Electron Effective Mass and Effective Mass Theory in Semiconductors

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Discussion Overview

The discussion revolves around the concept of electron "effective mass" in semiconductors, its usefulness, and the "effective mass theory" used for calculating energies related to shallow defects. Participants explore the implications of effective mass on properties like mobility and the challenges in applying this theory to deep defects.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants inquire about the introduction of effective mass in semiconductors and its usefulness, particularly in relation to properties like mobility.
  • One participant mentions that effective mass allows for the simplification of many-body interactions into a "quasiparticle" framework within Fermi Liquid Theory.
  • Another participant suggests that effective mass enables the treatment of electrons in semiconductors similarly to electrons in a vacuum.
  • There is a mention of the relationship between effective mass and orbital overlap in simple metals, where strong overlap leads to free electron-like behavior while reduced overlap increases effective mass.

Areas of Agreement / Disagreement

Participants express various perspectives on the usefulness and implications of effective mass, but no consensus is reached on the specific limitations of effective mass theory regarding deep defects.

Contextual Notes

Some assumptions regarding the applicability of effective mass theory to different types of defects remain unresolved, and the discussion does not clarify the specific conditions under which effective mass is valid.

mendes
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I would like to ask about the reason why the electron "effective mass" was introduced in semiconductors. What is its' usefulness ?

And also about the so-called "effective mass theory" used to calculate energies for the shallow defects in semiconducors. What are mean pecularities and approximations of this theory and why we can't use it to calculate deep defects.

Thanks.
 
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mendes said:
I would like to ask about the reason why the electron "effective mass" was introduced in semiconductors. What is its' usefulness ?

Er.. there are many properties that depends on the effective mass. The mobility is one example. So that's one reason why such a concept was introduced.

Another reason is that, within the Fermi Liquid Theory, we can lump all the many-body interactions into this "renormalized" mass (effective mass), creating a "quasiparticle", rather than a bare electron. This allows us to go from a many-body problem (difficult), to many one-body problem (easier).

Zz.
 
Simply because you can behave electrons in semiconductors like in electrons in vacuum with effective mass.
 
in simple metals, the effective mass can be related to the orbital overlap. strongly overlapping orbitals give states with free electron like character, whereas a reduced overlap increases the effective mass..
 

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