Name: p-n junction diode under bias
Uploaded: 2025-05-22T09:06:15.000Z
Duration: 1 min 16 s
Channel: JoVE

La unión p-n dentro de un LED requiere polarización externa para producir luz.
La polarización directa implica aplicar un voltaje a través de la unión p-n con el terminal positivo de la batería conectado al lado p y el terminal negativo al lado n. El voltaje aplicado se opone al potencial de unión, reduciendo el ancho de la barrera.
Este ancho de barrera reducido permite el flujo de corriente al aumentar la difusión del portador mayoritario. La corriente de difusión es mayor que la corriente de deriva y la corriente neta fluye en la dirección de avance de p a n.
Durante la difusión, la recombinación de electrones y huecos en la región de unión emite fotones, lo que hace que el LED brille.
En la polarización inversa, el terminal positivo de la batería está conectado al lado n y el negativo al lado p.
Esto evita que el LED brille a medida que el potencial aplicado se suma al potencial de unión, lo que resulta en un mayor ancho de barrera y una disminución de la difusión del portador mayoritario.
La corriente neta es la pequeña corriente de deriva obtenida debido a los portadores minoritarios.
Si el voltaje de polarización inversa excede un cierto umbral, se produce una ruptura de la unión, lo que resulta en un gran flujo de corriente.

polarización de la unión p-n

El funcionamiento de un diodo de unión p-n implica varias condiciones de polarización, incluida la polarización directa, la polarización inversa y el equilibrio.
En equilibrio, no se aplica ningún voltaje externo a través de la unión p-n. La región de agotamiento se forma en la interfaz de unión debido a la difusión de portadores, lo que deja dopantes cargados, aceptores en el lado p y donantes en el lado n. Estas cargas inmóviles crean un campo eléctrico que impide una mayor difusión de los portadores. El diagrama de bandas de energía relacionado muestra que los niveles de Fermi en ambos lados están alineados, lo que indica equilibrio. El potencial incorporado a través del cruce impide el flujo neto de portadores a través del cruce.
Cuando el diodo tiene polarización directa, el voltaje aplicado reduce el potencial de barrera y estrecha el ancho de la región de agotamiento. Como resultado, los portadores pueden cruzar fácilmente la unión y el diagrama de bandas correspondiente muestra las bandas de energía inclinándose hacia arriba, lo que indica la reducción del potencial de barrera. La corriente a través del diodo bajo polarización directa aumenta exponencialmente con el voltaje aplicado.
En polarización inversa, el voltaje externo se aplica en la dirección opuesta, ampliando la región de agotamiento, aumentando el potencial de barrera, dificultando que los portadores crucen la unión y reduciendo el flujo de corriente a una corriente de saturación inversa muy pequeña. El diagrama de bandas de energía para polarización inversa muestra las bandas inclinándose hacia abajo, lo que indica un mayor potencial de barrera. La corriente en polarización inversa es un valor constante pequeño. Está cerca de la corriente de saturación pero con el signo opuesto, reflejando el menor flujo de portadores debido a la generación térmica dentro de la región de agotamiento.

Polarización de la unión P-N

La unión p-n dentro de un LED requiere polarización externa para producir luz.
La polarización directa implica la aplicación de un voltaje a través de la unión p-n ...

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

Biasing of P-N Junction

p-n junction diode under bias

P-N junction diodes change behavior under equilibrium, forward bias, and reverse bias. In equilibrium, no external voltage is applied across the junction. Carriers diffuse at the boundary and leave behind charged dopants. Acceptors remain on the p-side, and donors remain on the n-side. These fixed charges form a depletion region and an electric field that blocks further diffusion.

The band diagram at equilibrium shows the Fermi levels on both sides aligned. That alignment means the junction is in balance. A built-in potential also exists across the junction. This potential prevents a net flow of carriers from one side to the other.

When the diode is forward biased, the applied voltage lowers the barrier potential. It also narrows the depletion region. Carriers can then cross the junction more easily. The band diagram shows the energy bands bending upward, which matches the reduced barrier.

Forward bias also causes the current to rise quickly as the applied voltage increases. The current increases exponentially with voltage. In reverse bias, the external voltage is applied in the opposite direction. The depletion region widens, the barrier potential increases, and carrier flow becomes very small.

The reverse-bias band diagram shows the energy bands bending downward. This change reflects the higher barrier potential. The current falls to a small reverse saturation current. It stays close to that saturation value and has the opposite sign, because only a minor carrier flow remains from thermal generation within the depletion region.

P-N Junction Diode Under Bias

energy bands in solids

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Valence and conduction bands explain how electrons behave in solids. In isolated atoms, electrons occupy discrete energy levels that the Bohr model describes well. The hydrogen atom, for example, has specific electron energies labeled by the quantum number n, and higher n values give levels that are less negative and closer together. When atoms move close together in a solid, those discrete levels start to split. This happens because electron orbitals from neighboring atoms overlap. The Pauli...

semiconductors

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Carrier generation and recombination control how free charge carriers change inside a semiconductor. Carrier generation creates electron-hole pairs, or EHPs, when electrons move from the valence band into the conduction band and leave holes behind. Carrier recombination does the opposite and lowers the number of free carriers. In direct-bandgap semiconductors such as gallium arsenide, generation happens efficiently because energy absorption can move a valence electron straight to the...

carrier transport

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p-n junction

P-N Junction Depletion Region

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

P-N junction diodes change behavior under equilibrium, forward bias, and reverse bias. In equilibrium, no external voltage is applied across the junction. Carriers diffuse at the boundary and leave behind charged dopants. Acceptors remain on the p-side, and donors remain on the n-side. These fixed charges form a depletion region and an electric field that blocks further diffusion. The band diagram at equilibrium shows the Fermi levels on both sides aligned. That alignment means the junction is...

metal-semiconductor junctions

Schottky and Ohmic Metal Contacts

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biasing of metal-semiconductor junctions

How Bias Changes Metal-Semiconductor Current

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fermi level

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key terms and concepts

Explore equilibrium, forward bias, and reverse bias in a p-n junction diode, including depletion region changes, band diagrams, and current flow.

P-N Junction Diode Under Bias | 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

P-N Junction Diode Under Bias

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