It is the most essential and the basic building block of the electronic device. Let us also assume that all the donor atoms have donated free electrons and become positive donor ions and all the acceptor atoms have accepted electrons and created corresponding holes and become negative acceptor ions. Approximate solution using the full depletion approximation a abrupt pn junction an easy way to derive the depletion layer widths in a pn diode is to treat it as a combination of two schottky diodes, one with an ntype semiconductor and an other with a ptype. May 20, 2016 in this article, we will focus on the iv characteristics of the junction diode, specifically the pn junction.
A p n junction diode allows electric charges to flow in one direction, but not in the opposite direction. 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. This same diode and its characteristics are shown in figure 1. This is the basic construction of the p n junction diode. It is one of the simplest semiconductor devices as. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the p n junction. Alan doolittle 2 2 ln ln ln i a d bi a i d p n bi n n n q kt v n n n q kt n x n x q kt v movement of electrons and holes when forming the junction for nand1015cm3 in silicon at room temperature.
Vi characteristics of pn junction diode electronics post. Vi characteristics of pn junction diode in 3biasing modes. Jul 31, 2017 in this physics digital electronics video lecture in hindi for class 12 we explained forward and reverse bias in p n junction diode in terms of depletion layer and potential barrier. The p n junction is the fundamental building block of the electronic age. Pn junction diode and characteristics of pn junction diode. There are two operating regions and three possible biasing conditions for the standard junction diode and these are. If an external potential is applied to the terminals of pn junction, it will alter the potential between the p and nregions. Pn junction diode baising and its vi characteristics. Drainsource diode characteristics diode forward voltage note 3 v sd v gs0v,i s14a 1. A free powerpoint ppt presentation displayed as a flash slide show on id. Difference between pn junction diode and zener diode. Pn junction diode is one of the fundamental elements in electronics.
It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. According to the current continuity law, the current can only flow if all the charged particles move forming a closed loop. Pn junction diode and diode characteristics electronicstutorials. The boundary splitting the n and p region is referred to as the metaphysical junction. Like any diode, the pn junction diode has two connections or electrodes. Zero bias no external voltage potential is applied to the pn junction diode. The polarity shown, attracts holes to the left and electrons to the right.
When the diode is forwardbiased, it can be used in led lighting applications. Pnjunction diode characteristics ppt documentation. Change the saturation current and watch the changing of iv curve. A pn junction diode is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only. Iv characteristics uwhenever an electron on the pside moves to the nside, it is replaced by an electron generated through one of the rg centers ohmic ohmic minority minority excess majority carriers alocal excess majority carriers alocal e e excess carriers move to the contact with a relaxation time. The electrostatic analysis of a pn diode is of interest since it provides knowledge about the charge density and the electric field in the depletion region. We have seen the characteristics of pn junction diode through its graph. If we apply a reverse bias voltage to the diode, the depletion width increases and no charge can flow across the junction.
Silicon a single silicon atom consists of fourteen negatively. Diode dosimetry fordiode dosimetry for megggavoltage. To apply an external voltage, we usually connect 2 metallic contacts at the two ends of the pn junction known as terminals. 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.
The electrostatic analysis of a p n diode is of interest since it provides knowledge about the charge density and the electric field in the depletion region. Similarly, on the nside of the junction, using a boundary condition. The np product can be reduced below, as in a reverse biased junction n n p i 2 2 ni department of eecs university of california, berkeley eecs 105 spring 2004, lecture 19 prof. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction.
Consider a diode rectifier rated for v reverse bias. When one side of an intrinsic semiconductor is doped with acceptor i. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential currentvoltage iv relationship and therefore we can not described its operation by simply using an equation such as ohms law. Limitation of simple npn tunnel junction based leds grown. A p n junction diode is formed by doping one side of a piece of silicon with a ptype dopant boran and the other side with a n type dopant phosphorus. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential currentvoltage iv relationship. The diode equation gives an expression for the current through a diode as a function of voltage.
The o level exhibits a peak around the qws position, most likely due to the residual o found in the n 2 carrier. If the doping distribution in a pn junction is nonuniform, is the basic operation of the diode changed in a fundamental way. The credit of discovery of the p n junction goes to american physicist russel ohi of bell laboratories. Pn junction diode junction diode symbol and static iv characteristics. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. Real pn junction diode iv characteristics consider a diode. What are the depletion width in the nregion, the depletion width in the pregion, and the builtin potential at 300k. Note that although you can simply vary the temperature and ideality factor the resulting iv curves are misleading. In this physics digital electronics video lecture in hindi for class 12 we explained forward and reverse bias in pn junction diode in terms of depletion layer and potential barrier. In the normal rectifier grade pn junction diode, the junction is formed between p type semiconductor to n type semiconductor. P n junction is also a fundamental building block of many other semiconductor electronic devices such as transistors, solar cells, light emitting diodes, and integrated circuits. What is the difference between schottky diode and pn diode. Whereas in schottky diode the junction is in between n type semiconductor to metal plate. I 0 dark saturation current, the diode leakage current density in the absence of light.
