The diode uses the properties caused by the depletion area of the junction. The pn junction the diode is the simplest bipolar semiconductor dev ice. Their values depend on the individual doping concentrations forward biasing the junction shrinks the depletion width and the barrier, allowing thermionic emission and higher current. Chapter 4 pn junctions pn junction is present in perhaps every semiconductor device. This yields the socalled flatband diagram shown in figure 4. In semiconductor physics, the depletion region, also called depletion layer, depletion zone. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. There are a few basic concepts to be introduced, such as energy bands, drift and diffusion currents, etc. An abrupt silicon pn junction n a 10 16 cm3 and n d 4 x 10 16 cm3 is biased with v a 0. Special fabrication techniques are adopted to form a p n junction 4.
Substituting with boron boron, with five protons and five electrons, can also substitute in a silicon crystal where. Xiaojing feng1,2, xing zhao1,3, liu yang1, mengyao li1,4, fengxiang qie1, jiahui guo1,4, yuchun. Pdf barrier potential across semiconductor pn junction and. Pn junction in thermal equilibrium if no external stimulus is applied zero applied voltage, no external light source, etc the device will eventually reach a. A pn junction with open terminals excluding minority carriers f. A bipolar junction diode is basically a pn junction with conducting terminals attached to each side of the junction. Therefore, the region around the junction will contain no free. As the depletion area has very few free chargecarries it acts effectively as an insulator. Metaloxidesemiconductor structure on ptype silicon.
The most common type of semiconductor diode is the silicon diode. The region on the left is ptype with an acceptor density n a, while the region on the right is ntype with a donor density n d. This demonstration shows the electronic band structure, above, of a pn junction as well as the physical junction, below, for a generic semiconductor. I have developed a second chapter on the series, which explains the characteristics of pn junction diode. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Pn junction diode and characteristics of pn junction diode. Band structure of open circuted pn junction youtube. Pn junction diode is one of the fundamental elements in electronics. An abrupt silicon n i 10 10 cm3 pn junction consists of a ptype region containing 10 16 cm3 acceptors and an ntype region containing 5 x 10 16 cm3 donors. What is a pn junction when a ptype semiconductor is suitably joined to an ntype semiconductor, the contact surface is called pn junction. The fermi level lies close to the conduction band in ntype material and it is close to valence band in ptype material. At this coupling point, free electrons ntype and holes ptype cancel each other and form a depletion zone that acts as a nonconductive barrier.
In conventional semiconductors, a pn junction produces depletion regions of free charge carriers at equilibrium and builtin potentials associated with. Simplified physical structure construction on a cmos chip. Most semiconductor devices involve regions with two different kinds of doping, so a pn junction is present in all of them. If a free electron in the p region or a hole in the n region somehow reach the. The structure and energy band model of a pn junction in equilibrium when the junction reaches equilibrium, further diffusion is inhibited by the coulomb force between the newly created negative ions and the electrons. The peak electric field in the space charge region of pn junction is quite large.
We will see what happens when we have a single crystal with a ptype semiconductor on one side and an ntype on the other. The hetero pn junction the heterojunction n diode is in principle very similar to a homojunction. Electronics tutorial about the pn junction diode and the vi characteristics of pn. Pn junction diode applications pn diode applications. Pn junction article about pn junction by the free dictionary.
The pn junction is of great importance as it is the main control element for the semiconductor devices. Review, pn junctions, fermi levels, forward bias prof j. Semiconductors pn junction theory interview questions and answers pdf free download. This page of application notes section covers pn junction diode applications. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. We present results from a pn junction device physics model for gainpgaasgainaspgainas four junction solar cells. Pdf pn junction heterostructure device physics model of. This pn diode applications are very useful for beginners. The pn junction fundamentals semiconductor technology. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. Pn junction the interface at which ptype silicon and ntype silicon make contact with each other. Smith department of eecs university of california, berkeley eecs 105 spring 2004, lecture 19 prof. 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.
