Pn junction diode and characteristics of pn junction diode. Volume ii 2nd edition modular series on solid state dev. The valence band and conduction band in ntype material are slightly lower than that of ptype material. Pn junction article about pn junction by the free dictionary. Since a junction forms between a p type and n type material it is called as pn junction. Pdf we have developed an analytic model for the radial pnjunction in a nanowire nw coreshell structure utilizing as a new building block in. However, if we join or fuse these two semiconductor materials together they behave in a very different way merging together and producing what is generally. You can visualize a junction by taking a look at the adjacent diagram which is a very simple sketch showing such a junction.
Most semiconductor devices contains one or more pn junctions. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. The diode is firmed by doping a semiconductor like silicon or germanium with trivalent impurity e. And based on the applied voltage, there are three possible biasing conditions for the pn junction diode, which are as follows. The equation describing the distribution of the diffused profile of impurities in fig. The increase in resistance of the pn junction results in the junction behaving as an insulator. Chapter 4 pn junctions pn junction is present in perhaps every semiconductor device. Pn homojunction non linear device rectifier devices composants redresseur 2 devices reach the same results. The p positive side contains an excess of holes, while the n negative side contains an excess of electrons in. They are also called pn diodes in analogy with vacuum diodes. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Pn junction in equilibrium pn junctions are important for the following reasons. Lecture 5lecture 5 pn junction diodes quantitative analysis.
Well as a 3rd year physics student i did a report on semiconductors. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Physics of semiconductor devices pn junction depletion width. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode. 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. When the ntype semiconductor and ptype semiconductor materials are first joined together a very large density gradient exists between both sides of the pn junction. The recombination at the junction allows battery current to flow through the pn junction diode. Supposing that the junction is reverse biased, and that the semiconductor material is homogenous e. Lecture 5lecture 5 pn junction diodes quantitative analysis math, math and more math georgia tech ece 4833 dr. Semiconductor device characteristics and operation are intimately connected to these pn junctions, therefore considerable attention is devoted initially to this basic device. A pn junction with open terminals excluding minority carriers f. The term junction implies the boundary or region of transition between n type and p type semiconductor material.
The plane which divides these two parts is obviously known as the junction since these both types meet at this plane. Forming a pn junction once in the ptype they can drop down into the valence band and to fill up one of the hole states. Pdf theory of nanowire radial pnjunction, researchgate. Chapter 4 pn junctions university of california, berkeley. Zero bias no external voltage potential is applied to the pn junction diode.
The pindiode is an alteration of the pn junction for particular applications. In addition, pn junction is a vehicle for studying the theory. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. Draw the energy level diagram of a pn junction and explain how a junction barrier is developed across an unbiased junction. The word diode can be explained as di means two and ode is obtained from electrode. Jan 21, 2019 what is a pn junction when a ptype semiconductor is suitably joined to an ntype semiconductor, the contact surface is called pn junction.
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. The theory of pn junctions in semiconductors and pn junction transistors. This chapter introduces several devices that are formed by joining two different. A pn junction is an interface or a boundary between two semiconductor material types, namely the ptype and the ntype, inside a semiconductor. Also, it explains the phenomenon of shockleyqueisser limit. The pn junction is the basic structure of solar cell, lightemitting diode, and diode laser, and is present in all types of transistors.
A pn junction consists of two semiconductor regions with opposite doping type as. Fmpside f m nside 0 0 d a m n p qn qn f x x maximum field in the pn junction from2 1 0 1 2 051015xp xn s df dx. The shift of electrons from n side of the pn junction to holes annihilated on the p side of the pn junction produces a potential barrier voltage. Pn junction diode baising and its vi characteristics. May 15, 2018 p n junction theory behind p n junction may 15, 2018 february 24, 2012 by electrical4u we can create a pn junction by connecting face to face one ptype sand one ntype semiconductor crystal block by special techniques. On the contrary, even after being a very simple device, it can be used for a large number of applications in many different ways.
Pn and metalsemiconductor junctions the gmu ece department. The pn junction is the fundamental building block of the electronic age. Theoretical background semiconductor diode theory is at the very. When you take a block of silicon and dope part of it with a trivalent impurity and the other part with a pentavalent impurity, a boundary called the pn junction is formed between the resulting ptype and ntype portions. What is a pn junction when a ptype semiconductor is suitably joined to an ntype semiconductor, the contact surface is called pn junction. The pn junction is the basis for diodes, certain transistors, solar cells, and other devices. A pn junction is a boundary or interface between two types of semiconductor materials, ptype. Formation of pn junction in actual practice, a pn junction will not be formed if a ptype. Vi characteristics of pn junction diode electronics post.
Boron or aluminium from one end to form ptype region and with pentavalent impurity like. Draw the vi characteristics of pn junction diode and explain the operation of diodes as with other semiconductor devices is often described by a special graph called a characteristic curve. Zero bias no external voltage is applied to the pn junction diode. P type and n type semiconductors, takenseparately are of very limited use. Chapter 4 pn junctions a pn junction is present in every semiconductor device. The pn junction diode provides characteristics that.
