Pn junction diode and characteristics of pn junction diode. Coed school kolar road bhoapl department of physics project report investigatoryproject on pn junction and diodes project report submitted by govind patel submitted to mrs ratna hajela. A pnjunction diode is formed when a ptype semiconductor is fused to an ntype semiconductor creating a potential barrier voltage across the diode junction. Pn junction one of the crucial keys to solid state electronics is the nature of the pn junction. What is a pn junction when a ptype semiconductor is suitably joined to an ntype semiconductor, the contact surface is called pn junction. In a pn junction the potential barrier is due to the charges.
A pn junction is the basic building block of many semiconductor devices like diodes, transistor etc. The region in which the ptype and ntype semiconductors are joined is called pn junction. Semiconductor pn junction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. From the above, it follows that zero power dissipation occurs in an ideal diode. Working of pn junction diode with biasing, characteristics. Most semiconductor devices contains one or more pn junctions. 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. Semiconductor pn junction diode content writer epg pathshala. Mar 27, 2019 junction diodes questions and answers q1. The pnjunction obey the ohms law whereas zener diode does not obey the ohms law. A pn junction with open terminals excluding minority carriers f. A pnjunction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode. How a pn junction formed in a diode engineering tutorial.
Formation of depletion layer, barrier voltage and biasing. A pn junction is formed by diffusing a ptype material to an ntype wafer and there are several other ways as well, see your text. Pn junction theory for semiconductor diodes electronicstutorials. The ohms law said that the voltage applies across the diode is equal to the product of the current and resistance applied across the diodes. The pn junction solidstate device theory electronics. The word diode can be explained as di means two and ode is obtained from electrode. Imagine a pn junction with metallic contacts at both the ends for application of external voltage. By definition, ntype semiconductor has an excess of free electrons compared to the ptyp. This potential difference can alter the flow of majority carriers, so that the pn junction can be used as an opportunity for the diffusion of. In a pn junction with no external voltage, the electric field between acceptor and donor ions is called a. The main characteristic of a pnjunction or a diode is that for positive voltages. 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. The pn junction has the very useful property that electrons are only able to flow in one direction.
Electrons and holes diffuse into regions with lower concentrations of electrons and holes, much as ink diffuses into water until it is uniformly distributed. Although it is not discussed majorly outside the concept of pn junction diode and sometimes the transistor, a pn junction is an essential topic in semiconductor electronics. Doped semiconductors ntype materials ptype materials diodes and transistors. This presentation is a very informative piece on pn junction diode an important part of electronics education. It is acting as normal diode while forward biasing. Lecture 15 the pn junction diode i mit opencourseware. If we join ptype semiconductor with ntype semiconductor such that the crystal structure remains continuous at the boundary, then junction formed in between them is. The p side is called as anode and n side is called as cathode. Pn junction diode applications pn diode applications. We can then fill in the junction region of the band diagram as. 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 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.
This recombination of electrons and holes produces a narrow region at junction called depletion layer. The pn junction is a versatile element, which can be used as a. Questions you should be able to answer by the end of todays lecture. Semiconductor, silicon, pn junction, forward bias, reverse bias, diode. 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. Zero bias no external voltage potential is applied to the pn junction diode. Here you may find a good video with animation, which explains the formation of pn junction. The term junction refers to the boundary interface where the two regions of the semiconductor meet. Pn junction diode multiple choice questions answers. Pn junction diode in the reversebiased configuration is sensitive to light from a range between 400nm to nm, which includes visible light. Formation of pn junction in actual practice, a pn junction will not be formed if. A pn junction diode is a two terminal single crystal semiconductor device whose one side is doped with acceptors and other side by donors.
