Drift Current And Diffusion Current In Semiconductors Pdf


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16.04.2021 at 07:21
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drift current and diffusion current in semiconductors pdf

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P-N Junction Diodes

Any motion of free carriers in a semiconductor leads to a current. This motion can be caused by an electric field due to an externally applied voltage, since the carriers are charged particles. We will refer to this transport mechanism as carrier drift. In addition, carriers also move from regions where the carrier density is high to regions where the carrier density is low. This carrier transport mechanism is due to the thermal energy and the associated random motion of the carriers.

Drift and diffusion are responsible for generating current in semiconductors and the overall current density is the sum of the drift and diffusion currents. Drift current arises from the movement of carriers in response to an applied electric field. Positive carriers holes move in the same direction as the electric field while negative carriers electrons move in the opposite direction. The net motion of charged particles generates a drift current that is in the same direction as the applied electric field. The movement of charge carriers from higher concentration to lower concentration generates diffusion current. This occurs when a semiconductor is doped non-uniformly then there is a non-uniform distribution of carriers or a concentration gradient.

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Carrier Transport Study Notes for Electronics and communication Engineering

P-n junction diodes form the basis not only of solar cells, but of many other electronic devices such as LEDs, lasers, photodiodes and bipolar junction transistors BJTs. A p-n junction aggregates the recombination, generation, diffusion and drift effects described in the previous pages into a single device. A p-n junction with no external inputs represents an equilibrium between carrier generation, recombination, diffusion and drift in the presence of the electric field in the depletion region. Despite the presence of the electric field, which creates an impediment to the diffusion of carriers across the electric field, some carriers still cross the junction by diffusion. In the animation below, most majority carriers which enter the depletion region move back towards the region from which they originated. However, statistically some carriers will have a high velocity and travel in a sufficient net direction such that they cross the junction.

In a semiconductor , the majority and minority charge carriers will exit in p-type or n-type. Because both the types of semiconductors will present over a single crystal at the center so that PN-junction can be formed. When the doping of this junction diode is done non-uniformly then charge carriers movement will be an exit from high to low concentration which leads to the recombination of carriers as well as to the diffusion process. There is an additional method is also occurs based on the applied electric field namely drift current. This article discusses the main differences between drift current and diffusion current. In a semiconductor material, the drift , as well as diffusion currents, will occur. Semiconductors are fabricated with two kinds of materials namely p-type as well as n-type.


•Diffusion: Particles tend to spread out or redistribute from areas Given current density J (I=J x Area) flowing in a semiconductor block with face area A under.


What are Drift Current and Diffusion Current : Their Differences

In a semiconductor either it may be p-type or n-type there exists some of the majority and the minority charge carriers. As the p-type and n-type present on a single crystal at the center, there is the formation of the p-n junction. The basic device formed because of the above process is the p-n junction diode. We cover the basic differences between Drift Current and Diffusion Current below with a comparison table.

This is the current which is due to the transport of charges occurring because of non-uniform concentration of charged particles in a semiconductor. The drift current, by contrast, is due to the motion of charge carriers due to the force exerted on them by an electric field. Diffusion current can be in the same or opposite direction of a drift current.

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2 Comments

Jolie L.
22.04.2021 at 14:03 - Reply

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Alaor M.
24.04.2021 at 08:56 - Reply

There are two types of current through a semiconducting material – one is drift current and the other is diffusion current. Similar is the case in semiconductor. However, the movement of the charge carriers may be erratic path due to collisions with other atoms, ions and carriers.

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