Contrast this with resistivity, which has units of m. Ntype semiconductor simple english wikipedia, the free. Hall coe cient is a parameter that measures the magnitude of the hall e ect in the sample. This unique property makes it an excellent material to conduct electricity in a controlled. What is the hole concentration in an n type semiconductor with 1015 cm3 of donors. A semiconductor diode devices that allow current in only one direction consists of p type and n type semiconductors placed in junction with one another. An intrinsic semiconductor is an undoped material with an. Doped semiconductors n type materials p type materials diodes and transistors. Increase nd until carrier tunneling is possible ec ev ef ef efe efh ev ec efh ev efe ec ohmic contact to n type semiconductor ohmic contact to p type semiconductor cite as. Intrinsic semiconductor and extrinsic semiconductor. The difference between a p type semiconductor and n type semiconductor are given below in tabulated form.
The p type semiconductor has a larger hole concentration, which results in the positive charge. Extrinsic semiconductor is formed by adding a small amount of impurity. The n type semiconductors are doped with pentavalent impurities. An n type semiconductor is produced by adding a donor impurity such as as, sb, or p to an intrinsic semiconductor. The new element either introduces donor atoms or acceptor atoms. In most cases, the doping of a semiconductor leads either to the creation of donor or acceptor levels ntype ptype semiconductors.
Current flow in semiconductors university of north. Depending upon the type of impurity atoms added, an extrinsic semiconductor can be classified as n type or p type. A unique feature of the semiconductors is that they are bipolar in nature and in them, the current is transported by the electrons and holes. Based on the dopants used the extrinsic semiconductors are further classified as n type semiconductor and p type semiconductor. Solid we know that, each substance is composed of atoms. The p type and n type are two different types of semiconductors. By introducing group v elements like phosphorous into silicon, extra valence electrons. Once a positive potential is applied to the n type semiconductor, the remaining free electrons form a drift to produce an electrical current. Where n v is the effective density of states in the valence band.
A semiconductor that is doped with a donor impurity is called an n type semiconductor. A semiconductor like silicon has a band gap that is large enough that thermal excitations of electrons from the. Classification of substances on the basis of conduction of electricity. As per theory of semiconductor, impure semiconductors are called extrinsic semiconductors. A pnjunction is formed when an n type material is fused together with a p type material creating a semiconductor diode. The conduction in the ntype semiconductor is because of the free electrons denoted by the pentavalent impurity atoms. But since boron only offers 3 of the four electrons that a silicon. Although currents may be induced in pure, or intrinsic, semiconductor crystal due to the. The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p and n type dopants. The silicon is known as n type and the dopants are called acceptors. The 5th electron finds no place in the covalent bonding so becomes free. They are mainly classified into two types as follows. The silicon becomes an n type semiconductor because of the addition of the electron. The formation of a p n semiconductor junction is described and its conduction properties are discussed.
However, in an n type semiconductor, the density of states increases, therefore, accommodating more electrons at higher energy levels. Physics notes class 12 chapter 14 semiconductor electronics, materials, devices and sample circuits it is the branch of science which deals with the electron flow through a vacuum, gas or semiconductor. To explain the formation of n type semiconductor, let us introduce a pentavalent impurity atom into the lattice of pure silicon crystal. The fermi level for p type semiconductor is given as. The charges depend on the hole concentration and the electron concentration. In this chapter, we will restrict ourselves to the study of inorganic semiconductors, particularly. A third reason is the fact that there are very few candidate shallow. Fifth electron is superfluous, becomes free electron and enters into conduction band.
The p type carries a positive charge, while the n type carries a negative charge. Silicon is the primary semiconductor used in vlsi systems. N type semiconductors are created on doping a semiconductor by exposing them to other elements. Semiconductors types, examples, properties, application. Type or ptype semiconductor depending on the type of dopant. Mobile charge carriers in semiconductors crystal structures, bonding mobile holes and electrons dopants and doping silicon in thermal equilibrium generationrecombination. So the hall voltage produced in the n type semiconductor is negative. It is made by adding an impurity to a pure semiconductor such as silicon or germanium. In the previous tutorial we saw how to make an n type semiconductor material by doping a silicon atom with small amounts of antimony and also how to make a p type semiconductor material by doping another silicon atom with boron. 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 junction of a p type and n type semiconductor forms a depletion region where current conduction is reserved by the lack of mobile charge carriers.
