In this tutorial, we will learn about an introduction to semiconductors as they are an essential part of Electronics.
Electrical Type of the elements
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. Diodes are the foremost active components and resistors are the foremost passive components in electronic design circuits.
Diodes are essentially unidirectional devices having exponential relationship for the current-voltage characteristics are made from semiconductor materials. The three necessary materials that are utilized in electronics are insulators, semiconductors and conductors. These materials are classified in terms of electrical phenomenon. Electrical resistivity conjointly known as electrical resistance is a measure of how efficiently a material refuses the electrical current to flow through it. A material with low electrical resistivity indicates the effective movement of electrical charge throughout the semiconductor.
Semiconductors are the materials whose resistivity values are in between insulators and conductors. These materials are neither smart insulators nor smart conductors. Samples of semiconductors are silicon and germanium. Semiconductors have high importance in the manufacture of electronic circuits and integrated devices. The conductivity of semiconductors can be altered easily by varying the temperature and concentration of doping in the fabrication process.
The capability to conduct electricity in semiconductor materials is considerably increased by a adding definite quantity of impurities to the crystalline lattice producing additional free electrons than holes. The properties of semiconductor materials change considerably by adding small amounts of impurities to it. The process of shifting the balance between electrons and holes by incorporating impurity atoms in the silicon crystal lattice is called as doping. These impurity atoms are known as dopants.
Based on the type of doping material incorporated, semiconductor crystals are classified into two types particularly n-type semiconductors and p-type semiconductors. Group —V elements such as phosphorus, antimony and arsenic are usually classified as N-type impurities.
These elements have five valence electrons. When N-type impurities are doped into silicon crystal, four of the five valence electrons form four strong covalent bonds with adjacent crystal atoms leaving one free electron. Likewise, every N-type impurity atom produces a free electron in the conduction band which will drift to conduct electric current if a potential is applied to the material.
N-type semiconductors can also be referred as Donors. Group—III elements such as boron, aluminium, gallium and indium are usually classified as P-type impurities. These elements have three valence electrons.One reason the periodic table of the elements is so useful is that it is a means of arranging elements according to their similar properties. This is what is meant by periodicity or periodic table trends. There are multiple ways of grouping the elements, but they are commonly divided into metals, semimetals metalloidsand nonmetals.
You'll find more specific groups, like transition metals, rare earthsalkali metals, alkaline earth, halogens, and noble gasses. Click on an element to read about the chemical and physical properties of the group to which that element belongs. The lanthanides rare earth and actinides are also transition metals.
While there are radioisotopes of other elements, all of the actinides are radioactive. The noble gasses have complete valence electron shells, so they act differently. Unlike other groups, noble gasses are unreactive and have very low electronegativity or electron affinity. Share Flipboard Email.
Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter.
Updated April 01, Less dense than other metals One loosely bound valence electron Highly reactive, with reactivity increasing moving down the group The largest atomic radius of elements in their period Low ionization energy Low electronegativity.
Two electrons in the valence shell Readily form divalent cations Low electron affinity Low electronegativity. Very hard, usually shiny, ductile, and malleable High melting and boiling points High thermal and electrical conductivity Form cations positive oxidation states Tend to exhibit more than one oxidation state Low ionization energy.
Electronegativity and ionization energy intermediate between that of metals and nonmetals May possess a metallic luster Variable density, hardness, conductivity, and other properties Often make good semiconductors Reactivity depends on the nature of other elements in the reaction. The halogens and noble gases are nonmetals, although they have their own groups, too.
High ionization energy High electronegativity Poor electrical and thermal conductors Form brittle solids Little if any metallic luster Readily gain electrons. Extremely high electronegativity Very reactive Seven valence electrons, so elements from this group typically exhibit a -1 oxidation state.
Electrical properties can be indicated by resistivity. Conductors such as gold, silver and copper have low resistance and conduct electricity easily. Insulators such as rubber, glass and ceramics have high resistance and are difficult for electricity to pass through. Semiconductors have properties somewhere between these two. Their resistivity might change according to the temperature for example.
At a low temperature, almost no electricity passes through them. But when the temperature rises, electricity passes through them easily. Semiconductors containing almost no impurities conduct almost no electricity.
But when some elements are added to the semiconductorselectricity passes through them easily. Semiconductors comprising a single element are called elemental semiconductorsincluding the famous semiconductor material Silicon. On the other hand, semiconductors made up of two or more compounds are called compound semiconductorsand are used in semiconductor lasers, light-emitting diodesetc.
