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

LED 내의 p-n 접합은 빛을 생성하기 위해 외부 바이어싱이 필요합니다.
순방향 바이어싱은 배터리의 양극 단자가 p측에 연결되고 음극 단자가 n측에 연결된 pn 접합에 전압을 적용하는 것을 포함합니다. 인가된 전압은 접합 전위에 반대하여 장벽 폭을 줄입니다.
이렇게 감소된 장벽 폭은 대다수 캐리어 확산을 증가시켜 전류 흐름을 가능하게 합니다. 확산 전류는 드리프트 전류보다 높고 순 전류는 p에서 n으로 순방향으로 흐릅니다.
확산 중에 접합 영역의 전자와 정공의 재결합은 광자를 방출하여 LED를 빛나게 합니다.
역 바이어스에서 배터리의 양극 단자는 n측에 연결되고 음극은 p측에 연결됩니다.
이렇게 하면 적용된 전위가 접합 전위에 추가됨에 따라 LED가 발광하는 것을 방지하여 장벽 폭이 증가하고 다수 캐리어 확산이 감소합니다.
순 전류는 소수 캐리어로 인해 얻어지는 작은 드리프트 전류입니다.
역 바이어스 전압이 특정 임계값을 초과하면 접합 파괴가 발생하여 큰 전류 흐름이 발생합니다.

p-n 접합의 바이어싱

p-n 접합 다이오드의 작동에는 순방향 바이어스, 역방향 바이어스 및 평형을 비롯한 다양한 바이어스 조건이 포함됩니다.
평형 상태에서는 p-n 접합에 외부 전압이 가해지지 않습니다. 공핍 영역은 캐리어의 확산으로 인해 접합 계면에 형성되며, 이로 인해 하전된 도펀트, p측의 억셉터, n측의 도너가 남게 됩니다. 이러한 움직이지 않는 전하는 캐리어의 추가 확산을 방지하는 전기장을 생성합니다. 관련된 에너지 밴드 다이어그램은 양쪽의 페르미 준위가 정렬되어 평형을 나타냄을 보여줍니다. 접합을 가로지르는 내장된 전위는 접합을 가로지르는 캐리어의 순 흐름을 방지합니다.
다이오드가 순방향 바이어스되면 인가된 전압은 장벽 전위를 감소시키고 공핍 영역의 폭을 좁힙니다. 결과적으로 캐리어는 쉽게 접합을 통과할 수 있으며 해당 밴드 다이어그램은 에너지 밴드가 위쪽으로 구부러져 장벽 전위가 감소함을 나타냅니다. 순방향 바이어스 하에서 다이오드 양단의 전류는 인가된 전압에 따라 기하급수적으로 증가합니다.
역 바이어스에서는 외부 전압이 반대 방향으로 인가되어 공핍 영역이 넓어지고 장벽 전위가 증가하여 캐리어가 접합을 통과하기 어렵게 되어 전류 흐름이 매우 작은 역포화 전류로 감소됩니다. 역방향 바이어스에 대한 에너지 밴드 다이어그램은 밴드가 아래쪽으로 구부러져 장벽 전위가 증가했음을 나타냅니다. 역방향 바이어스의 전류는 작은 상수 값입니다. 이는 포화 전류에 가깝지만 반대 부호를 가지며, 고갈 영역 내의 열 생성으로 인한 캐리어의 작은 흐름을 반영합니다.

P-N 접합의 바이어싱

LED 내의 p-n 접합은 빛을 생성하기 위해 외부 바이어싱이 필요합니다.
순방향 바이어싱은 pn 접합에 전압을 적용하는 것을 포함합니다.

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

Basics of Semiconductors

반도체의 기초

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

Valence and Conduction Bands in Silicon

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

Energy Bands in Metals and Insulators

Materials conduct electricity in different ways because their energy bands are arranged differently. Metals, semiconductors, and insulators can be compared with energy band diagrams. These diagrams show how easily electrons can move when an electric field is applied. Metals such as copper, zinc, and lead have low resistivity. Their conduction band is not fully occupied, or it overlaps with the valence band, so a band gap is essentially absent. Electrons in the highest valence energy levels can...

types of semiconductors

Intrinsic and Doped Semiconductors

Intrinsic semiconductors are very pure materials with no impurities. At absolute zero, they act as perfect insulators because the valence electrons are bound and the conduction band is empty. That means electrical conduction cannot occur under those conditions. The Fermi level helps describe the chance that an energy level is occupied by an electron at thermal equilibrium. In an intrinsic semiconductor, the Fermi level sits near the middle of the band gap at absolute zero. As temperature...

carrier generation and recombination

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...

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...

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

Metal contacts with semiconductors can form either Schottky or Ohmic junctions. The result depends on the work function of the metal, the work function of the semiconductor, and how electrons move when the two materials touch. At equilibrium, the Fermi levels align, so charge shifts until both sides match in energy. Schottky barriers form when a metal with work function Φm contacts a semiconductor with a different work function Φs. If Φm is greater than Φs, the semiconductor Fermi level starts...

biasing of metal-semiconductor junctions

How Bias Changes Metal-Semiconductor Current

Biasing metal-semiconductor junctions means applying a voltage across the junction. The metal connects to the voltage source, and the semiconductor is grounded. This setup helps control the direction and size of current in devices such as diodes, transistors, and photovoltaic cells. In a Schottky junction with an n-type semiconductor, a positive voltage on the metal lowers its Fermi level. A Fermi level is the energy level that helps describe how electrons are distributed. Lowering this level...

fermi level

Fermi Level in Semiconductors

The Fermi level is a key energy level in semiconductors. It sits between the lower-energy valence band and the higher-energy conduction band. The Fermi-Dirac function, which follows an S-shaped curve, shows the chance that an energy state is filled by an electron at a given temperature. At absolute zero, electrons occupy every energy state up to the Fermi level. States above it stay empty. As temperature rises, electrons gain energy and can move into vacant states above the Fermi level. In an...

fermi level dynamics

Vacuum Level and Schottky Barriers

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

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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