Pn junction tutorial introduction to pn junction diodes. Lecture 4 pn junction and mos electrostatics i semiconductor electrostatics in thermal equilibrium september 20, 2005 contents. Such junctions show a pronounced rectifying behavior. Shockley model from sze, 1981 vv at 1 j j e tot s n n p p p n s l d n q l d p j 0 0 j j x j x tot n p p n a i n n n d n q 2 w p n. A pn junction is usually rated in terms of its peak inverse voltage or piv. Band structure of open circuted pn junction study buddy.
A diode is a simple device, which can be implemented by a pn junction, as well as other hetero junction structures. Band structure of pn junction semiconductor wolfram. Investigation of a barrier layer by the thermoprobe method pdf. Pn junction diode 1 ee105 fall 2014 microelectronic devices and circuits prof. Forming a pn junction doping one side of a piece of silicon with boron a ptype dopant and the other side with. This demonstration shows the electronic band structure, above, of a pn. A pn junction consists of two semiconductor regions with opposite doping type as shown in figure 4. The pn junction at equilibrium and with applied voltage. Semiconductor pnjunction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. The bipolar transistor transfer resistor is one of the most important semiconductor. In this video, lets explore the famous pn junction. Band structure of pn junction semiconductor youtube.
The pn junction weve seen that it is possible to turn a crystal of pure silicon into a moderately good electrical conductor by adding an impurity such as arsenic or phosphorus for an ntype semiconductor or aluminum or gallium for a ptype semiconductor. Pn junction lab free to use on allows simulation and study of a pn junction diode with different doping and materials. 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. At the junction, the free electrons in the ntype are attracted to the positive. Introduction to semiconductors and the pn junction diode. Lecture 15 the pn junction diode i mit opencourseware. Sep 10, 2016 pn junction and zener diode 12 class project.
The dopants are assumed to be shallow, so that the electron hole density in the ntype ptype region is approximately equal to the donor acceptor density. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Lecture 15 the pn junction diode i free online course. Lecture pn junction and mos mit opencourseware free. Diodes are electronic check valves which allow current to flow freely in one direction, but block current flow in the opposite direction. The panels show energy band diagram, electric field, and net charge density. Barrier potential across semiconductor pn junction and resting membrane potential. Calculate the total width of the depletion region if the applied voltage v a equals 0, 0. An extra electron jumps into the conduction band and gets free.
Pn junction free download as powerpoint presentation. Switching transient switching transient the pn junction diode can be used as an electrical since. Pn junctions are types of semiconductors with a unique band structure and are used in variety of applications from solar cells to leds to transistors. Najmabadi, ece65, winter 2012 high concentration of h on the p side holes diffuse towards the junction high concentration of. The wolfram demonstrations project contains thousands of free interactive visualizations, with new entries added daily. Most semiconductor devices contains one or more pn junctions. The depletion region extends further into the lowerdoped region. The pn junction diode may get destroyed due to excessive heat if any of these values are exceeded. In a ptype boron doped silicon crystal the corresponding holes will become equally distributed throughout the ptype crystals volume. Silicon a single silicon atom consists of fourteen negatively.
The pn junction provides satisfactory performance when operated within these limiting values. Therefore, the region around the junction will contain no free carriers and is considered depleted. 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. Aug 01, 2016 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. By definition, the ntype semiconductor has an excess of free electrons in the. The electrical characteristics of leds are the same as normal. Semiconductor pn junction diodes can be formed from materials other than silicon, such as germanium, selenium, and a host of semiconductor materials used in. Band diagram and carrier distribution of pnjunction. A large density gradient in both the hole and electron concentrations occurs across this junction. Nonuniformly doped semiconductor in thermal equilibrium 2. Pn junction diode 2 diode introduction a diode is formed by joining an ntype semiconductor with a ptype semiconductor.
