.

Transition Between Discrete Levels

A new Transition Between Discrete Levels feature is available as an attribute to the three trap-assisted recombination features (domain, boundary, and heterointerface) when the explicit trap option is selected and more than one discrete trap energy levels are created. This feature allows you to specify the decay lifetime between the trap levels and to simulate the transition between the quantized levels of quantum wells and/or quantum dots by treating them as trap levels. You can view this new feature in the A Solar Cell with InAs Quantum Dots Embedded in AlGaAs/GaAs Quantum Wells tutorial model.

A closeup view of the COMSOL Multiphysics UI showing the Model Builder with the Transition Between Discrete Levels node highlighted, the corresponding Settings window, and 1D plot in the Graphics window.
A solar cell model using the new transition feature to model the transition between the comprising quantum well and quantum dots.

Contact Resistance

A new Contact resistance option has been added to the Metal Contact boundary condition for both Ohmic and Schottky contact types and all five driving modes: voltage, current, power, circuit current, and circuit voltage. This feature can be enabled by selecting the Contact resistance check box (disabled by default) in the Settings window. This allows more realistic and convenient modeling of metal contacts. The A Cross-Bridge Kelvin Resistor Model for the Extraction of Specific Contact Resistivity tutorial model shows this new option.

A cross-bridge Kelvin resistor model showing the electric potential in the Prism color table and the current density shown in arrows and streamlines.
Electric potential (color) and current density (arrows and streamlines) of a cross-bridge Kelvin resistor for contact resistance measurement.

Klaassen Unified Mobility Model (LIC)

The Semiconductor interface now includes a Klaassen Unified Mobility Model feature (sometimes referred to as Philips unified mobility model) available through the Semiconductor Material Model node. In this model, the total carrier mobility is given by combining the lattice (L), donor (I), acceptor (I), and carrier–carrier (C) scattering effects. This mobility model also includes the screening of impurities by charge carriers and clustering of impurities at high doping levels. Both the Trench-Gate IGBT 3D and Trench-Gate IGBT 2D tutorial models show this new functionality.

A 3D trench-gate IGBT model showing the electron concentration in the Prism color table and current streamlines.
A model of an IGBT incorporating the Klaassen Unified Mobility Model feature.

Heterojunction Heat Source

The Joule heating contribution to the boundary heat sources at heterojunctions has been included in the built-in variables of the Semiconductor interface. This makes it easier to perform coupled thermal analysis of heterostructures.

New Default Solver

A new physics-suggested solver sequence has been added to the Semiconductor interface to streamline the study setup for models with field-dependent mobility and/or impact ionization generation. These existing Application Library models are now more efficient with the new solver sequence:

Reuse of Solution for Parametric Eigenvalue Problems

It is now possible to select the start vectors when solving parametric eigenvalue problems. This functionality can save computational time for eigenvalue problems with solutions that are smoothly varying with a change in the parameter. Examples can be found in models that use the Schrödinger-Poisson interface. With the Eigenvalue search method set to Manual, you can often reduce the number of iterations by at least 50%.

Trapping Features

A new option to specify additional electron and hole capture rates has been added to the Discrete Energy Level attribute for the trap-assisted recombination features (domain, boundary, and heterointerface), when the explicit trap option is selected. The Continuous Energy Levels feature has been enhanced by expanding the range of the trap energy levels outside of the band gap and allowing the capture probability to depend on the trap energy level. The trapping feature for the density-gradient formulation has been enhanced with the new option of solving for the trap occupancy (as opposed to the trap Fermi level).

Mobility Models

The Caughey-Thomas Mobility Model has been enhanced with several new options for the formulation of the driving forces, adding versatility for users interested in different types of driving forces.

Metal Contacts

A new built-in global variable for the average terminal current density has been added for the Metal Contact boundary condition, making it convenient to obtain scaling-independent output quantities for comparison purposes.

New and Updated Tutorial Models

COMSOL Multiphysics® version 6.0 brings several new and updated tutorial models to the Semiconductor Module.