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

Os postes solares funcionam de forma independente, sem a necessidade de uma fonte de alimentação externa, pois contêm junções pn dentro de suas células solares.
Uma junção pn é formada pela adição de impurezas pentavalentes a uma fina folha de silício tipo p, convertendo parte dela em silício tipo n.
O gradiente de concentração dos portadores de carga em ambos os lados da folha de silício leva à difusão de buracos do lado p para o lado n e elétrons do lado n para o lado p, gerando uma corrente de difusão.
A região próxima ao entroncamento torna-se desprovida de portadores de carga livre, formando a região de esgotamento. Além disso, as cargas positivas e negativas líquidas permanecem nesta região, criando um campo elétrico e uma diferença de potencial ao longo da junção.
O campo elétrico deriva os portadores minoritários na junção pn, gerando uma corrente de deriva que neutraliza a corrente de difusão.
Este campo elétrico também se opõe a qualquer difusão adicional de portadores majoritários através da junção.
No equilíbrio, a corrente total através da junção é a mesma em magnitude em ambas as direções e é indicada pela energia constante de Fermi.

 noções básicas de semicondutores

P-N junction

Uma junção p-n é formada quando materiais semicondutores do tipo p e do tipo n são unidos. Na interface da junção pn, buracos do lado p e elétrons do lado n começam a se difundir para os lados opostos devido ao gradiente de concentração. Esta difusão de portadores leva a uma região ao redor da junção onde não há portadores de carga livre, conhecida como região de depleção. A densidade de carga dentro da região de depleção para o lado n e o lado p pode ser descrita pelas equações:
<img alt="Equation 1" src="/files/ftp_upload/15156/15156_Equation_1.svg" style="height: 20px;">
Onde q é a carga elementar, N_D e N_A são as concentrações de dopagem do doador e do aceitador, respectivamente.
As cargas fixas na região de depleção criam um campo elétrico (E), apontando do lado n para o lado p, opondo-se à difusão adicional de portadores. Este campo elétrico dá origem a uma diferença de potencial através da junção, conhecida como tensão incorporada (V_0), que pode ser calculada por:
<img alt="Equation 2" src="/files/ftp_upload/15156/15156_Equation_2v2.svg" style="height: 40px;">
 Onde, V_T é a tensão térmica e ni é a concentração intrínseca da portadora.
Existem dois tipos de correntes em uma junção pn: corrente de difusão devido à difusão do portador e corrente de deriva devido ao campo elétrico. No equilíbrio, a magnitude da corrente de difusão é igual à magnitude da corrente de deriva, levando a nenhum fluxo líquido de corrente através da junção. Sob condições de circuito aberto, não há corrente externa, e a tensão incorporada da camada de depleção equilibra o potencial de contato nas junções metal-semicondutor, resultando em tensão líquida zero nos terminais.
A tensão de barreira incorporada e a largura da região de depleção desempenham papéis críticos no comportamento da junção. A largura da região de depleção determina a capacitância da junção e afeta como a junção responderá às tensões externas.

 Noções básicas de semicondutores

Os postes solares funcionam de forma independente, sem a necessidade de uma fonte de alimentação externa, pois contêm junções pn dentro de suas células solares.
Um...

Education

JoVE Core

Electrical Engineering

Engenharia Elétrica

Unit 1

Unidade 1

Basics of Semiconductors

Fundamentos de Semicondutores

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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

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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...

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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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