Space charge region an overview sciencedirect topics. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Pn junction diode applications pn diode applications. Physics of semiconductor devices pn junction depletion. The pn junction is the fundamental building block of the electronic age. In ideal conditions, this pn junction behaves as a short circuit when it is forward biased, and as an open circuit when it is in the reverse biased. Holes drift into nmaterial and find plenty of electrons there.
From xxnnpn da00 under reverse bias, vbi has to be replaced with vbivr. P type and n type semiconductors, takenseparately are of very limited use. Pn junction underbiasing 14 boltzmann s approximation. Convert a part of the ptype semiconductor into ntype silicon semiconductor by adding a small quantity of pentavalent impurity. In a ptype semiconductor, majority carriers are holes or positive charges. Formation of depletion layer, barrier voltage and biasing. A pn junction diode is formed by placing a pdoped semiconductor next to an ndoped semiconductor. Holes are the majority carriers and electrons are the minority carriers. A pn junction diode is formed by doping one side of a piece of silicon with a ptype dopant boran and the other side with a ntype dopant phosphorus. Thus, the quality of the pn junction determines the properties of jfets. A pn junction diode is a two terminal single crystal semiconductor device whose one side is doped with acceptors and other side by donors. Iv relationship of a diode, indicating rectifying behavior. Pn junction diode and its characteristics in chapter 1 understanding the pn junction, we have seen how a pn junction is formed from a ptype and ntype semiconductor. In diamond, the first ultraviolet light emitting diodes with the vertical pn junction were.
Pn junction diode is one of the fundamental elements in electronics. The boltzmann approximation is to say that the resulting current being small compared with the components of this current, we consider that we are still in quasi equilibrium and therefore that the currents equation is still valid by replacing v bi by v. A schottky diode is the preferred rectifier in low voltage, high current applications. In order to initiate the junction formation, click the formjunction button or mouse drag one object toward the other. If the pn junction is strongly asymmetrical, for example. Pn junction diode is a two terminal device, the characteristics of diode depends on the polarity of the external potential applied to the pn junction diode. In a pn junction with no external voltage, the electric field between acceptor and donor ions is called a. What are the depletion width in the nregion, the depletion width in the pregion, and the builtin potential at 300k. A pn junction is formed by doping a crystal in such a way that the. If ptype semiconductor is joined with ntype semiconductor, a pn junction is formed. A pnjunction diode is formed when a ptype semiconductor is fused to an ntype semiconductor creating a potential barrier voltage across the diode junction the effect described in the previous tutorial is achieved without any external voltage being applied to the actual pn junction resulting in the junction being in a state of equilibrium. The junction of n and p semiconductors is free of charge carriers. The junction can be formed by the implantation or diffusion of dopants in an wafer. You just need to take a battery whose values can be varied from o to v volts, connect its positive terminal to the pside of pn junction diode and then connect the negative terminal of battery to the nside of the pn junction diode.
Formation and properties of junction diode physics youtube. Formation of a pn junction pn junctions are formed by joining n type and p type semiconductor materials, as shown below. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Formation of a pnjunction overview joining ntype material with ptype material causes excess electrons in the ntype material to diffuse to the ptype side and excess holes from the ptype material to diffuse to the ntype side. Silicon a single silicon atom consists of fourteen negatively. Pn junction diode baising and its vi characteristics. At the instant of the pn junction formation, the free electrons near the junction. Pdf barrier potential across semiconductor pn junction and. This is the basic construction of the pn junction diode. Such junctions show a pronounced rectifying behavior.
In actual practice, the pn junction is not formed just by bringing a ptype semiconductor block near to an ntype semiconductor block. Since the n type region has a high electron concentration and the p type a high hole concentration, electrons diffuse from the n type side to the p type side. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. Pn junction diode multiple choice questions answers. The name diode is derived from diode which means a device that has two electrodes. To return the semiconductor to separate pieces, click the separate button or drag one object away from the other. Combining continuity and transport equations of holes yields a secondorder. They are also called pn diodes in analogy with vacuum diodes. Abrupt depletion layer approximation let apply bias and calculate current through the pn junction currents in pn junction. For example, a common type of transistor, the bipolar junction transistor, consists of two pn junctions in series, in the form npn or pnp. Pn junction one of the crucial keys to solid state electronics is the nature of the pn junction. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded.
