Questions you should be able to answer by the end of todays lecture. Pn junction diode plays a vital role in our electronic fields, because of their unique property current flows in only one direction they are used in many electronic or electrical circuits like rectifiers, switches, clippers, clampers, voltage multipliers in this article, we will learn about what is a pn junction diode and how it works and also effect on pn junction diode with different. A pn junction is one formed between two semiconductors with different. We also explained how depletion region is created, what barrier potential is and what diffusion. When ptype and ntype materials are placed in contact with each other, the junction behaves very differently than either type of material alone. Concentration of holes in ntype material is very low. Request pdf on oct 1, 2019, muhammad zahir iqbal and others published formation of pn junction with chemical modification of graphenehexagonal boron nitride heterostructure find, read and. Pn junction diode and characteristics of pn junction diode. Pn junction diode applications pn diode applications. Here, boron is used which when put in the silicon crystal. The formation of a pn semiconductor junction is described and its conduction properties are discussed. Pn junction diode engi 242 elec 222 pn junction diode diode model analysis ideal approximation exact diode specification sheets diode resistance static resistance rd.
In actual practice, the pn junction is not formed just by bringing a ptype semiconductor block near to an ntype semiconductor block. The animation below shows the formation of the e at the junction. Pn junction theory for semiconductor diodes electronicstutorials. Pdf semiconductor pn junction diodes jeeva bhoopathy. Lots of electrons on the left hand side of the junction want to diffuse to the right and lots of holes on the right hand side of the junction want to move to the left.
Pn junction this chapter schottky barrier or metal sc contact next chapter 2. The junction can be formed by the implantation or diffusion of dopants in an wafer. Since no free charge carriers can rest in a position where there is a potential barrier, the regions on either sides of the junction now become completely depleted of. A silicon pn junction can be realized by the formation of a junction between an ntype and a ptype doped region. Ppt pn junction diode powerpoint presentation free to. The pn junction is the fundamental building block of the electronic age.
Suppose we have a intrinsic semiconductor like silicon. The animation below shows the formation of the e at the junction between n and ptype material. The combination of ptype and ntype semiconductors results in a junction. Thus a reverse biased pn junction does not conduct current. At the instant of the pn junction formation free electrons near the junction diffuse across the junction into the p region and combine with holes. Before explaining the formation of a pn junction, i would like to remind you about the real basic stuff. A pn junction is the basic building block of many semiconductor devices like diodes, transistor etc. This is a physics video for grade 1112 students about pn junction diode, its properties, characteristics and uses.
This pn diode applications are very useful for beginners. A free powerpoint ppt presentation displayed as a flash slide show on id. All books are in clear copy here, and all files are secure so dont worry about it. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Because of its electrical properties, silicon is called a semiconductor. Filling a hole makes a negative ion and leaves behind a positive ion on the n side. Download module 1 semiconductor pn junction diodes book pdf free download link or read online here in pdf. This video is highly rated by class 12 students and has been viewed 1014 times. P n junction formation a the device formed by joining atomically a wafer of ptype semiconductor to the wafer of ntype semiconductor is known as pn junction. Cbse ncert notes class 12 physics semiconductor electronics. Pn junction diode multiple choice questions answers.
This chapter introduces several devices that are formed by joining two different materials together. Convert a part of the ptype semiconductor into ntype silicon semiconductor by adding a small. The free electrons in the n region are randomly drifting in all directions. This presentation is a very informative piece on pn junction diode an important part of electronics education. A pn junction 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 result is that some of the free electrons from the donor impurity atoms begin to migrate across this newly formed junction to fill up the holes in the ptype. The pn junction diode the negative terminal of the biasvoltage source pushes the conductionband electrons in the n region toward the pn junction, while the positive terminal pushes the holes in the p region toward the pn junction when it overcomes the barrier potential v b, the external voltage source provides the n region electrons with enough energy to penetrate the. This pn junction separates ntype semiconductor from ptype semiconductor fig. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction.
