Conduction and valence bands in semiconductors

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Discussion Overview

The discussion revolves around the nature of conduction and valence band states in semiconductors, specifically questioning the characterization of these states as s-type and p-type. The scope includes theoretical aspects of solid-state physics and material dependence.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions why conduction band states are considered s-type and valence band states p-type, suggesting a need for clarification.
  • Another participant challenges this characterization, indicating that it is not universally applicable and depends on the specific material and its k-space properties.
  • A further response emphasizes that the classification is material-dependent, using copper as an example where 3d electrons are involved in conduction rather than 4s electrons, which complicates the initial premise.
  • A participant cites a source that states for direct-gap semiconductors, the conduction band minimum states exhibit spherical symmetry akin to s-states, while valence band maxima states have the symmetry of p-orbitals.

Areas of Agreement / Disagreement

Participants do not reach a consensus; there are multiple competing views regarding the classification of conduction and valence band states, with some arguing for a material-dependent perspective.

Contextual Notes

The discussion highlights the limitations of generalizing the s-type and p-type classification without considering specific materials and their electronic structures.

Benevito
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Why is the conduction band state s-type and the corresponding valence band state p-type?
 
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This is not generally true. What material are you considering and where in k-space?
 
Benevito said:
Why is the conduction band state s-type and the corresponding valence band state p-type?

You really should cite where you get such a thing.

As DrDu as pointed, this is not true always and it is material dependent. For example, Cu, a common metal, has the 3d electrons as its valence shell, and thus, the 3d electrons that participate in the conduction band, not the 4s electrons. This already negates the starting point of your question.

Zz.
 
For example, here https://www3.nd.edu/~djena/kdotp.pdf it is stated that "For direct-gap semiconductors, for states near the conduction-band minimum (k = 0), the Bloch lattice-function possesses the same symmetry properties as a |S> state . In other words, it has spherical symmetry. The states at the valence band maxima , on the other hand, have the symmetry of p-orbitals"
 
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