# Material Database Using Ansys Lumerical CHARGE — Lesson 1

The Electrical/Thermal Material Database stores the electrical and thermal properties of materials used in CHARGE simulations. Through the material database, you can also create new materials and modify their properties.

To access the Electrical/Thermal material database, click on the “Electrical and Thermal” button in the “Materials” section under the Design tab.

### Materials Properties Panel

The Electrical/Thermal Material Database consists of two main panels: the Material List on the left and the Material Properties on the right. When a material is selected from the Material List, the electronic/thermal properties, as well as the color associated with the material, is displayed on the Materials Properties panel.

1. “Add” button: Adds a new material to the Material List.

2. “Delete” button: Deletes the selected material from the Material List. A material used as a base material to create an alloy cannot be deleted.

3. “Copy” button: Creates a copy of the selected material in the Material List.

4. “Import” button: Imports materials from other simulation files (.ldev).

5. Material List: Displays all the materials stored in the simulation file. When you start a new project, the material database is populated with the default materials that came with the software installation. Any modification you make in the material database of your simulation file stays with the simulation file and won’t change the default material database. For information about modifying the default material database, please refer to the related links below.

6. Display option: Allows you to filter the materials that show up in the Material List. When the “Active only” option is checked, only materials that are used in the current simulation will be displayed. The drop-down menu on the right filters the materials by their material type (semiconductor, insulator, conductor, binary alloy, fluid). Alternatively, you can type in the material name in the text box.
7. Send to current project: Adds the selected material from the Material List to your current simulation. The “create new” option creates a new “material” in the objects tree with the properties of the selected material. The “add to existing” option adds the properties to the selected “material” from the objects tree (NOTE: the drop-down list gets populated only by “materials” [from the objects tree] that do not already have the corresponding properties added to them.

8. Color: Sets the color of the material.

9. Electronic Properties and Recombination tabs: Contain the properties of the material that will be used by the Charge solver and will be the subject of the following subsection about material models.

10. Property visualizer: A tool that can be used to visualize the changes in semiconductor properties of the selected material as a function of different parameters. This will be discussed in the following unit in detail.

### Property Visualizer

The properties of semiconductor materials such as mobility, carrier lifetimes and so on can be visualized as a function of various variables by clicking the "Visualize" button in the main window of the Electrical/Thermal Material Database after selecting the desired semiconductor material from the list. The following variables and semiconductor properties are available for visualization in the semiconductor properties visualizer dialog:

Variables

• $$T$$: Temperature in units of Kelvin ($$K$$)
• $$N$$: Doping concentration in units of $$cm^{-3}$$
• $$N_A$$: Acceptor doping concentration in units of $$cm^{-3}$$
• $$N_D$$: Donor doping concentration in units of $$cm^{-3}$$
• $$F$$: Field intensity in units of $$V/m$$
• $$x$$: Alloy fraction (only available for alloy materials)

Semiconductor properties

• $$\varepsilon_r$$: Relative dielectric permittivity
• $$E_g$$: Bandgap $$eV$$
• $$m_n$$: Effective mass of electron ($$m^*/m_0$$)
• $$m_p$$: Effective mass of hole ($$m^*/m_0$$)
• $$\mu_n$$: Electron mobility $$cm^2/V\dot s$$
• $$\mu_p$$: Hole mobility $$cm^2/V\dot s$$
• $$v_{sat,n}$$: Electron saturation velocity $$cm/s$$
• $$v_{sat,p}$$: Hole saturation velocity $$cm/s$$
• $$\tau_n$$: Electron SRH lifetime $$s$$
• $$\tau_p$$: Hole SRH lifetime $$s$$
• $$c_{opt}$$: optical capture coefficient for radiative recombination $$cm^3/s$$
• $$c_{au,n}$$: Auger recombination capture coefficient for electrons $$cm^6/s$$
• $$c_{au,p}$$: Auger recombination capture coefficient for holes $$cm^6/s$$

Each semiconductor property can be plotted as a function of one or two variables chosen in the first and second axis drop-down menu. The plot range, number of points and the scale (linear or log) for each variable can also be selected from this window. Any desired number of semiconductor properties can be chosen for a single plot by checking the name of each property in the window. To plot the selected properties, simply click the "Create Visualization" button. You can also send the selected property to the script workspace for further processing by clicking the "Send to Script" button. Once done, you can click the " Done" button to go back to the property editor window.

For example, the change in electron and hole mobility of silicon as a function of temperature can be plotted as shown below: