What is the relation between electron effective mass and carrier relaxation time (or scattering or defects) in a semiconductor?

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Vesselin Donchev Popular answer

The mobility = e*relaxation time/eff.mass

(if this can help you)

Omar M S

Effective mass is the mass of election while it's velocity is relative to speed of light

larger effective mass represents a smaller velocity and vice versa

this explains higher effective mass for electrons facing larger scatering numbers of course a smaller effective mass for a less scattering points, scatering points could be defects, impurities, boundaries, ----

Arindam Mallick

Thanks for the explanation.

But I have got opposite result that of you suggested.

For higher effective mass I got lesser scattering (higher relaxation time).

Isn't it contradicting??

Tarık Ömer Oğurtanı

The relaxation time is controlled by the inelastic collisions, which means that the large linear momentum associated the heavy effective mass for a given kinetics energy (E=h2k2/2me) requires much greater numbers of collisions to transfer its kinetic energy to the targeted point and even line defects in the bulk matrix. That means heavy electron has to travel much longer distance due to multiple collision, which is also determined by the concentration of the defect centers inversely. In the case of electron -phonon interactions problem might be more complicated, but follows up the similar trend. Where h is h-bar.

Ahmed Saeed Hassanien

Dear Dr. Arindam Mallick

Have a nice day and good times

The appended paper may help you, where there are many opto-electrical parameters concerns your study have been determined.

Good luck

https://www.researchgate.net/publication/294426798_Studies_on_dielectric_properties_opto-electrical_parameters_and_electronic_polarizability_of_thermally_evaporated_amorphous_Cd50S50-xSex_thin_films

Article Studies on dielectric properties, opto-electrical parameters...

Vesselin Donchev

Jan Isberg

In deformation-potential acoustic phonon -electron scattering the relaxation time is proportional to (density-of-states effective mass)^-1.5. if the carrie.r distribution is fixed

Dear Jan,

Would you mind explaining a little bit.. in a easier way...

Thanks

Dear Vesselin Donchev:

I have found effective mass using that equation only. I would like to know some physical details... the significance of m* during carrier transport through semi conductor.

Calculated relaxation time using conductivity, and plasmon energy.

@ Ahmed Saeed Hassanien:

Thank you Sir, for the upload.

According to Einstein and Nerst the definition of mobility of a particle moving in a viscous media without acceleration any is velocity/force. By simple dimensional analysis it shows that ''as Vesselin claimed'', mobility mhu= F/V, which has the dimension of [time/mass], which means his equation is correct with a missing steric factor.

SEE: Kittel Page 230-231; Mhu= e THo/Mass (in Electrostatic FİELD)

Dear Arindam,

Concerning “the significance of m* during carrier transport through semiconductor,” I would say that this can be found in the solid state textbooks. In fact you as many others use the so called method of the effective mass. When the electron is in the periodic potential of the crystal lattice one considers the electron as a free particle but instead of m0=9.11E-31kg it has an effective mass. The latter takes into account the fact that the electron is in the crystal.