Both the holes from pside and electrons from nside cross the junction simultaneously and constitute a forward current injected minority current due to holes. Normally the voltage is taken along the xaxis and current along yaxis. Drainsource diode characteristics diode forward voltage note 3 v sd vgs0v,is6a 1. The polarity shown, attracts electrons to the left and holes to the right. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. The horizontal line in the below figure represents the amount of voltage applied across the p n junction diode whereas the vertical line represents the amount of current flows in the p n junction diode. A perfect diode is a device that only allows current to flow through it in one direction, i. The pnjunction is the root for semiconductor diodes.
The diode is simple in its basic concept, being formed from the junction of n type and ptype materials, although in reality the manufacture and theory of operation are more complex. Physics of semiconductor devices pn junction depletion. 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. Lecture 16 the pn junction diode ii equivalent circuit model november 3, 2005 contents. The barrier increase reduces the majority carrier diffusion to a negligible level. At low current densities one can expect the pn diode to dominate the current flow, whereas at high current densities the nn. V applied voltage across the terminals of the diode. It conducts current linearly with increase in voltage applied across the 2 terminals provided the applied voltage crosses barrier potential. Voltampere characteristics of pn diode are studied. Difference between p n junction diode and zener diode definition of p n junction diode and zener diode diode is an electronic component that allows the flow of electricity in one direction without resistance or with very little resistance while in the opposite direction has an infinite or at least very high resistance. Calculate the resistance in forward bias and reverse bias. Let us consider a pn junction with a donor concentration n d and acceptor concentration n a. Lecture 15 the pn junction diode i iv characteristics november. Characteristics of junction diodes technical articles.
Identify the difference between the forward characteristic of a power diode and a signal. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. No generationrecombination in the depletion layer 6. 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 schottky barrier diode has electrons as majority carriers on both sides of the junction. The pn junction diode is a twoterminal device, which is formed when one side of the pn junction diode is made with ptype and doped with the ntype material. 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. 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 forwardbias and the reversebias properties of the p n junction imply that it can be used as a diode. Working of pn junction diode with biasing, characteristics. Image source forward biasing a pn junction diode is very simple. What happens to the cv characteristics, iv characteristics, and the dynamics of a pn diode with nonuniform doping dis tributions. Pn junction diode is the most fundamental and the simplest electronics device. The diode has two terminals called a cathode and an anode.
A pnjunction diode is formed when a ptype semiconductor is fused to an ntype semiconductor creating a potential barrier voltage across the diode junction. Abrupt depletion layer approximation let apply bias and calculate current through the pn junction currents in pn junction from sze, 1981. Real pn junction diode iv characteristics consider a. Difference between pn junction diode and zener diode definition of pn junction diode and zener diode diode is an electronic component that allows the flow of electricity in one direction without resistance or with very little resistance while in the opposite direction has. A pn junction is a boundary or interface between two types of semiconductor. 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 n side of the pn junction diode. If an external potential is applied to the terminals of pn junction, it will alter the potential between the p and n regions. P type and n type semiconductors, takenseparately are of very limited use.
It is also required to obtain the capacitancevoltage characteristics of the diode. Limitation of simple npn tunnel junction based leds grown by. A pn junction diode is formed by placing p and n type semiconductor. Substituting with boron boron, with five protons and five electrons, can also substitute in a silicon crystal where. The diode equation is plotted on the interactive graph below. The analysis is very similar to that of a metalsemiconductor junction. Voltampere vi characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. Under bias in scr, jdrift jdiff, but if difference small with respect to absolute values of current. Uniti diode current equation vi characteristics of pn junction. Pulse width limited by maximum junction temperature. Physical integrated structure p side intrinsic pn junction n. Pn junction diode characteristics electronic circuits and. Ppt pn junction diode powerpoint presentation free to. The pn junction is the fundamental building block of the electronic age.
The vi characteristics or voltagecurrent characteristics of the p n junction diode is shown in the below figure. The concentration of doping is same all over in every block. 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. A pn junction diode is formed when a ptype semiconductor is fused to an n type 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. What happens inside the pn junction diode when we apply forward bias. Jan 29, 2019 p n junction diode characteristics let us consider a pn junction with a donor concentration n d and acceptor concentration n a.
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