Name: p-n junction depletion region
Uploaded: 2024-07-08T13:20:08.000Z
Duration: 1 min 11 s
Channel: JoVE

Las farolas solares funcionan de forma independiente sin necesidad de una fuente de alimentación externa, ya que contienen uniones p-n dentro de sus células solares.
Una unión p-n se forma añadiendo impurezas pentavalentes a una fina lámina de silicio de tipo p, convirtiendo parte de ella en silicio de tipo n.
El gradiente de concentración de los portadores de carga en ambos lados de la lámina de silicio conduce a la difusión de huecos desde el lado p al lado n y electrones desde el lado n al lado p, generando una corriente de difusión.
La región cercana al cruce queda desprovista de portadores de carga libre, formando la región de agotamiento. Además, las cargas positivas y negativas ligadas netas permanecen en esta región, creando un campo eléctrico y una diferencia de potencial a través de la unión.
El campo eléctrico desplaza los portadores minoritarios en la unión p-n, generando una corriente de deriva que contrarresta la corriente de difusión.
Este campo eléctrico también se opone a cualquier difusión adicional de los portadores mayoritarios a través de la unión.
En equilibrio, la corriente total a través de la unión es la misma en magnitud en ambas direcciones y se indica mediante la energía constante de Fermi.

conceptos básicos de semiconductores

P-N junction

Una unión p-n se forma cuando se unen materiales semiconductores de tipo p y tipo n. En la interfaz de la unión p-n, los huecos del lado p y los electrones del lado n comienzan a difundirse hacia los lados opuestos debido al gradiente de concentración. Esta difusión de portadores conduce a una región alrededor de la unión donde no hay portadores de carga libres, conocida como región de agotamiento. La densidad de carga dentro de la región de agotamiento para el lado n y el lado p puede describirse mediante las ecuaciones:
<img alt="Equation 1" src="/files/ftp_upload/15156/15156_Equation_1.svg" style="height: 20px;">
Donde q es la carga elemental, N_D y N_A son las concentraciones de dopaje donante y aceptor, respectivamente.
Las cargas fijas en la región de agotamiento crean un campo eléctrico (E), que apunta desde el lado n al lado p, oponiéndose a una mayor difusión de los portadores. Este campo eléctrico da lugar a una diferencia de potencial a través de la unión, conocida como voltaje incorporado (V_0), que se puede calcular mediante:
<img alt="Equation 2" src="/files/ftp_upload/15156/15156_Equation_2v2.svg" style="height: 40px;">
Donde, V_T es el voltaje térmico y n_i es la concentración de portador intrínseco.
Hay dos tipos de corrientes que existen en una unión p-n: corriente de difusión debida a la difusión del portador y corriente de deriva debida al campo eléctrico. En el equilibrio, la magnitud de la corriente de difusión es igual a la magnitud de la corriente de deriva, lo que provoca que no haya flujo neto de corriente a través de la unión. En condiciones de circuito abierto, no hay corriente externa y el voltaje incorporado de la capa de agotamiento equilibra el potencial de contacto en las uniones metal-semiconductor, lo que resulta en un voltaje neto cero en los terminales.
El voltaje de barrera incorporado y el ancho de la región de agotamiento desempeñan papeles críticos en el comportamiento de la unión. El ancho de la región de agotamiento determina la capacitancia de la unión y afecta cómo responderá la unión a los voltajes externos.

Conceptos básicos de semiconductores

Las farolas solares funcionan de forma independiente sin necesidad de una fuente de alimentación externa, ya que contienen uniones p-n dentro de sus células solares.
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Electrical Engineering

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Basics of Semiconductors

Conceptos básicos de los semiconductores

KEY TERMS AND CONCEPTS

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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 charges in this region create an electric field that points from the n-side to the p-side. That field opposes further carrier diffusion and helps set up the junction’s built-in voltage, V0.

The built-in voltage across the junction depends on the thermal voltage, VT, and the intrinsic carrier concentration, ni. A p-n junction also has two kinds of current: diffusion current from carrier movement and drift current from the electric field. At equilibrium, these currents are equal in magnitude, so there is no net current flow across the junction.

Under open-circuit conditions, no external current flows. The built-in voltage in the depletion layer balances the contact potential at the metal-semiconductor junctions, so the terminals show zero net voltage. The barrier voltage and the width of the depletion region are important because they control junction behavior and affect the capacitance and response to external voltages.

P-N Junction Depletion Region

energy bands in solids

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p-n junction

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 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...

metal-semiconductor junctions

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biasing of metal-semiconductor junctions

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fermi level

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Vacuum level and Schottky barriers help explain how electrons move between materials. The vacuum level is the energy needed for an electron to escape a material surface. In a semiconductor, it usually sits above the conduction band and serves as a reference for comparing electron energy. Electron affinity is the energy gap between the conduction band minimum and the vacuum level. It shows how easily a semiconductor can accept extra electrons. The work function is the least energy needed to...

key terms and concepts

Learn how a p-n junction creates a depletion region, built-in voltage, and balance between diffusion and drift currents in semiconductor devices.

P-N Junction Depletion Region | 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 Depletion Region

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