In chemistry, the law of mass action is the proposition that the rate of a chemical reaction is directly proportional to the product of the activities or concentrations of the reactants. Equilibrium carrier concentration engineering libretexts. The law of mass action is applied for both intrinsic and extrinsic semiconductors. Impurity atoms act as either donors or acceptors to the intrinsic semiconduc. We introduce the mass action law by using a general chemical reaction equation in which reactants \\cea\ and \\ceb\ react to give products \\ cec \ and \\ced\. The existing competing books by indian authors have too complex technical language which makes them abstractive to indian students who use english as their secondary language. My book says that if a pure semiconductor is doped with ntype impurities, the number of electrons in the conduction band increases above a level and the number of holes decreases below a level. This law is also applicable to semiconductors and, therefore, has several important implications in the fields of electronics and semiconductor physics. It explains and predicts behaviors of solutions in dynamic equilibrium.
Pdf mass action and conservation of current researchgate. Draft material for fundamentals of plasma physics book. Apart from this, there is also atomic physics that deals with subatomic particles and their interactions quantum mechanics. The law of mass action governing the relative concentrations of electrons and holes in a semiconductor is given by np 4 k57 memnzexp where all the terms have the usual meaning. The law of mass action for intrinsic semiconductors is. The reason why your mental image of a semiconductor doesnt really help here, is because its actually impossible to distinguish whether a free. Any of various solid crystalline substances, such as germanium or silicon, having electrical conductivity greater than insulators but less than good. This video is about mass action law in semiconductors. In electronics and semiconductor physics, the law of mass action is a relation about the concentrations of free electrons and electron holes under thermal equilibrium. A typical semiconductors conductivity the degree to which it conducts electricity depends on imperfections in the material such as lattice defects, added impurities, and external conditions such as applied electric fields. Mass action law in semiconductors law of mass action hd.
Einstein relationship semiconductor physics and radio. Lets discuss the intrinsic case first undoped semiconductor. One diode can be used as a halfwave rectifier or four as a fullwave rectifier. In a semiconductor the law of mass action states that the product of the electron concentration and the hole concentration is always equal to the square of the intrinsic carrier concentration at a given temperature, i. Impurity atoms are atoms of a different element than the atoms of the intrinsic semiconductor. Msc physics entrance exam 201920 semiconductor,drift. A semiconductor device which conducts electric current run in one direction only. Similarly, the addition of ptype impurities to a pure semiconductor increases the number of holes in the valence band above a level and decreases the number of electrons in the conduction band below a level. In electronics and semiconductor physics, the law of mass action is a relation about the concentrations of free electrons and electron holes under thermal. However, for reactions that are complete, the result may not be very useful. When an atom is in a solid, these energy levels are smeared out into bands. Here three gate problems related to the concept of mass action law are discussed.
Writing a book on semiconductor device physics and design is never complete and probably never completely satisfying. Semiconductor physics and materialsintrinsic and extrinsic semiconductors, conduction mechanism in extrinsic semiconductors, carrier concentrations, drift and diffusion mechanisms, drift and diffusion current densities, excess carriers, recombination process, mean carrier lifetime, conductivity, mobility, mass action law, einstein relationship. Physics is an essential subject for cbse 12th science stream. Laws of physics and applications of all physics laws byjus. The majority carriers are holes and minority carriers are electrons. Shur was my teacher and masters advisor at rpi, and i took two semesters of graduatelevel semiconductor devices with him. So why does an ntype material conducts better than a an intrinsic semiconductor presumably they have same. Pdf the law of mass action does not force a series of chemical reactions to have the same current flow. His book physics of semiconductor devices wiley 1969, 2nd ed, 1981 is the most cited work in contemporary engineering and applied science publications over 12,000 citations from isi press. Sociophysics social physics mathematical epidemiology. This law states the relation between concentrations of minority and majority carriers at a constant temperature.
