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