P Type And N Type Materials Pdf

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p type and n type materials pdf

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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. Here we tackle this problem in a relevant class of electron transporting, naphthalene-diimide copolymers, by substituting the imide oxygen with sulfur. This result highlights the effectiveness of chemical tuning to improve air stability of n-type solution-processable polymer conductors and shows a path toward ambient large-area manufacturing of efficient polymer TEGs. Energy harvesting with organics sees its most mature example in organic solar cells, which enable lightweight and large-area solar energy converters suitable for distributed energy generation.

Electrons and “holes’’

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. An electron acceptor dopant is an atom which accepts an electron from the lattice, creating a vacancy where an electron should be called a hole which can move through the crystal like a positively charged particle. An extrinsic semiconductor which has been doped with electron acceptor atoms is called a p-type semiconductor , because the majority of charge carriers in the crystal are positive holes.

In this tutorial, we will learn about an introduction to semiconductors as they are an essential part of Electronics. Before understanding several devices like Semiconductor Diodes, Transistors, etc. This part of the tutorial will lay out a key foundation in easily learning the PN Junction, which is next in line. There are two types of semiconductor components in electronic and electrical circuits. They are active and passive components.

The Doping of Semiconductors

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?

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.

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". It is typical to use B 2 H 6 diborane gas to diffuse boron into the silicon material.


This is called an n-type semiconductor. Boron can also be used to dope a pure crystal of silicon. But since boron only offers 3 of the four electrons that a silicon atom needs, each silicon center is left with a hole. Semiconductors made in this manner are called p-type.


Basics of Semiconductor Diodes

The process of purposefully adding impurities to materials is called doping; semiconductors with impurities are referred to as "doped semiconductors". In a pure intrinsic Si or Ge semiconductor, each nucleus uses its four valence electrons to form four covalent bonds with its neighbors see figure below. Since there are no excess electrons or holes In this case, the number of electrons and holes present at any given time will always be equal. An intrinsic semiconductor. Now, if one of the atoms in the semiconductor lattice is replaced by an element with three valence electrons, such as a Group 3 element like Boron B or Gallium Ga , the electron-hole balance will be changed.

Formation of a PN-Junction

Doping means the introduction of impurities into a semiconductor crystal to the defined modification of conductivity. Other materials are aluminum, indium 3-valent and arsenic, antimony 5-valent.

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Difference Between p Type and n Type Semiconductor

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