Ptype, ntype semiconductors engineering libretexts. Calculate maximum electric field in the depletion region at 0, 0. Fermi level lies in between valence and conduction bands. Wheter you get an energy in form of a photon light or not depends on the semiconductor. In p type semiconductors, holes are the majority carriers and electrons are the minority carriers. For a p type semiconductor, there are more holes in the valence band than there are electrons in the conduction band. The exact character of the semiconductor can be changed by varying the amount of dopant that is added. A p type semiconductor is one with a preponderance of holes. No bias v0 absence of external voltage across the p n junction is called the unbiased diode. The p type dopant, an electron acceptor, yields localized regions of positive charge known as holes.
As conduction is due to a large number of free electrons, the electrons in the ntype semiconductor are the majority carriers and holes are the minority carriers. Calculate the electron and hole concentration under steadystate illumination in n type silicon with excess generation rate g l 1016 cm 3s 1, n d 1015 cm 3 and. Assume a compound semiconductor has 25% atomic concentrations of ga, 25% atomic in and 50% atomic of n. Conversely, in a p type semiconductor, holes are majority carriers and electrons are minority carriers. So the electrons will recombine close to the depletion region with the holes. The term p type refers to the positive charge of a hole. However, after 1990, a few semiconductor devices using organic semiconductors and semiconducting polymers have been developed signalling the birth of a futuristic technology of polymerelectronics and molecularelectronics. The majority carrier in an n type semiconductor is the free electron. It is the branch of physics that deals with the emission and effects of electrons emission and. Sheet resistance of a 14 mil thick n type and p type silicon wafer versus doping density.
The term ptype refers to the positive charge of a hole. N d n a, n d n i, electrons n are the majority carriers and holes p are the minority carriers. It is thought that fermi level is located just below the cb bottom and above the vb top for n type and p type semiconducting materials, respectively. Lecture 1 introduction to semiconductors and semiconductor. P type semiconductors are made by doping the pure semiconductor material. That is why we consider holes as majority carriers, and electrons are called minority carriers in a ptype semiconductor.
One that is doped with an acceptor impurity is called a p type semiconductor. N a n d, n a n i, holes p are the majority carriers and electrons n are the minority carriers. In studying p and n type doping, it is natural to ask. Based on my understanding, the p type semiconductor should have electrons as the majority carriers because one electron of the silicon atom in the image above does not bond with the boron atom instead of majority of holes and thus should behave like an n type semiconductor. Each added boron atom creates a deficiency of one electronthat is, a positive hole. In general, the number of majority carriers far exceeds the minority carriers.
The hall effect is the production of a potential difference due to the motion of a conductor through an external magnetic field. Current flow in a p type semiconductor is a little more difficult to explain. Hence, the number of free electrons in a ptype semiconductor is much smaller than the number of holes in it. Such type of impurities which produces ptype semiconductor. Materials, devices and simple circuits semiconductors. Therefore along the junction between the p and n type silicon, a small natural potential is set up between the p and n semiconductor material with negatively charged electrons now on the p type side of the junction, and positively charged holes on the n side of the junction. A large number of holes are provided in the semiconductor material by the addition of trivalent impurities like gallium and indium. A semiconductor that is doped with a donor impurity is called an n type semiconductor. Ptype semiconductor simple english wikipedia, the free.
The hole is the majority charge carrier and the free electron is minority charge carrier such type of semiconductor is called p type semiconductor. If group 3 elements such as such as boron, gallium and indium are added to the semiconductor crystal, the impurity atoms. In this article, you will find the study notes on semiconductors 1 which will cover the topics such as introduction, semiconductor materials, intrinsic and extrinsic semiconductors, properties of semiconductor materials and important terms. Handin assume that an n type semiconductor is uniformly illuminated, producing a uniform excess generation rate g. In 1956, shockley shared the nobel prize in physics for the invention of the transistor with brattain and bardeen fig. It formed by adding trivalent or pentavalent impurity to a pure semiconductor. When the trivalent impurity is added to an intrinsic or pure semiconductor silicon or germanium, then it is said to be an ptype semiconductor. Heres a good rule to remember about rattlesnakes and scorpions. P n type semiconductor a pn junction diode is formed on a single crystal of semiconductor by injecting p type and n type. When wires are connected to the ends, as shown, the device becomes a semiconductor diode.
