The pn junction is a versatile element, which can be used as a rectifier, as an isolation structure and as a voltagedependent capacitor. The pn junction when ptype and ntype semiconductors brought in contact with each other, we observe a drastically changed behavior and set of new properties, from the resulting device. A p n 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. This article provides a more detailed explanation of pn diode behavior than that found in the articles pn junction or diode. A zener diode when forward biased behaves like an ordinary pn junction diode. The p n junction has led to many inventions like the diode, transistors and integrated circuits. The contact surface between the layers of p type and n type semiconductor pieces plated together so as to form a p n junction is called the p n junction.
Direction of hole flow direction of conventional current c. The static and dynamic characteristics of a pn junction diode and zener diode characteristics. We can then fill in the junction region of the band diagram as. On the other hand, if the diode is reverse biased, it blocks the. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Pn junction diode and characteristics of pn junction diode. Why does the junction current in forward bias increase. The word diode can be explained as di means two and ode is obtained from electrode. The pn junction has led to many inventions like the diode, transistors and integrated circuits.
They are also called pn diodes in analogy with vacuum diodes. The arrow direction in the diode symbol indicates a. This page of application notes section covers pn junction diode applications. Photodetectors pn junction can detect light when reverse biased ptype ntype when the light illuminates the pn junction, the photons energy releases free electrons and holes.
A zener diode when forward biased behaves like an ordinary p n junction diode. The pn junction is a versatile element, which can be used as a rectifier, as an amplifier and as a voltageregulator and a switch. Pn junction diode and diode characteristics electronicstutorials. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Since the pn junction demonstrates such a unipolar rectifying response to the applied voltage it is called a pn diode and is denoted in circuit diagrams as a following symbol. They are also called p n diodes in analogy with vacuum diodes.
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. The pn junction diode principles of solar cells, leds and. A p n junction is the metallurgical boundary between the n and p regions of a semiconductor crystal. A pn diode is a type of semiconductor diode based upon the pn junction. A p n junction diode is a combination of two semiconductor materials, one is p type semiconductor and another is n type semiconductor. The p n junction is a versatile element, which can be used as a.
Free electrons on the n side and free holes on the pside can initially diffuse across the junction. Pn junction diode baising and its vi characteristics. The p n junction the p n junction is a homojunction between a p type and an n type semiconductor. A schottky junction is a special case of a pn junction, where metal serves the role of the ptype semiconductor. Pn junction diode is one of the fundamental elements in electronics. Pn junctions consist of two semiconductor regions of opposite type. Pn junction diode electronics club basic electronics. Reverse saturation current is frequently stated to be a drift current. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. A p n junction diode is formed by doping one side of a piece of silicon with a p type dopant boran and the other side with a n type dopant phosphorus. Questions you should be able to answer by the end of todays lecture. Contd notes and anderson2 sections part 2 preface and sections 5.
Such junctions show a pronounced rectifying behavior. The diode conducts current in only one direction, and it is made by joining a ptype semiconducting layer to an ntype semiconducting. Now lets try applying an external voltage to the pn junction diode. The diode has two terminals, ptype semiconductor is called. This note explains the concept and working of pn junction diode. The pn junction is the fundamental building block of the electronic age. Abrupt depletion layer approximation let apply bias and calculate current through the pn junction currents in pn junction from sze, 1981. The p n junction has been the most common rectifier used in the electronics industry. 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 contact surface between the layers of ptype and ntype semiconductor pieces plated together so as. A pn junction diode is a combination of two semiconductor materials, one is ptype semiconductor and another is ntype semiconductor. The p n junction is the fundamental building block of the electronic age. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode.
Objective the objective of this experiment is to measure the iv curve for pn junction diode and to understand the. If the electrons and holes were not charged, this diffusion process. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. This section will cover pn junction diodes, which are essential to solar cell operation. 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 n regions. The pn junction can be formed by allowing a ptype material to diffuse into a ntype region at high temperatures. A nega tive charge has the electric field lines point into it. Pn junction diode 1 ee105 fall 2014 microelectronic devices and circuits prof. Image source forward biasing a pn junction diode is very simple. 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.
The pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. A pn junction is the simplest form of the semiconductor diode. The objective of this experiment is to measure the iv curve for pn junction diode and to understand the characteristics of pn junction. Ee105 fall 2014 microelectronic devices and circuits. With the increase in applied external forward bias, the width of the depletion layer becomes thin and forward current in a pn junction diode starts to increase. Uniti diode current equation vi characteristics of pn junction. 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. 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. Reverse saturation current is frequently stated to be a. 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 p n junction is a versatile element, which can be used as a rectifier, as an isolation structure and as a voltagedependent capacitor. Similarly, holes flow by diffusion from the ptype side to the ntype side.
Octavian florescu 2 the pn junction diode schematic diagram p type n type id. No generationrecombination in the depletion layer 6. Definition, symbol, and types of diodes electrical4u. The name diode is derived from diode which means a device that has two electrodes.
P type and n type semiconductors, takenseparately are of very limited use. A pn junction of two different materials in the open circuit case. 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 diode has two terminals, p type semiconductor is called anode and n type semiconductor is called cathode. When the diode is forwardbiased, it can be used in led lighting applications. The pn junction diode principles of solar cells, leds. This article provides a more detailed explanation of pn diode behavior than that found in the articles pn junction or diode a pn diode is a type of semiconductor diode based upon the pn junction. Working of pn junction diode with biasing, characteristics. A pn junction diode is formed when a p type 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. The thicknesses of the depletion region are not the same with xn. It is also called as simply p n junction or semiconductor diode. 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. The pn junction has been the most common rectifier used in the electronics industry.
The p n junction can be formed by allowing a ptype material to diffuse into a n type region at high temperatures. It is acting as normal diode while forward biasing. When pn junction is reversed bias practically no current flows through it,but a very small current flows through due to minority charge carriers,which is known as saturation current or reverse saturation current. 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. A zener diode when reverse biased can either undergo avalanche break down or zener break down. 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. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor. Lecture 15 the pn junction diode i iv characteristics november. However, in a p n 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. 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.
For example, a common type of transistor, the bipolar junction transistor, consists of two pn junctions in series, in the form npn or pnp. If the diode is forward biased, it allows the electric current flow. A p n junction diode is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only. Zener diode is a p n junction diode specially designed to operate in the reverse biased mode. 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. This note explains the concept and working of p n junction diode. Silicon a single silicon atom consists of fourteen negatively. This is the basic construction of the p n junction diode. Why does the pn junction diode exhibit current rec tification. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the p n junction. Pn junction diode 2 diode introduction a diode is formed by joining an ntype semiconductor with a ptype semiconductor. Pn junction diode applications pn diode applications. They are referred to as photoelectrons and photoholes the applied voltage separates the photocarriers attracting electrons toward. The symbols for diodes and transistors use arrows to indi cate the direction that conventional current.
If both p side and n side of the diode are lightly doped, depletion region at the junction widens. Pn junction tutorial introduction to pn junction diodes. The direction of arrow is the direction of conventional current flow under forward bias. In the case of normal diodes the diode damages at the break down voltage. It is also called as simply pn junction or semiconductor diode. 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 acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode, switching or tuner varactor diode. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Pn junction vi characteristics voltagecurrent relationship for a pn junction diode note. Since a junction forms between a p type and n type material it is called as pn junction.
The objective of this experiment is to measure the iv curve for p n junction diode and to understand the characteristics of p n junction. Abrupt depletion layer approximation let apply bias and calculate current through the pn. On the n type side, positive ion cores are exposed. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. The more holes or free electrons there are, the more particles will diffuse across the junction. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. The pn junction is a versatile element, which can be used as a. When ntype and ptype dopants are introduced sideby side in a semiconductor, a pn junction or a diode is. A pn junction diode is made by forming a ptype region of material directly next to a ntype region. The diode conducts current in only one direction, and it is made by joining a ptype semiconducting layer to an ntype semiconducting layer semiconductor diodes have multiple uses. P n junctions consist of two semiconductor regions of opposite type.
A pnjunction diode is formed when a ptype semiconductor is fused to an ntype semiconductor creating a potential barrier voltage across the diode junction. This allows electrical current to pass through the junction only in. 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. 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. This pn diode applications are very useful for beginners. Free electrons on the nside and free holes on the pside can initially diffuse across the junction. 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. 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. If both pside and nside of the diode are lightly doped, depletion region at the junction widens.
135 1234 1002 1314 518 1184 1298 484 51 61 759 734 1093 1033 697 300 1057 1368 981 306 563 1189 1464 82 706 509 967 766 288 542 582 916 548 1341 302 72 30