This page discusses how to set the physical parameters of the MQW solver, including:
- Carrier density (if excitons are disabled)
- Bias electric field
This page also discusses how to define the physical properties of the MQW stack, including:
- Effective index
- Linewidth broadening
- Valence band offset
How these parameters affect the simulation is described on the MQW Solver Physics page.
The temperature is set by the temperature property of the MQW solver object, found in the Parameters tab of the Edit MQW Gain Solver window.
This parameter is ignored when the exciton model is enabled, except for the dependence of material properties with temperature. Instead, a full depletion of the quantum wells is assumed (valence band full, conduction band empty).
If the exciton model is disabled the carrier density inside the MQW stack must be specified. If the exciton model is enabled the MQW solver assumes that the quantum wells are fully depleted (valence band full, conduction band empty) so the carrier density properties are disabled.
The carrier density parameters are set in the Parameters tab of the Edit MQW Gain Solver window. There are two options for specifying the carrier density: as a uniform density over the entire stack, or (if partitions are enabled) as a uniform density in each partition.
To set a uniform carrier density over the entire stack:
- Set the cden type to uniform.
- Set cden to the carrier density in units of m-3.
To set a different carrier density in each partition of a partitioned stack:
- Set the cden type to partitioned. This option will only be available if the enable partition option is selected.
- Set the values in the cden partitioned table to the carrier density in each partition in units of m-3. The cden partitioned table is numbered in the same order as the partitions in the partition layer table. For example, partition 1 in the cden partitioned table corresponds to the partition between partition layer 1 and partition layer 2 in the partition layer indices table in the Layers tab.
Bias Electric Field
There are two options for setting the electric field along the MQW stack: as a uniform field or varying as a function of position along the stack.
The bias electric field parameters are set in the Parameters tab of the Edit MQW Gain Solver window.
To set a uniform electric field over the entire stack:
- Set the efield type to uniform.
- Set efield to the electric field value in units of V/m.
To set an electric field that varies along the position in the stack:
- Set the efield type to table.
- Set the values in the potential table to the positions along the stack in microns in the x column and the corresponding electric field values at those locations in V/m in the potential Rows can be added to the table with the button and removed with the button. The field values will be linearly interpolated between the points you specify onto the simulation grid. The first layer is assumed to start at z = 0.
The effective refractive index of the MQW stack is required for the MQW solver gain calculation. This can be found using mode solvers such as FDE or FEEM. If you are modelling a 2D waveguide structure, the entire waveguide structure should be used for the effective index calculation, despite the fact that the MQW solver is 1D.
The effective index can be set using the neff property, found in the Layers tab of the Edit MQW Gain Solver window.
The linewidth broadening due to the intraband relaxation rate can be set using the gamma property, found in the Layers tab of the Edit MQW Gain Solver window. The gamma property is the full width at half maximum of a Lorentzian distribution expressed in eV.
This value can be found in the literature, or it can be modified to fit measurement results.
Valence Band Offset
The valence band offset can be automatically calculated or set manually. If possible, it is better to set the offset manually based on literature values.
To set the valence band offset automatically, disable the override band offset property on the Layers tab of the MQW solver edit dialog.
To set the valence band offset manually, on the Layers tab of the Edit MQW Gain Solver window:
- Select override band offset.
- Set the Valence Band Offset for each layer in the MQW stack in the Layers table.
For detailed information about band offsets in MQW refer to this page. The article describes the calculations used for the default band offset. It also describes the manual band override calculation and how strain is accounted in the results.
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