An atom is consisting of a nucleus and electrons orbiting the nucleus. The electrons cannot orbit the nucleus at any distance in the atomic space surrounding the nucleus, but only certain, very specific orbits are allowed, and only exist in specific discrete levels. These energies are called energy levels. A large number of atoms gather to form a crystal, and interacts in a solid material, then the energy levels became so closely spaced that they form bands. This is the energy band. Metals, semiconductors and insulators are distinguished from each others by their band structures.
Their band structures are shown in the figure below. This means that the metal always has electrons that can move freely and so can always carry current.
Such electrons are known as free electrons. These free electrons are responsible for current that flows through a metal. To get to the conduction band, the electron has to gain enough energy to jump the band gap. Once this is done, it can conduct. In semiconductors at room temperature, the band gap is smaller, there is enough thermal energy to allow electrons to jump the gap fairly easily and make the transitions in conduction band, given the semiconductor limited conductivity.Semiconductors, Insulators \u0026 Conductors, Basic Introduction, N type vs P type Semiconductor
At low temperature, no electron possesses sufficient energy to occupy the conduction band and thus no movement of charge is possible.
At absolute zero, semiconductors are perfect insulators, The density of electrons in conduction band at room temperature is not as high as in metals, thus cannot conduct current as good as metal.
The electrical conductivity of semiconductor is not as high as metal but also not as poor as electrical insulator. That is why, this type of material is called semiconductor - means half conductor. The band gap for insulators is large so very few electrons can jump the gap.Semiconductorany of a class of crystalline solids intermediate in electrical conductivity between a conductor and an insulator. Semiconductors are employed in the manufacture of various kinds of electronic devices, including diodestransistorsand integrated circuits.
Such devices have found wide application because of their compactness, reliability, power efficiencyand low cost. As discrete components, they have found use in power devices, optical sensors, and light emitters, including solid-state lasers. They have a wide range of current- and voltage-handling capabilities and, more important, lend themselves to integration into complex but readily manufacturable microelectronic circuits. They are, and will be in the foreseeable future, the key elements for the majority of electronic systems, serving communications, signal processing, computing, and control applications in both the consumer and industrial markets.
Solid-state materials are commonly grouped into three classes: insulators, semiconductors, and conductors. At low temperatures some conductors, semiconductors, and insulators may become superconductors. The conductivities of semiconductors are between these extremes and are generally sensitive to temperature, illumination, magnetic fields, and minute amounts of impurity atoms.
For example, the addition of about 10 atoms of boron known as a dopant per million atoms of silicon can increase its electrical conductivity a thousandfold partially accounting for the wide variability shown in the preceding figure. The study of semiconductor materials began in the early 19th century. The elemental semiconductors are those composed of single species of atoms, such as silicon Sigermanium Geand tin Sn in column IV and selenium Se and tellurium Te in column VI of the periodic table.
There are, however, numerous compound semiconductors, which are composed of two or more elements. Pure silicon is the most important material for integrated circuit applications, and III-V binary and ternary compounds are most significant for light emission.
Prior to the invention of the bipolar transistor insemiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. During the early s germanium was the major semiconductor material.
However, it proved unsuitable for many applications, because devices made of the material exhibited high leakage currents at only moderately elevated temperatures. Since the early s silicon has become by far the most widely used semiconductor, virtually supplanting germanium as a material for device fabrication. The main reasons for this are twofold: 1 silicon devices exhibit much lower leakage currents, and 2 silicon dioxide SiO 2which is a high-quality insulator, is easy to incorporate as part of a silicon-based device.
Thus, silicon technology has become very advanced and pervasivewith silicon devices constituting more than 95 percent of all semiconductor products sold worldwide.If an abrupt change in impurity type from acceptors p -type to donors n -type occurs within a single crystal structure, a p - n junction is formed see parts B and C of the figure.
On the p side, the holes constitute the dominant carriers and so are called majority carriers. A few thermally generated electrons will also exist in the p side; these are termed minority carriers. On the n side, the electrons are the majority carriers, while the holes are the minority carriers. Near the junction is a region having no free charge carriers. This region, called the depletion layer, behaves as an insulator. The most important characteristic of p - n junctions is that they rectify.
Part A of the figure shows the current-voltage characteristics of a typical silicon p - n junction. When a forward bias is applied to the p - n junction i. However, when a reverse bias is applied as in part C of the figurethe charge carriers introduced by the impurities move in opposite directions away from the junction, and only a small leakage current flows.
As the reverse bias is increased, the leakage current remains very small until a critical voltage is reached, at which point the current suddenly increases. This sudden increase in current is referred to as the junction breakdown, usually a nondestructive phenomenon if the resulting power dissipation is limited to a safe value.
