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

La función de Fermi-Dirac, representada por una curva sigmoidea, indica la probabilidad de que un estado de energía esté ocupado por un electrón a una temperatura dada.
El nivel de Fermi representa el estado de energía con una probabilidad de ocupación del 50 por ciento y se encuentra entre las bandas de valencia y conducción.
En el cero absoluto, los estados de energía hasta el nivel de Fermi se llenan, mientras que los superiores están vacíos. A temperaturas más altas, se pueden llenar los estados por encima del nivel de Fermi.
En los semiconductores intrínsecos, concentraciones iguales de huecos y electrones implican que el nivel de Fermi se encuentra en el medio de la banda prohibida.
En los semiconductores de tipo n, una mayor concentración de electrones desplaza el nivel de Fermi cerca de la banda de conducción.
En los semiconductores de tipo p, el nivel de Fermi se encuentra cerca de la banda de valencia, debido a una mayor concentración de huecos.
A medida que aumenta la temperatura, más electrones pasan de la banda de valencia a la banda de conducción, acercando el nivel de Fermi a la banda de conducción.
Cuando los materiales con diferentes niveles de Fermi se conectan, los electrones fluyen desde el nivel de Fermi superior al inferior para alinear los niveles de Fermi en la unión y establecer el equilibrio.

nivel de fermi

La función de Fermi-Dirac está representada por una curva en forma de S que indica la probabilidad de que un electrón ocupe un estado energético a una temperatura determinada. El nivel de Fermi es el nivel de energía en el que hay un cincuenta por ciento de posibilidades de encontrar un electrón y se ubica entre la banda de valencia de menor energía y la banda de conducción de mayor energía.
A la temperatura del cero absoluto, los electrones llenan todos los estados de energía hasta el nivel de Fermi, dejando los estados superiores vacíos. A medida que aumenta la temperatura, aumenta la energía de los electrones y estos se vuelven capaces de ocupar los estados vacantes por encima del nivel de Fermi.
En los semiconductores intrínsecos, donde la concentración de electrones y huecos es igual, el nivel de Fermi se sitúa en el medio de la banda prohibida. Esto se altera cuando se añaden impurezas para crear semiconductores de tipo n o de tipo p. En los semiconductores de tipo n, con un exceso de electrones, el nivel de Fermi se acerca a la banda de conducción. Por el contrario, en los semiconductores tipo p, donde hay una mayor concentración de huecos, el nivel de Fermi se acerca a la banda de valencia.
El aumento de temperatura hace que un mayor número de electrones salten de la banda de valencia a la banda de conducción, empujando el nivel de Fermi hacia la banda de conducción en el proceso. Este cambio afecta la conductividad del semiconductor.
Cuando materiales con diferentes niveles de Fermi entran en contacto, los electrones fluyen desde la región de niveles de Fermi más altos a la región más baja. El movimiento de los electrones alinea los niveles de Fermi en la unión, estableciendo un equilibrio. Este concepto juega un papel crucial en el funcionamiento de numerosos componentes electrónicos, permitiendo la regulación y ajuste de la conductividad eléctrica y el rendimiento de los dispositivos electrónicos.

Nivel de Fermi

La función de Fermi-Dirac, representada por una curva sigmoidea, indica la probabilidad de que un estado de energía esté ocupado por un electrón en un momento dado.

Education

Educación

JoVE Core

Electrical Engineering

Ingeniería Eléctrica

Unit 1

Unidad 1

Basics of Semiconductors

Conceptos básicos de los semiconductores

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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

energy bands in solids

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semiconductors

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types of semiconductors

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carrier generation and recombination

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carrier transport

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Drift and diffusion are the two main ways electric current forms in semiconductors. These charge-carrier motions help determine how semiconductor devices work and how well they perform. The carriers involved are electrons and holes. Drift current begins when an external electric field acts on charge carriers. Electrons and holes move between collisions with lattice atoms, and this motion creates drift velocity. For electrons, drift velocity depends on electron mobility and the electric field...

p-n junction

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A p-n junction forms when p-type and n-type semiconductor materials are joined together. At the boundary, holes from the p-side and electrons from the n-side diffuse into the opposite side because of the concentration gradient. This movement leaves a region with no free charge carriers near the junction, called the depletion region. The charge density in the depletion region can be described on the n-side and p-side using the donor and acceptor doping concentrations, ND and NA. The fixed...

biasing of p-n junction

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metal-semiconductor junctions

Schottky and Ohmic Metal Contacts

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biasing of 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...

fermi level dynamics

Vacuum Level and Schottky Barriers

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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.

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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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