It is the fundamental building block of semiconductor diodes and transistors and a number of other electronic components. As the pn junction is formed, holes from pregion diffuse across the junction and recombine with the electrons in the nregion near the junction resulting in formation of positive ions in the nregion near the junction. Semiconductor diode pn junction diode if donor impurities are introduced into one side and. In a ptype semiconductor, the number p p of holes is much larger than the number of electrons n p p p n p. No generationrecombination in the depletion layer 6. When a pn junction is formed, some of the free electrons in the nregion diffuse across the junction and combine with holes to form negative ions. A pn junction diode is twoterminal or twoelectrode semiconductor device, which allows the electric current in only one direction while blocks the electric current in opposite or reverse direction. Formation of a pn junction diode and its band diagram. This pn junction separates ntype semiconductor from ptype semiconductor fig. When ptype and ntype materials are placed in contact with each other, the junction behaves very differently than either type of material alone. A pn junction is one formed between two semiconductors with different. Please refer the applet to know the fabrication process of the diode. In this video we are going to learn the following topics.
A pn junction is a device formed by combining ptype doped with b,al and. A pn junction aggregates the recombination, generation, diffusion and drift effects described in the previous pages into a single device. Specifically, current will flow readily in one direction forward biased but not in the other reverse biased, creating the basic diode. This presentation is a very informative piece on pn junction diode an important part of electronics education. Questions you should be able to answer by the end of todays lecture. The vacuum diode is a rectifier in that electrons cannot flow from anode to cathode. If we join a piece of p type material to a pieceof n type material such that the crystalstructure remains continuous at the boundary, a pn junction is formed 2. Definition, symbol, and types of diodes electrical4u. When the diode is forwardbiased, it can be used in led lighting applications.
The region in which the ptype and ntype semiconductors are joined is called pn junction. The pn junction is an essential component for junction field effect transistors jfets as it controls the amount of carriers in the channel. There is a builtin voltage at the pn junction interface that prevents penetration of electrons into the pside and holes into the nside. Physics of semiconductor devices pn junction depletion width problem a silicon pn diode has a doping of n d 81015 1 cm3 and n a 210 16 1 cm3. Diamond lateral pn junction diodes have been fabricated via a selective.
In an ntype semiconductor, the majority carriers are negative charge carriers or electrons. A schottky junction is a special case of a pn junction, where metal serves the role of the ptype semiconductor. When a junction is formed in a silicon wafer by doping, a concentration gradient occurs between ptype and ntype materials. If the diode is forward biased, it allows the electric current flow. The combination of ptype and ntype semiconductors results in a junction. The most common method of making p n junction is called alloying. A pn junction is the basic building block of many semiconductor devices like diodes, transistor etc. A voltage results from the electric field formed at the junction. Forward biasing a pn junction diode is very simple. This pn diode applications are very useful for beginners. Download, diode,circuits,tutorial, pdf,25p,download,free,online,book,chm, pdf. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. The pn junction is an interface between a ptype and an ntype region and is used to construct diodes and transistors.
Pn junction diode and characteristics of pn junction diode. A pnjunction is formed when an ntype material is fused together with a ptype. Schottky diodes, tunneling diodes, pnjunctions are the most common. This page of application notes section covers pn junction diode applications. Pn 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.
We can visualize the formation of a pn junction by considering what happens. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. Pn junction diode and its symbol formation of depletion layer barrier voltage biasing of pn junction diode 1. The physical point at which the ntype and ptype semiconductors merge is referred to as the. We have also learned about diffusion current, depletion region. Pn junctions consist of two semiconductor regions of opposite type. Cbse ncert notes class 12 physics semiconductor electronics. Doping with acceptor creates p type semiconductor while doping with donors produces n type. A pn junction is the simplest form of the semiconductor diode. This is a physics video for grade 1112 students about pn junction diode, its properties, characteristics and uses. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. The diffusion forms a dipole charge layer at the pn junction interface. Actually, p n junction is fabricated by special technique, namely growing, alloying and diffusing methods.