The applied forward voltage is typically less than one volt, but the reverse critical voltage, called the breakdown voltage, can vary from less than one volt to many thousands of volts, depending on the impurity concentration of the junction and other device parameters. Although other junction types have been invented including p - n - p and n - p - np - n junctions remain fundamental to semiconductor devices. For further details on applications of these basic semiconductor properties, see transistor and integrated circuit.
Article Media. Info Print Print. Table Of Contents. Submit Feedback. Thank you for your feedback. Introduction Semiconductor materials Electronic properties The p - n junction. Load Previous Page. The p - n junction If an abrupt change in impurity type from acceptors p -type to donors n -type occurs within a single crystal structure, a p - n junction is formed see parts B and C of the figure.
Learn More in these related Britannica articles:.
Materials are classified as conductors, insulators, or semiconductors according to their electric conductivity. The classifications can be understood in atomic terms.
Electrons in an atom can have only certain well-defined energies,…. Semiconductor s have conducting properties intermediate to those of insulators and metals. In some cases the semiconductors are insulators, while in others they are metals. Semiconductor s share with insulators the property that they have no conduction electrons in a perfect crystal without thermal fluctuations.Between the metals and nonmetals is a group of elements known as either the semimetals or the metalloidswhich are elements that have properties intermediate between those of the metals and nonmetals.
Most metalloids have a shiny, metallic appearance but are brittle, unexceptional electrical conductors and display nonmetallic chemical properties. Metalloids have semiconductor properties and form amphoteric oxides. Because these elements have intermediate properties, it's sort of a judgment call as to whether a particular element is a metalloid or should be assigned to one of the other groups. You'll find metalloids are classified differently in different classification systems, depending on the scientist or author.
There is no single "right" way to divide the elements. Elementtennessinehas not been produced in sufficient amounts to verify its properties but is predicted to be a metalloid. Some scientists consider neighboring elements on the periodic table to either be metalloids or to have metalloid characteristics.
An example is carbon, which may be considered either a nonmetal or a metalloid, depending on its allotrope. The diamond form of carbon looks and behaves as a nonmetal, while the graphite allotrope has a metallic luster and acts as an electrical semiconductor and so is a metalloid. Phosphorus and oxygen are other elements that have both nonmetallic and metalloid allotropes.
Selenium is considered to be a metalloid in environmental chemistry. Other elements that may behave as metalloids under certain conditions are hydrogen, nitrogen, sulfur, tin, bismuth, zinc, gallium, iodine, lead, and radon.
Basics of Semiconductor Diodes
The electronegativities and ionization energies of the metalloids are between those of the metals and nonmetals, so the metalloids exhibit characteristics of both classes. Silicon, for example, possesses a metallic luster, yet it is an inefficient conductor and is brittle.
The reactivity of the metalloids depends on the element with which they are reacting. For example, boron acts as a nonmetal when reacting with sodium yet as a metal when reacting with fluorine. The boiling points, melting points, and densities of the metalloids vary widely. The intermediate conductivity of metalloids means they tend to make good semiconductors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels.
Facebook Facebook Twitter Twitter. Updated September 14, What type of elements of the periodic table are semiconductors? Section from the periodic table. More common semiconductor materials are shown in blue.
A semiconductor can be either of a single element, such as Si or Ge, a compoundsuch as GaAsInP or CdTeor an alloy, such as Si x Ge 1 - x or Al x Ga 1 - x As, where x is the fraction of the particular element and ranges from 0 to 1. See Full Answer. Which type of elements are used as semiconductors? Although some pure elements and many compounds display semiconductor properties, silicongermaniumand compounds of gallium are the most widely used in electronic devices.
Elements near the so-called " metalloid staircase", where the metalloids are located on the periodic table, are usually used as semiconductors. Because semiconductors have a unique atomic structure that allows their conductivity to be controlled by stimulation with electric currents, electromagnetic fields, or even light. In a process called doping, phosphorus or arsenic atoms are mixed into the silicon.
The term n-type comes from the negative charge of the electron. In n-type semiconductorselectrons are the majority carriers and holes are the minority carriers. N-type semiconductors are created by doping an intrinsic semiconductor with donor impurities.
A common dopant for n-type silicon is phosphorus or arsenic. What is the most common element in a semiconductor? Semiconductor materials. The most commonly used semiconductor material is Silicon. Used for thousands of years to make ordinary glass, Silicon is a very common element.
Silicon turns up in lots of rocks and forms the sand on beaches. What materials are used to make semiconductors?
Semiconductor materials list. What is a semiconductor element? Semiconductors : The conductivity of those elements with four valence electrons in the carbon group is not as good as the conductors but still better than the insulators, and they are given the name semiconductors.