Name: semiconductor charge carriers: creation and loss
Uploaded: 2024-07-08T13:20:08.000Z
Duration: 1 min 22 s
Channel: JoVE

La generación de portadores se refiere a la creación de pares electrón-hueco.
La generación de banda a banda se produce en semiconductores de banda prohibida directa a través de la excitación térmica o la absorción de fotones. En dichos semiconductores, el máximo de la banda de valencia y el mínimo de la banda de conducción tienen el mismo momento.
La generación indirecta de portadores se produce mediante la absorción de energía reticular de los fonones y es dominante en los semiconductores de banda prohibida indirecta, que tienen su banda de valencia máxima y su banda de conducción mínima en diferentes momentos.
En la generación de Auger, los portadores se generan consumiendo la energía de una partícula altamente energética. Estas mismas partículas de alta energía pueden generar múltiples pares electrón-hueco utilizando el alto campo eléctrico disponible durante la ionización por impacto.
Por el contrario, la recombinación es el proceso de aniquilación de electrones y huecos.
En la recombinación de banda a banda, el electrón pasa de la banda de conducción a la banda de valencia, liberando un fotón.
Durante la recombinación indirecta, se utilizan estados de energía localizados llamados trampas para las transiciones entre las bandas de conducción y valencia, liberando energía en forma de calor.
La recombinación de barrena implica la recombinación de un electrón y un hueco, transfiriendo la energía resultante a otro portador.

conceptos básicos de semiconductores

Carrier Generation and Recombination

La generación de portadores es el proceso mediante el cual se crean pares electrón-hueco (EHP) dentro del semiconductor. En los semiconductores de banda prohibida directa, como el arseniuro de galio (GaAs), esto ocurre de manera eficiente cuando la absorción de energía hace que los electrones de valencia salten a la banda de conducción, dejando agujeros.
Este proceso está dado por la tasa de generación G y es eficiente debido a la conservación del momento entre el máximo de la banda de valencia y el mínimo de la banda de conducción.
La generación indirecta implica un paso intermedio y es típica de los semiconductores de banda prohibida indirecta como el silicio (Si). Los semiconductores de banda prohibida indirecta requieren un impulso adicional de los fonones, lo que hace que la generación de portadoras sea menos eficiente. La generación de barrena y la ionización por impacto producen múltiples EHP en entornos de alta energía, como campos eléctricos intensos.
La recombinación es el proceso que reduce el número de transportistas gratuitos. La recombinación directa de banda a banda ocurre en semiconductores como el arseniuro de galio, donde los electrones y los huecos se recombinan directamente sin estados intermedios.
La tasa de recombinación para un semiconductor tipo n, donde los electrones son los portadores mayoritarios, viene dada por:
<img alt="Equation 1" src="/files/ftp_upload/15154/15154_Equation_1.svg" style="height: 20px;">

Donde B es el coeficiente de recombinación, y “n” y “p”, son las concentraciones de electrones y huecos, respectivamente. La recombinación indirecta implica trampas: estados de energía localizados dentro de la banda prohibida. Los portadores son capturados temporalmente por estos estados y luego se recombinan, liberando energía en forma de calor, un proceso no radiativo.
El equilibrio entre generación y recombinación se describe por:
<img alt="Equation 2" src="/files/ftp_upload/15154/15154_Equation_2.svg" style="height: 20px;">
En condiciones de no equilibrio, el exceso de portadores provoca una tasa de recombinación neta U, que tiende a restablecer el equilibrio. En inyección de bajo nivel, donde la concentración de portador minoritario (Δp) es significativamente menor que la concentración de portador mayoritario, la tasa es:
<img alt="Equation 3" src="/files/ftp_upload/15154/15154_Equation_3.svg" style="height: 18px;">
Las tasas de generación de portadores y recombinación están equilibradas en el equilibrio térmico. Sin embargo, cuando fuerzas externas como la luz o los campos eléctricos perturban este equilibrio, el semiconductor entra en un estado de no equilibrio. La dinámica de retorno al equilibrio implica interacciones complejas entre estos mecanismos de generación y recombinación.

Conceptos básicos de semiconductores

La generación de portadores se refiere a la creación de pares electrón-hueco.
La generación de banda a banda se produce en semiconductores de banda prohibida directa ...

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

semiconductor charge carriers: creation and loss

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 conduction band. This works well when momentum is conserved between the valence band maximum and the conduction band minimum. Indirect generation is different and is common in indirect-bandgap semiconductors like silicon. It uses an intermediate step and needs extra momentum from phonons, so it is less efficient.

Some high-energy conditions can create more than one EHP. Auger generation and impact ionization both produce multiple electron-hole pairs, especially in strong electric fields. These processes show how carrier populations can rise quickly under extreme energy input.

Recombination removes free charge carriers. In direct band-to-band recombination, seen in materials like gallium arsenide, electrons and holes recombine directly without a middle state. For an n-type semiconductor, where electrons are the majority carriers, the recombination rate depends on the recombination coefficient B and on the electron and hole concentrations, n and p.

Indirect recombination uses traps, which are localized energy states inside the bandgap. Carriers can be captured by these states and then recombine later. This process releases energy as heat, so it is non-radiative.

At thermal equilibrium, generation and recombination are balanced. When light or an electric field pushes the semiconductor out of equilibrium, excess carriers create a net recombination rate U that works to restore balance. At low-level injection, where the minority carrier change Δp is much smaller than the majority carrier concentration, the recombination rate follows a simpler form. These interactions describe how semiconductors return to equilibrium after disturbance.

Semiconductor Charge Carriers: Creation and Loss

semiconductor-charge-carriers-creation-and-loss

energy bands in solids

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carrier generation and recombination

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...

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P-N Junction Diode Under Bias

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fermi level

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key terms and concepts

Learn how semiconductors create electron-hole pairs, lose carriers through recombination, and return to equilibrium after light or electric field changes.

Semiconductor Charge Carriers: Creation and Loss | 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

Semiconductor Charge Carriers: Creation and Loss

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