Suppose that two blocks of semiconductor of opposite extrinsic doping, i. Apr 07, 20 because it gives rise to discontinuities across the crystal structure. Pn junction in thermal equilibrium if no external stimulus is applied zero applied voltage, no external light source, etc the device will eventually reach a steady state status of thermal equilibrium in this state open circuit and steady state condition the current density must be zero. A pn junction is an interface or a boundary between two semiconductor material types, namely the ptype and the ntype, inside a semiconductor. Calculate the builtin potential of this pn junction. In this video, i go over the band diagram of the pn junction, which will allow us to find the electric field and the pn junction width through what is called the builtin potential vbi. Shockley model from sze, 1981 vv at 1 j j e tot s n n p p p n s l d n q l d p j 0 0 j j x j x. The pn junction diode is the basic semiconductor diode format. The main problemp that needs to be tackled is he effect of the bandgap discontinuities and the different materialt parameters, which make the actual calculations more complex even though the n diode p concepts need almost no changing.
Module 2 essentially, they serve the same function in circuits, as the valves in your heart and. Ee105 fall 2014 microelectronic devices and circuits. Module 1 semiconductor pnjunction diodes what are they and what is their purpose. Pn junction diode and diode characteristics electronicstutorials.
When a pn diode is made with ptype and ntype materials, then flow of free charge carriers takes place at the junction. 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 registerationno. The pn junction is a versatile element, which can be used as a. Lecture 15 the pn junction diode i iv characteristics november 1, 2005 contents. 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. 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. 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. Electrical behavior of pnjunctions to consider what happens electrically in a pnjunction, one can, again, consider a thought experiment. Because it gives rise to discontinuities across the crystal structure. Pn junctions ece 663 in summary a pn junction at equilibrium sees a depletion width and a builtin potential barrier. The result is that some of the free electrons from the donor impurity atoms begi. In a nside region near to the junction interface, free electrons in the conduction band are. Objective determine the properties of a pn junction including the ideal currentvoltage characteristics of the pn junction diode the equilibrium pn junction figure a is a simplified block diagram of a pn junction.
The pn junction electronics assignment help and homework help. Jul 09, 2012 the wolfram demonstrations project contains thousands of free interactive visualizations, with new entries added daily. If there is a doping gradient in a semiconductor, what is the resulting majority carrier concentration in ther. Energy band diagram2, fermi energy level electronic devices2 by sahav singh yadav duration. Introduction to semiconductors and the pn junction diode robert clancy 04329741 april 10, 2006 abstract in this experiment the iv characteristicof the pn junction diode is determined andthe applicationofthe diodeasarecti. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. Electrical behavior of pn junctions to consider what happens electrically in a pn junction, one can, again, consider a thought experiment. Pn junctions consist of two semiconductor regions of opposite type. 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. It will help you to grasp concepts behind pn junction even better. To reach thermal equilibrium, electronsholes close to the metallurgical junction diffuse across the junction into the ptypentype region where hardly any electronsholes are present. The pn junction has the very useful property that electrons are only able to flow in one direction. 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.
The pn junction electronics assignment help and homework. Calculate the ideal diode current assuming that the ntype region is much smaller than the diffusion length with w n 1 mm and assuming a long ptype region. A pn junction is a boundary or interface between two types of semiconductor materials, ptype. 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. The pside or the positive side of the semiconductor has an excess of holes and the nside or the negative side has an excess of electrons. A pn junction is a device formed by joining ptype doped with b, al with ntype doped with p, as, sb semiconductors and separated by a thin junction is called pn junction diode or. Objective questions on pn junction diode electrical. The pn junction is the fundamental building block of the electronic age. Basically, in this type of transistor construction the two diodes are reversed with respect to the npn type giving a positivenegativepositive type of configuration, with the arrow which also defines the emitter terminal this time pointing inward. A ptype has a lot of holes and an ntype lot of electrons. It comprises ptype and ntype semiconductor materials brought together, usually after diffusion or im plantation, to form a step or abrupt junction as. Volume ii 2nd edition modular series on solid state dev. The interface at x 0 is called the metallurgical junction. This process leaves the ionized donors acceptors behind, creating a region around the junction, which is depleted of mobile carriers.
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