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qcl:faq [2021/05/07 16:14] thomas.grange |
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| $E_{\rm v,av}$ is the average energy of heavy hole (hh), light hole (lh) and split-off hole (so). | $E_{\rm v,av}$ is the average energy of heavy hole (hh), light hole (lh) and split-off hole (so). | ||
| $\Delta_{\rm so}$ is the spin-orbit split-off energy. | $\Delta_{\rm so}$ is the spin-orbit split-off energy. | ||
| + | |||
| + | These two different options have different consequences in how the temperature dependence of the bandgap is accounted. Indeed: | ||
| * Option a) Specify conduction band offset (CBO) $E_{\rm c}$\\ ''<UseConductionBandOffset>yes</UseConductionBandOffset>'' | * Option a) Specify conduction band offset (CBO) $E_{\rm c}$\\ ''<UseConductionBandOffset>yes</UseConductionBandOffset>'' | ||
| + | |||
| + | As a consequence, the band offset of the light hole becomes temperature dependent: | ||
| $$E_{\rm hh}(T) = E_{\rm c} - E_{\rm gap}(T)$$ | $$E_{\rm hh}(T) = E_{\rm c} - E_{\rm gap}(T)$$ | ||
| + | |||
| * Option b) Specify valence band offset (VBO) $E_{\rm v,av}$\\ The conduction band edge $E_{\rm c}$ is calculated and depends on temperature.\\ ''<UseConductionBandOffset>no</UseConductionBandOffset>'' (default) | * Option b) Specify valence band offset (VBO) $E_{\rm v,av}$\\ The conduction band edge $E_{\rm c}$ is calculated and depends on temperature.\\ ''<UseConductionBandOffset>no</UseConductionBandOffset>'' (default) | ||
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| However, as broadening becomes important, there will be a red shift with respect to the bare transition energies. This shift will depend on the scattering processes. So then the question of which one to trust more is also related to the question whether the parameters for scattering (interface roughness, Coulomb scattering...) matches the reality. And it should be kept in mind there are some underlying assumptions in the NEGF model (in particular the self-consistent Born approximation) which could lead to deviation with respect to reality (such as an overestimate of the is red-shifting effect of transition energy with broadening). | However, as broadening becomes important, there will be a red shift with respect to the bare transition energies. This shift will depend on the scattering processes. So then the question of which one to trust more is also related to the question whether the parameters for scattering (interface roughness, Coulomb scattering...) matches the reality. And it should be kept in mind there are some underlying assumptions in the NEGF model (in particular the self-consistent Born approximation) which could lead to deviation with respect to reality (such as an overestimate of the is red-shifting effect of transition energy with broadening). | ||
| + | |||
| + | === At zero bias, when the current asymptotically approaches 0, the current convergence factor does not converge to zero. Is this ok? === | ||
| + | |||
| + | When the current approaches 0, it is indeed normal that the current convergence factor does not goes to 0. In this case, the convergence should be checked accordingly to the other convergence factor which is based on the lesser Green’s function. | ||
qcl/faq.1620404089.txt.gz · Last modified: 2021/05/07 16:14 by thomas.grange