It is also important to note here that the equilibrium barrier potential can be altered. The zener diode working principles and its various. May 17, 2020 a pn junction is the simplest form of the semiconductor diode. Pnjunction diode and diode circuits 1 main properties of semiconductors 2 the pnjunction in equilibrium 3 the i v characteristics of the pnjunction 4 deviations from the ideal diode 5 analysis of the diode circuits 6 rectifier circuits. A semiconductor diode is a two terminal electronic component with a pn junction. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. A pn junction diode is a twoterminal electronics element, which can be classified as either. Pn junction underbiasing 14 boltzmanns approximation. This allows electrical current to pass through the junction only in. If ptype semiconductor is joined with ntype semiconductor, a pn junction is formed. If an external potential is applied to the terminals of pn junction, it will alter the potential between the p and nregions.
The arrow direction in the diode symbol indicates a. A pn junction aggregates the recombination, generation, diffusion and drift effects described in the previous pages into a single device. A pn junction is a boundary or interface between two types of semiconductor materials, ptype. They are also called pn diodes in analogy with vacuum diodes.
In this video, the pn junction diode has been explained. Since a junction forms between a p type and n type material it is called as pn junction. A pn junction at equilibrium is characterized by a depletion region where there are no charge. Octavian florescu 2 the pn junction diode schematic diagram ptype ntype id. Pn junction diode baising and its vi characteristics. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Semiconductors, diodes, transistors horst wahl, quarknet presentation, june 2001 electrical conductivity. The pn junction is of great importance as it is the main control element for the semiconductor devices. For the love of physics walter lewin may 16, 2011 duration. 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. Silicon wafer cleaning rca process in the ic processing wafers it is necessary to maintain the purity and perfection of material.
Pn junction tutorial introduction to pn junction diodes. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Pn junctions consist of two semiconductor regions of opposite type. It is one of the simplest semiconductor devices as it allows current to flow in only one direction. The boltzmann approximation is to say that the resulting current being small compared with the components of. In the case of normal diodes the diode damages at the break down voltage. P type and n type semiconductors, takenseparately are of very limited use. 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. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. It is used for many forms of rectification for current levels both large and small, as well as high and low voltage levels, and it finds many uses in all manner of electronic circuits.
Read more pn junction diode and its working principle. Draw the energy level diagram of a pn junction and explain how a junction barrier is developed across an unbiased junction. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Direction of hole flow direction of conventional current c. This value is proportional to the crosssectional area of the pn junction. Specifically, current will flow readily in one direction forward biased but not in the other reverse biased, creating the basic diode. And the working of this pn junction diode under forward and reverse bias has been. Convert a part of the ptype semiconductor into ntype silicon semiconductor by adding a small quantity of pentavalent impurity. Diode is a basic element in electronic and digital circuit. At the point of the junction, which we call the metallurgical junction, is where n d n a 0. In this paper formation a pn junction diode is explained by vlsi fabrication steps which are stated below. Pdf defect analysis in semiconductor materials based on pn. After having known about various components, let us focus on another important component in the field of electronics, known as a diode. Zener diodes are normal pn junction diodes operating in a reversebiased condition.
In a pn junction, when the electrons and holes move to the other side of the junction, they leave behind exposed charges on dopant atom sites, which are fixed in the crystal lattice and are unable to move. How is a depletion layer formed in a pn junction diode. For information about citing these materials or our terms of use, visit. 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. Silicon a single silicon atom consists of fourteen negatively. The pn junction forms a basic semiconductor device called diode. The pn junction is the fundamental building block of the electronic age. It will help you to grasp concepts behind pn junction even better. Pn junction diode is one of the fundamental elements in electronics. Pn junction diode, characteristics and applications 2020. The diode conducts when forward bias is applied and it will introduce zero resistance in the circuit.
