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sandakelum
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In a semiconductor @ 0k highest energy state lie on fermilevel(all electrons @ valence band). but @ room temperature highest energy state of covelence band lie below the fermilevel. how can i understand this? pls help me.
sandakelum said:In a semiconductor @ 0k highest energy state lie on fermilevel(all electrons @ valence band). but @ room temperature highest energy state of covelence band lie below the fermilevel. how can i understand this? pls help me.
Found hereThe central task of basic semiconductor physics is to establish formulas for the position of the Fermi level EF relative to the energy levels EC and E
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and causes the Fermi level EF to shift
nasu said:What is your definition of Fermi level for semiconductors?
Note that according to the common use, the "Fermi level" in semiconductors is in the band gap. This is because what is called Fermi level in semiconductors is actually the chemical potential.
Even if you stick with the definition used for metals, Fermi level is the maximum energy level occupied at zero K. So it does not change with temperature, by definition.
The chemical potential is what changes with temperature.
A semiconductor is a type of material that has electrical conductivity between that of a conductor and an insulator. This means that it can conduct electricity, but not as well as a metal. Examples of semiconductors include silicon, germanium, and gallium arsenide.
At 0K (absolute zero), a semiconductor is in its lowest energy state and all of the electrons are in the valence band. At room temperature, some electrons have enough thermal energy to jump from the valence band to the conduction band, creating both holes (positively charged) and free electrons (negatively charged).
The band gap is the energy difference between the valence and conduction bands in a semiconductor. A larger band gap means that more energy is required for electrons to jump from the valence band to the conduction band, resulting in fewer free electrons and holes at room temperature.
Understanding the electronic states of a semiconductor at different temperatures is important for designing and optimizing electronic devices. At 0K, a semiconductor behaves differently than at room temperature, and this knowledge can be used to improve device performance.
Impurities, or dopants, can be added to a semiconductor to change its electronic properties. For example, adding a pentavalent dopant, such as phosphorus, creates extra free electrons in the conduction band, making the semiconductor more conductive. Alternatively, adding a trivalent dopant, such as boron, creates extra holes in the valence band, making the semiconductor less conductive.