Currently this section contains no detailed description for the page, will update this page soon. Ohms law is the basic rule of electricity explains the relationship between electric current, voltage, and resistance. This book is an introduction to the principles of semiconductor physics, linking its scientific aspects with practical applications. My book states that this law is valid for extrinsic semiconductors with impurities as well as for intrinsic semiconductors. Mathematics medicine physics social sciences statistics workforce. Physics 301 30nov2005 261 semiconductor basics in solids, the electron energy levels are organized into bands.
An introduction advanced texts in physics seeger, karlheinz on. During doping, impurity atoms are introduced to an intrinsic semiconductor. Devices made from semiconductor materials are the foundation of modern electronics, including ratio, computers. Einstein relationship semiconductor mobility characterizes how quickly an electron or hole can move through a semiconductor, when electric field is applied to it. Solid state physics 9788121914765 by v k babbar and a great selection of similar new, used and collectible books available now at great prices. Basic laws of physics that govern our universe can be categorized in two ways. Engineering physics agricultural engineering pdf book. In a semiconductor material intrinsic or extrinsic, the law of mass action. Typically, the dopant concentration is at least 47 orders of magnitude 107 larger than the intrinsic concentration. This video is the first one dealing with gate problems in semiconductor physics. This law has significant importance in semiconductor physics. This is a great book with more advanced coverage than most of the undergraduate device physics books. What is the theory behind mass action law in doped. The law of mass action is very important in semiconductor physics, and although i believe the maths to be exactly the same, the application is quite different.
File type pdf semiconductor physics and devices solution manual. Let a bar of silicon have an intrinsic concentration of 1010 cm3. The process of electrons or holes moving from the higher concentration region to the lower concentration region is called diffusion. Topics related to basic impurity theory include the hydrogenic model for shallow impurities, linear screening, density of states, classical and quantum statistics, the law of mass action, as well as many analytic approximations for the fermidirac integral for three, two and one dimensional systems. The equation is true for both intrinsic and extrinsic semiconductors and tells 2 important facts about extrinsic semiconductors.
For ntype semiconductor, the law of mass relation can be written as n n 1 for ptype semiconductor, the law of mass relation can be written as. Electrons in an isolated atom can only occupy discrete energy levels. When an intrinsic semiconductor is doped with a dopor impurity like phosphorus, electron concentration will increase, due to the surplus electron provided by each of the doper atom. Imagine a regular crystal lattice composed of identical atoms. It is addressed to both readers who wish to learn semiconductor physics and those seeking to understand semiconductor devices. Now dope it with a donor of concentration 1016 cm3. The conductivity of a semiconductor material can be varied under an external electric field.
The ohms law was named after the german physicist georg ohm who discovered this rule or law. He has authored or coauthored over 150 technical papers, and has written, edited, and contributed to 24 books. The law of mass action also has applications in the following fields. Solid state physics forms an important part of the undergraduate syllabi of physics in most of the universities. Is the principle of mass action law applicable in a pn. Here, the law of mass action provides a relationship between the concentrations of electron holes and free electrons when the semiconductor system is in a state of thermal equilibrium. The definition of mass action law, along with its mathematical. It is a very important subject for the various entrance exams for engineering, medical, or other higher education in the future. Massaction law of semiconductors electrical engineering. Semiconductor physics synonyms, semiconductor physics pronunciation, semiconductor physics translation, english dictionary definition of semiconductor physics. Lawofmass action relates concentration of reactants. Cbse syllabus for class 12 physics 20192020 pdf physics.
You will learn here the basics of law of mass action in semiconductors. The law of mass action states that the product of number of electrons in the conduction band and the number of holes in the valence band is constant at a fixed temperature and is independent of amount of donor and acceptor impurity added. The law of mass action is universal, applicable under any circumstance. Problem solutions archives page 2 of 3 free gate ece. Classical physics that deals with us, the surrounding environment and the observable universe around us. Why n and p are not additive in law of mass action. Ive added a stub of a section for that, but if someone more knowledgeable than me could extend it, i. A ptype semiconductor is formed by doping the silicon crystal with elements of group iii of the periodic table aluminum, boron, gallium, and indium.
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