Name: fermi level in semiconductors
Uploaded: 2024-07-08T13:20:09.000Z
Duration: 1 min 18 s
Channel: JoVE

La fonction de Fermi-Dirac, représentée par une courbe sigmoïde, indique la probabilité qu’un état d’énergie soit occupé par un électron à une température donnée.
Le niveau de Fermi représente l’état d’énergie avec une probabilité d’occupation de 50 % et se situe entre les bandes de valence et de conduction.
Au zéro absolu, les états d’énergie jusqu’au niveau de Fermi sont remplis, tandis que ceux au-dessus sont vides. À des températures plus élevées, les états supérieurs au niveau de Fermi peuvent être remplis.
Dans les semi-conducteurs intrinsèques, des concentrations égales de trous et d’électrons impliquent que le niveau de Fermi se trouve au milieu de la bande interdite.
Dans les semi-conducteurs de type n, une concentration d’électrons plus élevée déplace le niveau de Fermi près de la bande de conduction.
Dans les semi-conducteurs de type p, le niveau de Fermi se situe près de la bande de valence, en raison d’une concentration de trou plus élevée.
À mesure que la température augmente, davantage d’électrons passent de la valence à la bande de conduction, rapprochant le niveau de Fermi de la bande de conduction.
Lorsque des matériaux avec des niveaux de Fermi différents se connectent, les électrons circulent du niveau Fermi supérieur vers le niveau inférieur pour aligner les niveaux Fermi à la jonction afin d’établir l’équilibre.

niveau de fermi

La fonction de Fermi-Dirac est représentée par une courbe en forme de S, indiquant la probabilité qu'un état énergétique soit occupé par un électron à une température donnée. Le niveau de Fermi est le niveau d'énergie auquel il y a cinquante pour cent de chances de trouver un électron, et il se situe entre la bande de valence d'énergie inférieure et la bande de conduction d'énergie supérieure.
À température de zéro absolu, les électrons remplissent tous les états énergétiques jusqu’au niveau de Fermi, laissant les états supérieurs vides. À mesure que la température augmente, l’énergie des électrons augmente, et ils deviennent capables d’occuper les états vacants au-dessus du niveau de Fermi.
Dans les semi-conducteurs intrinsèques, où la concentration d’électrons et de trous est égale, le niveau de Fermi est situé au milieu de la bande interdite. Ceci est modifié lorsque des impuretés sont ajoutées pour créer des semi-conducteurs de type n ou de type p. Dans les semi-conducteurs de type n, avec un excès d’électrons, le niveau de Fermi se rapproche de la bande de conduction. À l’inverse, dans les semi-conducteurs de type p, où la concentration de trous est plus élevée, le niveau de Fermi se rapproche de la bande de valence.
L’augmentation de la température conduit à un plus grand nombre d’électrons passant de la bande de valence à la bande de conduction, poussant ainsi le niveau de Fermi vers la bande de conduction par ce processus. Ce décalage affecte la conductivité du semi-conducteur.
Lorsque des matériaux présentant des niveaux de Fermi différents entrent en contact, les électrons circulent de la région des niveaux de Fermi supérieurs vers la région inférieure. Le mouvement des électrons aligne les niveaux de Fermi aux jonctions, établissant ainsi un équilibre. Ce concept joue un rôle crucial dans le fonctionnement de nombreux composants électroniques, permettant la régulation et l'ajustement de la conductivité électrique et les performances des appareils électroniques.

Niveau de Fermi

La fonction de Fermi-Dirac, représentée par une courbe sigmoïde, indique la probabilité qu’un état d’énergie soit occupé par un électron à une ...

Education

Enseignement

JoVE Core

Electrical Engineering

Génie électrique

Unit 1

Unité 1

Basics of Semiconductors

Les bases des semi-conducteurs

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

Fermi Level

fermi level in semiconductors

The Fermi level is a key energy level in semiconductors. It sits between the lower-energy valence band and the higher-energy conduction band. The Fermi-Dirac function, which follows an S-shaped curve, shows the chance that an energy state is filled by an electron at a given temperature.

At absolute zero, electrons occupy every energy state up to the Fermi level. States above it stay empty. As temperature rises, electrons gain energy and can move into vacant states above the Fermi level.

In an intrinsic semiconductor, the number of electrons equals the number of holes. A hole is the missing electron state left in the valence band. In this case, the Fermi level lies near the middle of the band gap. Adding impurities changes this balance and creates n-type or p-type semiconductors.

In an n-type semiconductor, extra electrons shift the Fermi level closer to the conduction band. In a p-type semiconductor, a higher number of holes moves the Fermi level closer to the valence band. Higher temperature also lets more electrons jump from the valence band to the conduction band, which nudges the Fermi level toward the conduction band and changes conductivity.

When materials with different Fermi levels touch, electrons flow from the region with the higher Fermi level to the region with the lower one. This movement continues until the Fermi levels align at the junction. The resulting equilibrium is important for many electronic components because it helps control electrical conductivity and device performance.

Fermi Level in Semiconductors

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metal-semiconductor junctions

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fermi level

The Fermi level is a key energy level in semiconductors. It sits between the lower-energy valence band and the higher-energy conduction band. The Fermi-Dirac function, which follows an S-shaped curve, shows the chance that an energy state is filled by an electron at a given temperature. At absolute zero, electrons occupy every energy state up to the Fermi level. States above it stay empty. As temperature rises, electrons gain energy and can move into vacant states above the Fermi level. In an...

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Learn how the Fermi level changes with temperature, doping, and semiconductor type, and how it affects electron flow, equilibrium, and conductivity.

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electrical engineering

Fermi Level in Semiconductors

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