Name: drift and diffusion in semiconductors
Uploaded: 2024-07-08T13:20:08.000Z
Duration: 1 min 21 s
Channel: JoVE

El transporte de portadores en semiconductores genera corriente, a través de mecanismos de deriva y difusión.
La corriente de deriva surge cuando un campo eléctrico externo hace que las partículas cargadas se aceleren entre colisiones.
Teniendo en cuenta los electrones, la velocidad adicional añadida al movimiento térmico de los electrones se denomina velocidad de deriva. Se puede obtener igualando el impulso perdido durante las colisiones y el impulso obtenido del campo aplicado.
El factor de proporcionalidad -movilidad- caracteriza el transporte de electrones y huecos debido a la deriva.
Las densidades de corriente de deriva para ambos portadores se pueden expresar como el producto de la densidad de carga, la movilidad y la intensidad del campo eléctrico. La suma de estos dos da la densidad total de corriente de deriva. Aquí, el término entre paréntesis da conductividad.
La corriente de difusión es el resultado del movimiento térmico aleatorio de los portadores de regiones de alta a baja densidad de portadores.
La densidad de la corriente de difusión es igual al producto del flujo portador y la constante de proporcionalidad, que incluye la carga elemental y el coeficiente de difusión. Su relación con la movilidad da la relación de Einstein.
Si tanto el campo eléctrico como el gradiente de concentración están presentes, tanto la corriente de deriva como la de difusión contribuyen a la corriente total.

conceptos básicos de semiconductores

La generación de corriente eléctrica en semiconductores está impulsada fundamentalmente por dos mecanismos: deriva y difusión. Estos procesos son esenciales para la funcionalidad y el rendimiento de los dispositivos basados ​​en semiconductores.
Corriente de deriva:
La deriva de los portadores de carga se inicia mediante un campo eléctrico externo (E). Las partículas cargadas, como los electrones y los huecos, experimentan una aceleración entre colisiones con los átomos de la red. Para los electrones, esto da como resultado una velocidad de deriva (v_d) dada por:
<img alt="Equation 1" src="/files/ftp_upload/15155/15155_Equation_1.svg" style="height: 16px;">
Donde μ_e es la movilidad de los electrones y E es la intensidad del campo eléctrico.
La densidad de corriente (J) debida a la deriva de electrones (J_n) y huecos (J_p) se puede expresar como:
<img alt="Equation 2" src="/files/ftp_upload/15155/15155_Equation_2.svg" style="height: 20px;">
Donde q es la carga elemental, n y p, son las concentraciones de electrones y huecos, respectivamente, y μ_n y μ_p son las movilidades de electrones y huecos. La densidad de corriente de deriva total (J_total) es la suma de las densidades de corriente de electrones y huecos:
<img alt="Equation 3" src="/files/ftp_upload/15155/15155_Equation_3.svg" style="height: 20px;">
La conductancia (σ) es entonces la suma de los productos de densidad de carga y movilidad para cada tipo de portador:
<img alt="Equation 4" src="/files/ftp_upload/15155/15155_Equation_4.svg" style="height: 20px;">
Corriente de difusión:
 La difusión se produce debido al movimiento térmico de los portadores, moviéndose desde regiones de mayor concentración a regiones de menor concentración. La densidad de corriente (J_difusión) es:
<img alt="Equation 5" src="/files/ftp_upload/15155/15155_Equation_5.svg" style="height: 36px;">
D_n y D_p son los coeficientes de difusión de electrones y huecos, respectivamente, y dn/dx y dp/dx son los gradientes de concentración de electrones y huecos.
Las relaciones de Einstein vinculan la movilidad y el coeficiente de difusión tanto para los electrones como para los huecos:
<img alt="Equation 6" src="/files/ftp_upload/15155/15155_Equation_6.svg" style="height: 36px;">
 Donde k es la constante de Boltzmann y T es la temperatura absoluta.
Cuando están presentes tanto un campo eléctrico como un gradiente de concentración, la densidad de corriente total es la suma de los componentes de deriva y difusión. En aplicaciones del mundo real, estos fenómenos se analizan utilizando las ecuaciones de semiconductores, un conjunto de ecuaciones diferenciales que describen el comportamiento de los portadores de carga en un semiconductor.

Conceptos básicos de semiconductores

El transporte de portadores en semiconductores genera corriente, a través de mecanismos de deriva y difusión.
La corriente de deriva surge cuando un campo eléctrico externo ...

Education

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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

Carrier Transport

drift and diffusion in semiconductors

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 strength.

The current density from drift can be written for electrons and for holes. It depends on the elementary charge, the concentrations of electrons and holes, and their mobilities. The total drift current density is the sum of the electron and hole parts. Conductance is then related to the charge density and mobility of each carrier.

Diffusion current comes from thermal motion. Carriers move from regions with higher concentration to regions with lower concentration. For electrons and holes, diffusion current density depends on the diffusion coefficients and the concentration gradients.

Mobility and diffusion are linked by the Einstein relations. These relations connect the electron and hole mobility terms with their diffusion coefficients, along with temperature, the Boltzmann constant, and absolute temperature. When both an electric field and a concentration gradient are present, the total current density is the sum of drift and diffusion. In real semiconductor analysis, these effects are described with semiconductor equations, which are differential equations for charge-carrier behavior.

Drift and Diffusion in Semiconductors

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Explore how electrons and holes create current in semiconductors through drift and diffusion, and see how mobility, concentration, and temperature shape carrier motion.

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electrical engineering

Drift and Diffusion in Semiconductors

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