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. Abrupt depletion layer approximation let apply bias and calculate current through the pn. 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. Under bias in scr, jdrift jdiff, but if difference small with respect to absolute values of current. The pn junction is a versatile element, which can be used as a. 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. They are referred to as photoelectrons and photoholes the applied voltage separates the photocarriers attracting electrons toward. Lets now get back to the equilibrium condition and start to analyze the junction.
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. Pn junction diode and characteristics of pn junction diode. Similarly, holes flow by diffusion from the ptype side to the ntype side. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. If the leakage current flowing across the basecollector junction of an npn. 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. A ptype has a lot of holes and an ntype lot of electrons. Pdf carbon nanotube pn junction diodes researchgate. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Such junctions show a pronounced rectifying behavior.
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. This shows that pn junctions behave like diodes, rectifying the current flow. What are the depletion width in the nregion, the depletion width in the pregion, and the builtin potential at 300k. 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. Diodes and transistors under high localized pressure technische. 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. The diode is simple in its basic concept, being formed from the junction of ntype and ptype materials, although in reality the manufacture and theory of operation are more complex. 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. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Consider a diode rectifier rated for v reverse bias. P type and n type semiconductors, takenseparately are of very limited use. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. The forwardbiased pn junction if a positive voltage is applied to the pelectrode relative to the.
The electric field opposes the diffusion of holes in the n region and free electrons in the p region. Spring 2003 ee lecture 10, slide 4 idealized junctions. 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. 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. Pn junction diode and diode characteristics electronicstutorials. If an external potential is applied to the terminals of pn junction, it will alter the potential between the p and nregions. Pn junction tutorial introduction to pn junction diodes. The fusion of these two diodes produces a three layer, two junction. No generationrecombination in the depletion layer 6. 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. The pn junction is the fundamental building block of the electronic age.
Publishers pdf, also known as version of record includes final page, issue and. Pn junctions consist of two semiconductor regions of opposite type. 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. Physics of semiconductor devices pn junction depletion. Difference between pn junction diode and zener diode. 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 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. Pn junction diode is one of the fundamental elements in electronics. In this video, lets explore the famous pn junction.
They are also called pn diodes in analogy with vacuum diodes. Gilbert ece 340 lecture 27 102912 zener breakdown last time we talked about zener breakdown the zener effect is the breakdown mechanism if the reverse bias required to force breakdown occurs at low voltages. 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. The barrier increase reduces the majority carrier diffusion to a negligible level. 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. A pn junction diode in thermal equilibrium you have already seen a pn junction diode in thermal equilibrium. To apply an external voltage, we usually connect 2 metallic contacts at the two ends of the pn junction known as terminals. 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. Diodes and thyristors a diode one way valve is a pn junction with ptype on one side and ntype on the other. If the electrons and holes were not charged, this diffusion process.
A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. Real pn junction diode iv characteristics consider a. Pn and metalsemiconductor junctions the gmu ece department. Lecture 15 the pn junction diode i iv characteristics november 1, 2005 contents. Image source forward biasing a pn junction diode is very simple. Silicon a single silicon atom consists of fourteen negatively. We will see what happens when we have a single crystal with a ptype semiconductor on one side and an ntype on the other. Working of pn junction diode with biasing, characteristics. The hetero pn junction the heterojunction n diode is in principle very similar to a homojunction. The pn junction is one of the primary building blocks of semiconductors. 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. Lecture 15 the pn junction diode i iv characteristics november.
Converting a layer of an ntype semiconductor into p type with acceptors would also create. If i short terminals of pn junction diode, does current flow on the outside circuit. Like any diode, the pn junction diode has two connections or electrodes. Lecture 6 biased pn junction diodes and current flow.
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