Name: how bias changes metal-semiconductor current
Uploaded: 2024-07-08T13:20:09.000Z
Duration: 1 min 27 s
Channel: JoVE

금속 및 n형 반도체 접합을 바이어싱하는 것은 반도체를 접지하는 동안 금속에 전압을 인가하는 것을 포함합니다. 결과 전류는 금속에서 반도체로 흐를 때 양수입니다.
쇼트키 접합의 경우 양의 전압을 가하면 금속의 페르미 수준이 낮아져 반도체의 전자 장벽이 감소하고 반도체에서 금속으로의 순 전자 흐름이 가능해집니다. 이로 인해 순방향 바이어스 전류가 빠르게 증가합니다.
반대로, 음의 전압은 금속의 페르미 수치를 상승시켜 반도체에서 금속으로의 전자 흐름을 차단합니다. 그러나 일부 전자는 접합 장벽을 극복하여 작은 역 바이어스 전류를 유발합니다.
옴 접합의 경우, 작은 양의 전압조차도 장벽이 없기 때문에 큰 순방향 바이어스 전류를 트리거합니다. 역 바이어싱에서는 금속에서 반도체로의 전자 흐름에 대한 작은 장벽이 존재하며, 역 바이어스가 10분의 1볼트를 초과하면 사라집니다.
이 동작은 금속 및 p형 반도체로 형성된 접촉에 대해 반전됩니다.
금속-반도체 접합을 바이어싱하면 전류 흐름을 제어할 수 있으며, 이는 다이오드, 트랜지스터 및 광전지와 같은 장치에 필수적입니다.

금속-반도체 접합의 바이어싱

바이어싱 금속-반도체 접합에는 접합에 전압을 가하는 작업이 포함됩니다. 구체적으로, 금속은 전압원에 연결되고 반도체는 접지됩니다. 이 기술은 다이오드, 트랜지스터, 광전지 등 전자 장치에서 전류 흐름의 방향과 크기를 제어하는 ​​데 필수적입니다.
반도체가 n형인 쇼트키 접합에서 반도체를 기준으로 금속에 양의 전압을 가하면 페르미 레벨이 감소합니다. 이는 반도체의 전자가 금속으로 이동하기 위해 극복해야 하는 에너지 장벽을 낮춥니다. 이를 통해 반도체에서 금속으로 전자의 상당한 흐름이 가능해지며 접합이 순방향 바이어스될 때 전류가 급격히 증가합니다. 음의 전압이 가해지면 상황은 반전됩니다. 금속의 페르미 준위가 상승하여 반도체에서 금속으로의 전자 흐름에 대한 장벽이 강화됩니다. 그럼에도 불구하고 소수의 전자가 장벽을 극복하여 약간의 역바이어스 전류를 생성할 수 있습니다.
옴 접합은 다르게 동작합니다. 중요한 장벽이 없기 때문에 약간의 양의 전압이라도 큰 순방향 바이어스 전류를 유도하여 반도체에서 금속으로 전자가 쉽게 흐르게 할 수 있습니다. 역바이어스에서는 금속에서 반도체로의 전자 흐름에 대한 최소한의 장벽이 존재하지만 역바이어스 전압이 수십 볼트를 초과하면 이 장벽은 효과적으로 사라집니다.
p형 반도체의 상호작용 역학은 변화합니다. 쇼트키 접합과 옴 접합 모두에서 n형 반도체에 대해 설명된 동작이 반대입니다. 바이어스를 통해 전류 흐름을 조작하는 능력은 많은 전자 부품의 작동에 필수적이며 광범위한 장치의 기능에 대한 기반을 제공합니다.

금속 및 n형 반도체 접합을 바이어싱하는 것은 반도체를 접지하는 동안 금속에 전압을 인가하는 것을 포함합니다. 결과 전류는 양수입니다 ...

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 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 reduces the barrier electrons in the semiconductor must cross to move into the metal. As a result, many electrons flow from the semiconductor to the metal, and the current rises quickly in forward bias.

A negative voltage reverses this effect. The metal Fermi level rises, which increases the barrier for electrons moving from the semiconductor to the metal. A small reverse current can still appear because a few electrons are able to cross the barrier.

Ohmic junctions behave differently because they do not have a large barrier. Even a small positive voltage can produce a large forward current, so electrons move easily from the semiconductor to the metal. In reverse bias, there is only a small barrier for electrons moving from the metal to the semiconductor, and that barrier can disappear if the reverse voltage goes beyond a few tenths of a volt.

The behavior changes again with p-type semiconductors. In both Schottky and Ohmic junctions, the n-type behavior is reversed. This control over current flow is important for many electronic components and supports the function of a wide range of devices.

How Bias Changes Metal-Semiconductor Current

how-bias-changes-metal-semiconductor-current

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 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

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

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

Learn how biasing changes current in Schottky and Ohmic metal-semiconductor junctions, including n-type and p-type behavior in electronics.

How Bias Changes Metal-Semiconductor Current | 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

How Bias Changes Metal-Semiconductor Current

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