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

캐리어 생성은 전자-정공 쌍의 생성을 나타냅니다.
Band-to-band 생성은 열 여기 또는 광자 흡수를 통해 직접 밴드 갭 반도체에서 발생합니다. 이러한 반도체에서 원자가 대역 최대값과 전도 대역 최소값은 동일한 운동량을 갖습니다.
캐리어의 간접 생성은 포논에서 격자 에너지를 흡수하여 발생하며 서로 다른 모멘트에서 원자가 대역 최대와 전도 대역 최소값을 갖는 간접 밴드갭 반도체에서 지배적입니다.
오거 생성에서 캐리어는 고에너지 입자의 에너지를 소비하여 생성됩니다. 이러한 동일한 고에너지 입자는 충격 이온화 중에 사용 가능한 높은 전기장을 사용하여 여러 전자-정공 쌍을 생성할 수 있습니다.
대조적으로, 재결합은 전자와 정공을 소멸시키는 과정입니다.
Band-to-band 재결합에서 전자는 전도에서 원자가 대역으로 전이하여 광자를 방출합니다.
간접 재결합 동안, 트랩(trap)이라고 하는 국부적인 에너지 상태는 전도대와 원자가 대역 사이의 전환에 사용되어 에너지를 열로 방출합니다.
오거 재결합은 전자와 정공의 재결합을 포함하여 결과 에너지를 다른 운반체로 전달합니다.

반도체의 기초

Carrier Generation and Recombination

캐리어 생성은 반도체 내에서 전자-정공 쌍(EHP)이 생성되는 과정입니다. 갈륨비소(GaAs)와 같은 직접 띠틈 반도체에서 이는 에너지 흡수로 인해 원자가 전자가 전도대로 도약하여 정공을 남길 때 효율적으로 발생합니다.

이 과정은 생성율 G로 주어지며 가전자대 최대값과 전도대 최소값 사이의 운동량 보존으로 인해 효율적입니다.

간접 생성은 중간 단계를 포함하며 실리콘(Si)과 같은 간접 밴드갭 반도체에서 일반적입니다. 간접 띠틈 반도체는 포논으로부터 추가적인 추진력을 필요로 하므로 캐리어 생성의 효율성이 떨어집니다. 오거 생성 및 충격 이온화는 강한 전기장과 같은 고에너지 환경에서 여러 EHP를 생성합니다.

재결합은 자유 전하 캐리어의 수를 줄이는 과정입니다. 직접 밴드 간 재결합은 갈륨비소와 같은 반도체에서 발생하며, 여기서 전자와 정공은 중간 상태 없이 직접 재결합됩니다.

전자가 다수 캐리어인 n형 반도체의 재결합 속도는 다음과 같이 계산됩니다.
<img alt="Equation 1" src="/files/ftp_upload/15154/15154_Equation_1.svg" style="height: 20px;">

여기서 B는 재결합 계수이고, n과 p는 각각 전자와 정공의 농도입니다. 간접 재결합에는 트랩, 즉 밴드갭 내의 국부적인 에너지 상태가 포함됩니다. 캐리어는 이러한 상태에 의해 일시적으로 포획된 다음 재결합하여 비방사 과정인 열로 에너지를 방출합니다.

생성과 재조합 사이의 평형은 다음과 같이 설명됩니다.

<img alt="Equation 2" src="/files/ftp_upload/15154/15154_Equation_2.svg" style="height: 20px;">

비평형 조건에서 과잉 캐리어는 순 재결합 속도 U를 유발하여 평형을 회복하는 경향이 있습니다. 소수 캐리어 농도(Δp)가 다수 캐리어 농도보다 상당히 낮은 저준위 주입에서 속도는 다음과 같습니다.

<img alt="Equation 3" src="/files/ftp_upload/15154/15154_Equation_3.svg" style="height: 18px;">

캐리어 생성 및 재결합 속도는 열 평형에서 균형을 이룹니다. 그러나 빛이나 전기장 같은 외부 힘이 이 평형을 방해하면 반도체는 비평형 상태에 들어갑니다. 평형으로 돌아가는 역학에는 이러한 생성 과정과 재조합 과정 간의 복잡한 상호 작용이 포함됩니다.

캐리어 생성은 전자-정공 쌍의 생성을 나타냅니다.
Band-to-band 생성은 열 여기를 통해 직접 밴드 갭 반도체에서 발생합니다 ...

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

Basics of Semiconductors

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

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...

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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...

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 Diode Under Bias

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Schottky and Ohmic Metal Contacts

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How Bias Changes Metal-Semiconductor Current

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fermi level

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Vacuum Level and Schottky Barriers

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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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