Fermi level lies near valence band in p type and near conduction. In n type semiconductor electrons are the majority carrier and holes are the minority carrier. Semiconductors doped with acceptors have many holes and few mobile electrons, and are called p type because holes carry positive p charge. We hope this book will be not only a handy source for information on topics in semiconductor physics but also a handbook for looking up material parameters for a wide range of semiconductors. As opposed to ntype semiconductors, ptype semiconductors have a larger hole concentration than electron concentration. Holes appear to move and are spoken of, as if they were particles themselves. If a semiconductor contains both acceptor atoms and donor atoms, the contributed holes and electrons will recombine such that pn ni 2 in equilibrium, and the majority carrier concentration will be determined by the net doping concentration. Calculate the total width of the depletion region if the applied voltage v a equals 0, 0. P type for excess positive charges silicon results if the dopant is boron, which contains one electron fewer than a silicon atom. In this p type semiconductor holes are the majority charge carriers and electrons are the minority charge carriers.
The existence of holes in a doped p type semiconductor is demonstrated by the hall effect. The majority carrier in a p type semiconductor is the hole. Most metal oxides are categorized as n type semiconductors with. Fermi level is a kind of measure of equilibrium electronic energy of a solid material. The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p and ntype dopants. The trivalent impurity used for doping purpose of a ptype semiconductor are boron, gallium, and indium. Calculate the builtin potential of this p n junction. A single semiconductor crystal can have many p and ntype regions. No electric field a p n junction consists of a p type semiconductor next to an n type semiconductor.
When we add trivalent impuritiesboron,aluminium etc to semiconductor materials will create holes. In ptype semiconductors, holes are the majority carriers and electrons are the minority carriers. Why are holes the majority carrier in ptype semiconductor. There once was a very large lake here, the largest lake in texas. The electron in an n type semiconductor is called the majority carrier, whereas the hole in n type semiconductor is termed the minority carrier. Semiconductor doping an overview sciencedirect topics. Under thermal equilibrium conditions, the pn product remains constant, or p. N and p type regions form the cathode and anode respectively operation prior to voltage being applied to the diode, at the junction of the p type and n type regions, free electrons from the n type side move to the p type side and. Crystal as a whole is neutral, but the donor atom becomes an immobile positive ion. Na p ni2n o if na nd, then the semiconductor material is p. Semiconductors types, examples, properties, application. The amount of impurity added is very small compared to the amount of semiconductor. While holes form at the trivalent dopant atom sites, they may move about the semiconductor bar. A p type material is formed by the addition of trivalent impurity atoms to the intrinsic semiconductive material.
The doping of group 3 elements in silicon crystal leads to p type semiconductor. Calculate the potential across the depletion region in the n type semiconductor at 0, 0. Solid state device created by joining the p type and n type material is called as semiconductor diode. Allen institute iit jee main semiconductor class notes pdf. Being bitten by a scorpion or even a rattlesnake is not the worst thing that can happen to you. Out on the lake, rattlesnakes and scorpions find shade under rocks and in the holes dug by the campers. A common p type dopant for silicon is boron or gallium. An n type semiconductor is produced by adding a donor impurity such as as, sb, or p to an intrinsic semiconductor. When a doped semiconductor contains mostly free holes it is called ptype, and when it contains mostly free electrons it is known as ntype. In a ptype semiconductor, the majority carriers are free holes contributed by impurity atoms, and minority carriers are free holes left by the filling of states due to thermal excitation of electrons across the gap. As opposed to n type semiconductors, p type semiconductors have a larger hole concentration than electron concentration. Trivalent impurities such as boron b, gallium g, indium in, aluminiumal etc are called acceptor impurity.