Since a lower e c means a higher voltage see section 2. The junction s formation mechanism 3 flat fermi level. In this physics video in hindi we explained the working of a pn junction diode for class 12. Pn junction diode lecture2 outline about pn diode pn junction formation pn junction realization barrier height thermal equilibrium equilibrium depletion approximation abrupt junction pn junction bias. Due to concentration difference holes from pside diffuse to nside leaving behind ve immobile ions and electrons from nside diffuse to pside leavin. Pn junction one of the crucial keys to solid state electronics is the nature of the pn junction. At the instant of the pn junction formation, the free electrons near the junction in the n region begin to diffuse across the junction into the p region where they combine with holes near the junction, as shown in figure b. Pn junctions are formed by joining ntype and ptype semiconductor.
Initiate the pn junction formation by clicking the formjunction button or using mouse drag and watch the physical system approach a new electrothermal equilibrium which is characterized by a constant fermi level throughout the material. If we plot it in the iv plot, the power will be the area of the rectangle formed by the values. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. When the pn junction is formed, the n region loses free electrons as they diffuse across the junction. Classification into metals,semiconductors and insulators. Contains a ptype and an ntype region in a closed boundary. A ptype has a lot of holes and an ntype lot of electrons. Similarly, holes flow by diffusion from the ptype side to the ntype side.
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. Equilibrium band diagrams appear below the semiconductor. The most common method of making p n junction is called alloying. 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. Pn junction and metalsemiconductor junction are analyzed in the forward bias and. Being free particles, electrons start diffusing from ntype material into pmaterial being free particles, holes, too, start diffusing from ptype material into nmaterial have they been neutral particles, eventually all the free. The region in which the ptype and ntype semiconductors are joined is called pn junction. This creates a layer of positive charges near the junction. This page of application notes section covers pn junction diode applications. P type and n type semiconductors, takenseparately are of very limited use. We will see what happens when we have a single crystal with a ptype semiconductor on one side and an ntype on the other. For example a silicon pn junction can be formed by the implantation of boron atoms in an ntype silicon wafer. Being free particles, electrons start diffusing from ntype material into pmaterial being free particles, holes, too, start diffusing from ptype material into nmaterial have they been neutral particles, eventually all the free electrons. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity.
In this video, lets explore the famous pn junction. Apr 22, 2020 p n junction formation class 12 video edurev is made by best teachers of class 12. This region is called the depletion region since the electric field quickly sweeps free carriers out, hence the region is depleted of free carriers. Read online module 1 semiconductor pn junction diodes book pdf free download link book now.
Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Concentration of free electrons in ptype material concentration of holes in is very low. Actually, p n junction is fabricated by special technique, namely growing, alloying and diffusing methods. The impurity concentration is maximum at surface and decreases.
How a pn junction formed in a diode engineering tutorial. Initially we have a ptypentype semiconductor and we grow a thin ntypeptype layer on it. Silicon a single silicon atom consists of fourteen negatively. From xxnnpn da00 under reverse bias, vbi has to be replaced with vbivr.
Imaging the formation of a pn junction in a suspended carbon nanotube with scanning photocurrent microscopy. Formation of p n junction forward bias reverse bias p n junction formula formation of pn junction as we know, if we use different semiconductor materials to make a pn junction, there will be a grain boundary that would inhibit the movement of electrons from one side to the other by scattering the electrons and holes and thus we use the. Formation and properties of junction diode physics youtube. Formation of pn junction with chemical modification of. What is the currentvoltage characteristic for the pn junction diode. What happens when we join ptype and ntype semiconductors. This means that eventually in vicinity of the junction all free carriers will be.
Pn junction diode, characteristics and applications 2020. Specifically, current will flow readily in one direction forward biased but not in the other reverse biased, creating the basic diode. The elements and other things around us like copper,silver, gold, rubber, glass, water, oil etc are classified into conductors, semiconductors and insulators based on their. Pn and metalsemiconductor junctions the gmu ece department. At the instant of the pn junction formation, the free electrons near the junction in the n region begin to diffuse across the junction into the p region where they. Pn junction diode is one of the fundamental elements in electronics. If ptype semiconductor is joined with ntype semiconductor, a pn junction is formed.
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