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

The Fermi-Dirac function, represented by a sigmoid curve, indicates the probability of an energy state being occupied by an electron at a given temperature.
The Fermi level represents the energy state with a 50 percent occupancy probability and lies between the valence and conduction bands.
At absolute zero, energy states up to the Fermi level are filled, while those above are empty. At higher temperatures, states above the Fermi level may be filled.
In intrinsic semiconductors, equal concentrations of holes and electrons imply that the Fermi level lies in the middle of the band gap.
In n-type semiconductors, a higher electron concentration shifts the Fermi level close to the conduction band.
In p-type semiconductors, the Fermi level lies near the valence band, due to a higher hole concentration.
As temperature increases, more electrons transition from the valence to the conduction band, moving the Fermi level closer to the conduction band.
When materials with different Fermi levels connect, electrons flow from the higher Fermi level to the lower one to align the Fermi levels at the junction to establish equilibrium.

fermi-niveau

De Fermi-Dirac-functie wordt weergegeven door een S-vormige curve die de waarschijnlijkheid aangeeft dat een energietoestand bij een bepaalde temperatuur door een elektron wordt ingenomen. Het Fermi-niveau is het energieniveau waarbij er vijftig procent kans is om een ​​elektron te vinden, en bevindt zich tussen de valentieband met lagere energie en de geleidingsband met hogere energie.

 Bij het absolute nulpunt vullen elektronen alle energietoestanden tot aan het Fermi-niveau, waardoor de bovenste toestanden leeg blijven. Naarmate de temperatuur stijgt, neemt de energie van elektronen toe en kunnen ze de lege toestanden boven het Fermi-niveau bezetten.
 
In intrinsieke halfgeleiders, waar de concentratie van elektronen en gaten gelijk is, bevindt het Fermi-niveau zich in het midden van de bandafstand. Dit verandert wanneer onzuiverheden worden toegevoegd om halfgeleiders van het n-type of het p-type te creëren. In n-type halfgeleiders, met een teveel aan elektronen, verschuift het Fermi-niveau dichter naar de geleidingsband. Omgekeerd, in halfgeleiders van het p-type, waar er een hogere concentratie gaten is, beweegt het Fermi-niveau dichter naar de valentieband.
De temperatuurstijging leidt ertoe dat grotere hoeveelheden elektronen de sprong maken van de valentieband naar de geleidingsband, waardoor het Fermi-niveau in de richting van de geleidingsband wordt geduwd. Deze verschuiving beïnvloedt de geleidbaarheid van de halfgeleider.
Wanneer materialen met verschillende Fermi-niveaus in contact komen, stromen elektronen van het gebied met hogere Fermi-niveaus naar het lagere. De beweging van elektronen lijnt de Fermi-niveaus op de kruising uit, waardoor een evenwicht ontstaat. Dit concept speelt een cruciale rol bij de werking van talrijke elektronische componenten, waardoor de regulering en aanpassing van de elektrische geleidbaarheid en de prestaties van elektronische apparaten mogelijk wordt.

Fermi-niveau

The Fermi-Dirac function, represented by a sigmoid curve, indicates the probability of an energy state being occupied by an electron at a given ...

Education

JoVE Core

Electrical Engineering

Elektrotechniek

Unit 1

Basics of Semiconductors

Basis van halfgeleiders

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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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p-n junction

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biasing of p-n junction

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metal-semiconductor junctions

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Biasing metal-semiconductor junctions means applying a voltage across the junction. The metal connects to the voltage source, and the semiconductor is grounded. This setup helps control the direction and size of current in devices such as diodes, transistors, and photovoltaic cells. In a Schottky junction with an n-type semiconductor, a positive voltage on the metal lowers its Fermi level. A Fermi level is the energy level that helps describe how electrons are distributed. Lowering this level...

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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key terms and concepts

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

Fermi Level in Semiconductors | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Fermi Level in Semiconductors

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