Fabrication of pnjunction diode by icfabrication process. Forward bias current flows reverse bias no current flow. Sangeeta semwal, ministry of electronics and information technology. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor. If the positive terminal of the battery is connected to the ptype semiconductor and the negative terminal of the battery is connected to the ntype semiconductor, the diode is said to be in forward bias. When the diode is forwardbiased, it can be used in led lighting applications. Explain the formation of potential barrier and depletion layer. Lecture 16 the pn junction diode ii equivalent circuit model november 3, 2005 contents. Junction diodes questions and answers electronics post. The anode which is the positive terminal of a diode is represented with a and the cathode.
Semiconductor physics semiconductors and diodessemiconductors. This pn diode applications are very useful for beginners. This pn junction separates ntype semiconductor from ptype semiconductor fig. The pn junction diode is the basic semiconductor diode format. So, in this pn junction tutorial, we will discuss some of the basics of a pn junction, how a pn junction is formed, characteristics of pn junction and many other aspects. 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. The energy band information is summarized in figure 10. For discrete diodes, the reverse saturation current is usually at i s 10 na. V t 25 mv important note unless otherwise stated, we will assume that each and every junction diode is at room. Working of the zener diode is similar to a pn junction diode in forwarding biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its thresholdbreakdown voltage. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. The indispensable operation in semiconductor diode is the basis for understanding of all the semiconductor diodes.
A pn junction is a junction formed by joining ptype and ntype semiconductors together in very close contact. This potential difference can alter the flow of majority carriers, so that the pn junction can be used as an opportunity for the diffusion of electrons and holes. Cbse ncert notes class 12 physics semiconductor electronics. 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 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. Specialpurpose diodes 129 actually contain two pn junctions that are connected in reverseparallel i. Engineering the minority carrier injection across a junction. Why is silicon preferred over germanium in the manufacture of semiconductor devices. The recombination at the junction allows battery current to flow through the pn junction diode. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. On the other hand, if the diode is reverse biased, it blocks the. The pnjunction diode is mainly used for rectification purpose, whereas the zener diode is used for providing the. I have developed a second chapter on the series, which explains the characteristics of pn junction diode.
A pn junction is the simplest form of the semiconductor diode. The name diode is derived from diode which means a device that has two electrodes. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Doping with acceptor creates p type semiconductor while doping with donors produces n type. Since the ntype region has a high electron concentration and the ptype a high hole concentration, electrons diffuse from the ntype side to the ptype side. Additional defect information has also been gained from other wellknown. The pn junction is the basis for diodes, certain transistors, solar cells, and other devices. The potential at terminal x with respect to y will vary as a sine function with time. Such junctions show a pronounced rectifying behavior. If the electrons and holes were not charged, this diffusion process.
The contact surface between the layers of ptype and ntype semiconductor pieces plated together so as to form a pn junction is called the pn junction. Pn junction diode explained forward bias and reverse bias. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Investigation of a barrier layer by the thermoprobe method pdf. In the positive half cycle, during the time interval 0 to t2, diode d will be forward biased and conduct, i. Therefore, for pnjunctions in ics, the reverse saturation current is much lower. The load resistance r l is connected to these terminals through a pn junction diode d. When ptype and ntype materials are placed in contact with each other, the junction behaves very differently than either type of material alone. As the depletion layer built up a different of potential appears across the junction this difference of potential at junction is called potential barrier. 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. If the diode is forward biased, it allows the electric current flow. This is the symbolical representation of a semiconductor diode in the image above, the arrow indicates the direction of current when the diode is under forward bias. If positive potential is applied to the top terminal as shown in fig.
This page of application notes section covers pn junction diode applications. The pn junction biasing the pn junction the diode trouble shooting. Apr 05, 2019 working of pn junction diode if an external potential is applied to the terminals of pn junction, it will alter the potential between the p and nregions. This is the basic construction of the pn junction diode. Definition, symbol, and types of diodes electrical4u. A ptype material consists of silicon atoms and trivalent impurity atoms such as. Pn junction diode and diode characteristics electronicstutorials. The valence band and conduction band in ntype material are slightly lower than that of ptype material. Image source forward biasing a pn junction diode is very simple.
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