Reverse resistance is defined as the resistance offered by the pn junction diode when it is reverse biased. Physics of pn junctions and semiconductor devices springerlink. This collection of laboratory exercises is the introductory physics laboratory manual used by hunter college. Youll also see how they control the direction of the. Pn junction one of the crucial keys to solid state electronics is the nature of the pn junction.
If the electrons and holes were not charged, this diffusion process. I mean the explanation i read in my books is like this. Pn junctions consist of two semiconductor regions of opposite type. 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.
A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Some physics topics are discussed in other appendices also. I some characteristics of the pin diode iregion since the presence of the relatively wide intrinsic layer in a pin diode is. Pdf experiment on the physics of the pn junction researchgate. A diode is a simple device, which can be implemented by a pnjunction, as well as other heterojunction structures.
Olav torheim, elementary physics of pn junctions, 2007. No electron move through the pnjunction at equilibrium state. Semiconductor device physics semiconductor device phenomenon is described and governed by poissons equation 1 d a s where n x n n p n q x, 2 2 1 is the effective doping concentration defined for the semiconductor, nx is the position dependent net doping density, nd is the donor. Reprints and other information can be found on the physics 111 library site lab 3 appendices. The potential barrier offers high resistance during.
Depletion approximation based quantitative solution for the electrostatic variables in a pn step junction under equilibrium conditions vb 0. Questions you should be able to answer by the end of todays lecture. Hitech gadgets, modern machinery, gigantic skyscrapers, speedy trains, superior infrastructure are some of the marvels of physics. So, 1when we forward bias the be junction in a bjt, does emitterbase current start before the collector current. It reveals the magic behind the wonderful existence of natural phenomenon. Pn junction diode is a two terminal device, the characteristics of diode depends on the polarity of the external potential applied to the pn junction diode. 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. An ideal junction in which there are no generationrecombination processes in depletion region. Diode allows current to pass in only one direction.
File type pdf semiconductor physics and devices solution manual semiconductor physics and devices solution manual introduction to semiconductor physics and devices in this video, i talk about the roadmap to learning semiconductor physics, and what the driving. Thus a pnjunction offers a low resistance when it is forward biased. Pn junction lab free to use on allows simulation and study of a pn junction diode with different doping and materials. You can check out and keep the portable breadboards, vb106 or vb108, from the 111lab for yourself only one each please. This is because the builtin potential across the depletion layer of the pn junction is high enough to prevent the majority carriers from returning once they cross the junction. Physics of semiconductor devices pn junction depletion. Dive into this lesson to learn about how the pn junction diode works and how it can be used. Full practical pn junction diode with readings, download pdf. Similarly, holes flow by diffusion from the ptype side to the ntype side. Physics of semiconductor devices pn junction depletion width problem.
The junction is the boundary or interface between these 2 types inside a single crystal of semiconductor. Bias is a potential applied dc voltage to a pn junction to obtain a desired. The majority charge carriers move away from the junction. P type and n type semiconductors, takenseparately are of very limited use. 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. Semiconductors, diodes, transistors horst wahl, quarknet presentation, june 2001 electrical conductivity. When a ptype and ntype material are brought in contact, a number of interesting properties arise.
Pn junction is formed in a single crystal by joining two ntype and ptype semiconductors. Specifically, current will flow readily in one direction forward biased but not in the other reverse biased, creating the basic diode. One of them has more donors than acceptors, and so it is. Minot1 1department of physics, oregon state university, corvallis, oregon 97331, usa 2istituto nanoscienze cnr, via campi 2a, i 41125 modena, italy. It is a substance with conduction properties between metals and insulators. Silicon solar cell top view showing collection grid and cross section. This pn junction forms a most popular semiconductor device known as diode. Physics is the study of matter and energy and the interaction between them. Concept of semiconductor physics department of physics. The concentrations of free carriers injected into the quasineutral regions are small enough so that we can. We will assume, unless stated otherwise, that the doped regions are uniformly doped and that the transition between the two regions is abrupt.
A physical switch that has this property is a pn junction diode. A pn junction is said to be forward biased when pregion is connected to positive terminal and nregion to the negative terminal of battery. Over 10 million scientific documents at your fingertips. Junction coming to the equilibrium by balancing the fermi level ef ef the balance is achieved by electrons diffusing into a pside bringing an extra negative charge in there and by the holes diffusing into an nside bringing an extra negative charge in there pn. What happens when we join ptype and ntype semiconductors. We will refer to this structure as an abrupt pn junction. If you continue browsing the site, you agree to the use of cookies on this website. Pdf lowenergy recombination radiation of pn junctions in gaas. The bipolar junction transistor as well as the field effect. Minot department of physics, oregon state university, corvallis, or, 97331, usa. A nanoscale pn junction in series with tunable schottky.
Doped semiconductors ntype materials ptype materials diodes and transistors. The pn junction is the fundamental building block of the electronic age. Pdf transient processes in semiconductor injection lasers with strong optical coupling. Pn junction is also a fundamental building block of many other semiconductor electronic devices such as transistors, solar cells, light emitting diodes, and integrated circuits. Diodes and transistors university of california, berkeley. Some fundamental questions about pn junctions physics forums. When ptype and ntype materials are placed in contact with each other, the junction behaves very differently than either type of material alone. A diode is a 2 lead semiconductor that acts as a one way gate to electron flow. Senger1, andrea bertoni2, vasili perebeinos3, ethan d. If the diode is forward biased, it allows the electric current flow. To really understand this, solid state physics is required. The baseemitter junction is biased in the forward direction so only the intrinsic voltage drop across a pn junction appears. Appendix b compares pin diode circuit characteristics to those of pnjunction devices. Higher physics second in a series of 3 videos on semiconductors.
Find materials for this course in the pages linked along the left. The charge in the depletion region per cross sectional area is the depletion width times the concentration of ionic charge qn. Because of its electrical properties, silicon is called a semiconductor. The pn junction in the interface layer between the ptype and ntype material, a nonconducting layer called the depletion region occurs. The original exercises were developed by the physics faculty over thirty years ago.
By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Frequently we will deal with pn junctions in which one side is. If the silicon crys tal is very pure, then the outer four electrons occupy all of the covalent. 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.
What are the depletion width in the nregion, the depletion width in the pregion, and the builtin potential at 300k. Device physics i pn junctions junction capacitance martin p. Silicon a single silicon atom consists of fourteen negatively. Connecting a pn junction to an external voltage source is biasing a pn junction. Such junctions show a pronounced rectifying behavior. But there are a few fundamental things which are still unclear to me and i am not very confident about my overall understanding of semiconductor physics. Class12 section contents certificate acknowledgement introduction applications summary bibliography certificate this is to certify that this project has been made by of class xii on zener diode under the guidance of our physics teacher ms and has been completed successfully. A pn junction consists of two semiinfinite semiconductors, which we imag ine to fill the entire space. 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. Derivation steps see extra file on web site for explanations. It is well known that semiconductor diodes exhibit shot noise. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Most semiconductor devices involve regions with two different kinds of doping, so a pnjunction is present in all of them. 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.
Appendix e discusses the topic of signal distortion in pin diodes. There are a few basic concepts to be introduced, such as energy bands, drift and diffusion currents, etc. This video covers the formation of the pn junction and how it performs when forward and reverse biased. 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. In particular, the revision of 1994 led by professor robert a.
In addition,lets make the following simplifying assumptions. Physics project pn junction semiconductors free 30day trial. They are also called pn diodes in analogy with vacuum diodes. Ms junctions can either berectifying or nonrectifying.