Ptype semiconductor simple english wikipedia, the free. In 100 million parts of semiconductor one part of impurity is added. Created when the dopant is an element that has five electrons in its valence layer. An n type semiconductor is a better conductor than the intrinsic semiconductor material. Extrinsic semiconductors are components of many common electrical devices. Temperature dependence of semiconductor conductivity. Therefore, the fermi level in the p type semiconductor lies close to the valence band. Semiconductor and simple circuitsnot to be republished. A n type semiconductor is defined as a type of extrinsic semiconductor doped with a pentavalent impurity element which has five electrons in its valence shell. Pure tetravalent substance is known as intrinsic semiconductoe and some impurity is mixed with that pure substance, it. Semiconductors can conduct electricity under preferable conditions or circumstances. A single semiconductor crystal can have many p and n type regions. N and p type semiconductors neither pure siliconsi nor germaniumge are great conductors. For n type semiconductor, the law of mass relation can be written as n n 1 for p type semiconductor, the law of mass relation can be written as l l 2 from equations 1 and 2 we observe that, the product of majority and minority charge carrier concentration at a particular temperature is equal to the square of intrinsic carrier.
Ntype semiconductors are a type of extrinsic semiconductor where the dopant atoms are capable of providing extra conduction electrons to the host material e. Semiconductor type intrinsic extrinsic ptype ntype. N type semiconductor 1 n type semiconductor n type semiconductors are a type of extrinsic semiconductor where the dopant atoms are capable of providing extra conduction electrons to the host material e. Semiconductor doping an overview sciencedirect topics. As a result, the potential difference is developed between the upper and bottom surface of the n type semiconductor. An ntype semiconductor is a type of material used in electronics. Trivalent impurities such as boron b, gallium ga, indiumin, aluminiumal etc are called acceptor impurity. In our article on semiconductors, we discussed that semiconductors are amorphous or crystalline solids that have a conductivity between that of a conductor and an insulator, either due to the presence of an impurity extrinsic semiconductors or because of temperature change. Similarly, the n type has a larger electron concentration. Because of the large number of donor electrons, there are. Other semiconductors organic semiconductors semiconductor like properties are also found in organic compounds like polydiacetylene ch2 n with conjugate carbon chains, fullerenes, nanotubes, bn nanotubes, etc. The resultant material is known as an ntype semiconductor. The impurities used may be phosphorus, arsenic, antimony, bismuth or some other.
The density of electrons and holes, energy level and fermi level, the direction of movement of majority carriers, etc. V q p n n p p p 1 where n and p refer to the mobilities of the electrons and holes, and n and p refer to the density of electrons and holes. The semiconductors have the conductivity which is between the conductors and the insulators. These electrons are the excess free electrons with. Applications of semiconducting materials karen porter. Similarly, part c of the figure shows that, if an atom with three outer electrons, such as boron, is substituted for a silicon atom, an additional electron is accepted to form four covalent bonds around the boron atom, and a. Ptype, ntype semiconductors and pn junction concept for. A semiconductor diode is a device typically made up of a single p n junction. Currently, most semiconductor diodes use doped silicon or germanium. When the trivalent impurity is added to an intrinsic or pure semiconductor silicon or germanium, then it is said to be an p type semiconductor. Difference between p type and n type semiconductor. Boron can also be used to dope a pure crystal of silicon.
One that is doped with an acceptor impurity is called a p type semiconductor. Organic molecules can easily be tailored at the molecular level and tuned for applications. The phosphorus atoms join right in the crystal structure of the silicon, each one bonding with four adjacent silicon atoms just like a silicon atom would. Two separate bits of semiconductor, one is an n type, the other is a p type ef 2. Semiconductors ppt and pdf report free study mafia. An n type semiconductor is a type of material used in electronics it is made by adding an impurity to a pure semiconductor such as silicon or germanium. Junction comes into the equilibrium by balancing the fermi level. They form a crystal lattice by having each atom share all of its 4 valence electrons with neighbouring atoms. The pentavalent elements are called so as they have 5 electrons in their valence shell. Extrinsic semiconductor is of two types p type and n type semiconductor. The majority charge carriers in n type semiconductors are electrons and minority charge carriers are holes. Metalsemiconductor ohmic contacts stanford university. The pentavalent atom has 5 valance electrons, but only 4 form covalent bonds with the neighbouring atoms. N type semiconductors have a large number of donors, dopant atoms that donate electrons to the conduction band.
The pentavalent impurity or dopant elements are added. An extrinsic semiconductor is one in which an impurity with a valency higher or lower than the valency of the pure semi conductoris added, so as to increase the electrical conductivity of the semiconductor. Semiconductors, diodes, transistors horst wahl, quarknet presentation, june 2001 electrical conductivity. Ptype, ntype semiconductors engineering libretexts. Depending on the type of impurity added we have two types of semiconductors. In the n type semiconductor, the electric field is primarily produced due to the negatively charged free electrons. Another reason is that the defects, which we now know are not responsible for n type conductivity, do play a role as compensating centers in p type doping 20,22,26,27. Holeelectron pairs are continually formed by thermal agitation of the lattice in an ntype semiconductor. This type of semiconductor is obtained when a pentavalent material like antimonty. The junctions which formed where n type and p type semiconductors are joined together is called p n junction.