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qcl:advanced_settings [2022/03/30 15:59] thomas.grange |
qcl:advanced_settings [2022/03/30 16:36] (current) thomas.grange [Definition of graded alloy and graded interfaces] |
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| === Linearly graded alloys === | === Linearly graded alloys === | ||
| - | To define a linear graded alloy profile, two materials first need to be defined. | + | To define a linear graded alloy profile, two materials first need to be defined in the ''<Material>'' section |
| + | For example, | ||
| + | <code> | ||
| + | <Material> | ||
| + | <Name>GaAs</Name> <!-- Binary material --> | ||
| + | <Alias>mat1</Alias> | ||
| + | <Effective_mass_from_kp_parameters>yes</Effective_mass_from_kp_parameters> | ||
| + | </Material> | ||
| + | |||
| + | <Material> | ||
| + | <Name>Al(x)Ga(1-x)As</Name> <!-- Ternary material --> | ||
| + | <Alloy_Composition>0.15</Alloy_Composition> <!-- alloy composition x --> | ||
| + | <Alias>mat2</Alias> | ||
| + | <Effective_mass_from_kp_parameters>yes</Effective_mass_from_kp_parameters> | ||
| + | </Material> | ||
| + | </code> | ||
| + | |||
| + | Then, in the layer definition (named ''<Superlattice>''), the following can be used to define a layer with a linear alloy profile, with composition starting from the material "mat1" and ending with the material "mat2" composition. | ||
| + | <code> | ||
| + | <Layer> <!-- all the material parameters will be linearily interpolated between <Material1> and <Material2> --> | ||
| + | <Material1>mat1</Material1> | ||
| + | <Material2>mat2</Material2> | ||
| + | <Thickness unit="nm">5.0</Thickness> | ||
| + | </Layer> | ||
| + | </code> | ||
| + | |||
| + | |||
| + | === Graded interfaces === | ||
| + | |||
| + | To specify a grading for all the interfaces of the structure, the following command ''<InterfaceWidth>'' has to be included in the ''<Interface_Roughness>'' section. | ||
| + | <code> | ||
| + | <Interface_Roughness> | ||
| + | <InterfaceWidth unit="nm">0.8</InterfaceWidth> | ||
| + | ... | ||
| + | </Interface_Roughness> | ||
| + | </code> | ||
| + | In this case, the alloy profile of the all strucure is convoluted by a Gaussian. For a well defined interface, this results in an error function profile of the form: | ||
| + | $$ | ||
| + | c(z) = c_0 + d_0 \text{erf} \left[2 | ||
| + | \sqrt{ln(2)}(z − z_0)/L \right] | ||
| + | $$ | ||
| + | where $L$ is the quantity specified in ''<InterfaceWidth>''. | ||
| ==== Scattering processes ==== | ==== Scattering processes ==== | ||
qcl/advanced_settings.1648655977.txt.gz · Last modified: 2022/03/30 15:59 by thomas.grange
