Why does the effective mass have two different values? Like Si(Silicon) has electron effective mass for density of state calculation:1.08 m0 and for conductivity calculation:0.26 m0.
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this is due to the anisotropy of the band structure ; this anisotropy is "felt" differently by density of states and conductivity and results in a different "effective mass", "effective" means that a complex behaviour is to be summed up in one quantity, therefore assuming a "virtual" equivalent isotropic structure and finding the isotropic structure that would mimic the anisotropic behaviour in the closest way ; it is therefore no wonder that mimicking different behaviours (density of states, conductivity) result in two different "closest isotropic virtual material"
this is explained here (with the equations)
http://ecee.colorado.edu/~bart/book/book/chapter2/pdf/ch2_3_7.pdf
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this is due to the anisotropy of the band structure ; this anisotropy is "felt" differently by density of states and conductivity and results in a different "effective mass", "effective" means that a complex behaviour is to be summed up in one quantity, therefore assuming a "virtual" equivalent isotropic structure and finding the isotropic structure that would mimic the anisotropic behaviour in the closest way ; it is therefore no wonder that mimicking different behaviours (density of states, conductivity) result in two different "closest isotropic virtual material"
this is explained here (with the equations)
http://ecee.colorado.edu/~bart/book/book/chapter2/pdf/ch2_3_7.pdf
.
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