Jan 21, 2019 vi characteristics of pn junction diode. Bipolar junction transistor 4 theory of operation 2 an amplifier is a device that boosts the power of a signal, whilst keeping its waveform the same transistors are used in amplification circuits in normal use as an amplifier, the pn junction between collector and base is reversed biased the junction between emitter and. Well, a pn junction is the most simplest device you can imagine before you enter into this gigantic field. Avalanche multiplication impact ionization of electronhole pairs tunneling through the junction zener breakdown at high doping concentrations, identical to that of tunneling in a metalsemiconductor junction. There is a builtin voltage at the pn junction interface that prevents penetration of electrons into the pside and holes into the nside. The p positive side contains an excess of holes, while the n negative side contains an excess of electrons in the outer shells of the electrically neutral atoms there. The region on the left is p type with an acceptor density na, while the region on the right is n type with a donor density nd.
A pn junction consists of two semiconductor regions with opposite doping type as shown in figure 4. P n junction theory behind p n junction may 15, 2018 february 24, 2012 by electrical4u we can create a pn junction by connecting face to face one ptype sand one ntype semiconductor crystal block by special techniques. At this coupling point, free electrons ntype and holes ptype cancel each other and form a depletion zone that acts as a nonconductive barrier. Valence band p n forming a pn junction electrons continue to diffuse across the junction. The dopants are assumed to be shallow, so that the electron hole density in the n type p type region is. The area of the ptype near the junction becomes more negative due to. It is the most fundamental device element that forms the basis of many electronic devices such as pn diodes, optoelectronic devices like lightemitting diode and photodetector, field. On the pside of the junction, 0 a m p qn f x on the nside of the junction, 0 d m n qn f x at the junction interface. The energy gap between the valence level and the conduction level is midway between that of insulators and conductors such as metals, and thermal energy causes. Voltampere vi characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. After the pn junction diode was developed in the year 1940s, the diode was first exercised as a highpower rectifier, lowfrequency during the year 1952. Here is some more theory for you to make sense of this which i wrote out of my own understanding. The diffusion forms a dipole charge layer at the pn junction interface.
Jul 06, 2016 when you take a block of silicon and dope part of it with a trivalent impurity and the other part with a pentavalent impurity, a boundary called the pn junction is formed between the resulting ptype and ntype portions. Silicon a single silicon atom consists of fourteen negatively. Junction field effect transistor jfet the single channel junction fieldeffect transistor jfet is probably the simplest transistor available. The pn junction solidstate device theory electronics. This lecture uncovers the basic science of semiconductor devices and solar cells, including pn junction and photovoltaic effects. Najmabadi, ece65, winter 2012 high concentration of h on the p side holes diffuse towards the junction high concentration of e on the n side electrons diffuse towards the junction n side is positively charged because it has lost electrons. Pn junction theory for semiconductor diodes electronicstutorials. Chapter 1 semiconductor pn junction theory and applications.
Theory a semiconductor pn junction diode is a two terminal electronic device that allows current in only one direction. The pn junction is of great importance as it is the main control element for the semiconductor devices. A ptype material consists of silicon atoms and trivalent impurity atoms such as. Pn junction the interface at which ptype silicon and ntype silicon make contact with each other. A voltage results from the electric field formed at the junction. In addition, pn junction is a vehicle for studying the theory figure 41 a pn junction can be fabricated by converting a layer of ptype semiconductor into ntype with donor implantation or diffusion. What are the depletion width in the nregion, the depletion width in the pregion, and the builtin potential at 300k. P n junction theory behind p n junction electrical4u. How a pn junction formed in a diode engineering tutorial. Pn junctions consist of two semiconductor regions of opposite type. It is formed by joining a ptype intrinsic semiconductor doped with a trivalent. Formation of pn junction in actual practice, a pn junction will not be formed if.
Such junctions show a pronounced rectifying behavior. First time calculation of the depletion region width and. A pn junction diode is a twoterminal electronics element, which can be classified as either. A pn junction is a device formed by combining ptype doped with b. Energy band diagram of a pn junction a before and b after merging the ntype and p type regions. Pn junction diode is one of the fundamental elements in electronics. The occurrence of an intrinsic layer can significantly increase the breakdown voltage for the application of high. Electron injection qv qv o qv qv o q vbi vr q vbi q vf q vr qvbivf equilibrium electron concentration on the pside because the junction is in equilibrium. 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. We have two conductive blocks in contact with each other, showing no unique properties.
The line dividing the two regions, where n d n a 0, is the metallurgical junction. The pn junction is a versatile element, which can be used as a. The pn junction most semiconductor devices contain. The holes diffuse into the ntype, combine with the free electrons, and cancel each other out.
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