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P Type And N Type Materials Pdf

p type and n type materials pdf

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Electrons and “holes’’

Semiconductors are materials that have properties of both normal conductors and insulators. Semiconductors fall into two broad categories:. In the classic crystalline semiconductors, electrons can have energies only within certain bands ranges of energy levels. The energy of these bands is between the energy of the ground state and the free electron energy the energy required for an electron to escape entirely from the material. The energy bands correspond to a large number of discrete quantum states of the electrons. Most of the states with low energy closer to the nucleus are occupied, up to a particular band called the valence band. Semiconductors and insulators are distinguished from metals by the population of electrons in each band.

Basics of Semiconductor Diodes

P-n junctions are formed by joining n -type and p -type semiconductor materials, as shown below. Since the n -type region has a high electron concentration and the p -type a high hole concentration, electrons diffuse from the n -type side to the p -type side. Similarly, holes flow by diffusion from the p -type side to the n -type side. If the electrons and holes were not charged, this diffusion process would continue until the concentration of electrons and holes on the two sides were the same, as happens if two gasses come into contact with each other. However, in a p-n junction, when the electrons and holes move to the other side of the junction, they leave behind exposed charges on dopant atom sites, which are fixed in the crystal lattice and are unable to move. On the n -type side, positive ion cores are exposed. On the p -type side, negative ion cores are exposed.

An extrinsic semiconductor is one that has been doped ; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal, which is called an intrinsic semiconductor. In an extrinsic semiconductor it is these foreign dopant atoms in the crystal lattice that mainly provide the charge carriers which carry electric current through the crystal. The doping agents used are of two types, resulting in two types of extrinsic semiconductor. An electron donor dopant is an atom which, when incorporated in the crystal, releases a mobile conduction electron into the crystal lattice. An extrinsic semiconductor which has been doped with electron donor atoms is called an n-type semiconductor , because the majority of charge carriers in the crystal are negative electrons.

Pure semiconductors are relatively good insulators as compared with metals, though not nearly as good as a true insulator like glass. To be useful in semiconductor applications, the intrinsic semiconductor pure undoped semiconductor must have no more than one impurity atom in 10 billion semiconductor atoms. This is analogous to a grain of salt impurity in a railroad boxcar of sugar. Impure, or dirty semiconductors are considerably more conductive, though not as good as metals. Why might this be? To answer that question, we must look at the electron structure of such materials in Figure below.

p type and n type materials pdf

I. P-Type, N-Type Semiconductors

Extrinsic semiconductor

The various factors like doping element, nature of doping element, the majority and minority carriers in the p-type and n-type semiconductor. The density of electrons and holes, energy level and Fermi level, the direction of movement of majority carriers, etc. The difference between a p-type semiconductor and an n-type semiconductor is given below in the tabulated form. The p-type semiconductor is formed when the Trivalent impurity is added to the pure semiconductor. Similarly, when a Pentavalent impurity is added to the pure semiconductor n-type semiconductor is obtained. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.

The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties, producing n-type and p-type semiconductors. Pentavalent impurities Impurity atoms with 5 valence electrons produce n-type semiconductors by contributing extra electrons. Trivalent impurities Impurity atoms with 3 valence electrons produce p-type semiconductors by producing a " hole " or electron deficiency. The addition of pentavalent impurities such as antimony, arsenic or phosphorus contributes free electrons, greatly increasing the conductivity of the intrinsic semiconductor. Phosphorus may be added by diffusion of phosphine gas PH3. The addition of trivalent impurities such as boron, aluminum or gallium to an intrinsic semiconductor creates deficiencies of valence electrons, called "holes".

Он вылетел из-за поворота на уровне лодыжек подобно рапире фехтовальщика. Халохот попробовал отклониться влево, но не успел и со всей силы ударился об него голенью. В попытке сохранить равновесие он резко выбросил руки в стороны, но они ухватились за пустоту. Внезапно он взвился в воздух и боком полетел вниз, прямо над Беккером, распростертым на животе с вытянутыми вперед руками, продолжавшими сжимать подсвечник, об который споткнулся Халохот. Халохот ударился сначала о внешнюю стену и только затем о ступени, после чего, кувыркаясь, полетел головой. Пистолет выпал из его рук и звонко ударился о камень.


Джабба встряхнул бутылочку с острой приправой Доктор Пеппер. - Выкладывай. - Может быть, все это чепуха, - сказала Мидж, - но в статистических данных по шифровалке вдруг вылезло что-то несуразное. Я надеюсь, что ты мне все объяснишь. - В чем же проблема? - Джабба сделал глоток своей жгучей приправы. - Передо мной лежит отчет, из которого следует, что ТРАНСТЕКСТ бьется над каким-то файлом уже восемнадцать часов и до сих пор не вскрыл шифр.


  1. Dagoberto Y.

    09.12.2020 at 19:11

    Organic thermoelectrics are attractive for the fabrication of flexible and cost-effective thermoelectric generators TEGs for waste heat recovery, in particular by exploiting large-area printing of polymer conductors.

  2. Kenneth R.

    12.12.2020 at 03:53

    In this tutorial, we will learn about an introduction to semiconductors as they are an essential part of Electronics.

  3. Priscilla C.

    12.12.2020 at 20:29

    Doping means the introduction of impurities into a semiconductor crystal to the defined modification of conductivity.

  4. Sillekapho

    17.12.2020 at 02:28

    The process of purposefully adding impurities to materials is called doping; semiconductors with impurities are referred to as "doped semiconductors".

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