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Modulation Doping
Modulation doping is a technique for fabricating semiconductors such that the free charge carriers are spatially separated from the donors. Because this eliminates scattering from the donors, modulation-doped semiconductors have very high carrier mobilities. History Modulation doping was conceived in Bell Labs in 1977 following a conversation between Horst Störmer and Ray Dingle, and implemented shortly afterwards by Arthur Gossard. In 1977, Störmer and Dan Tsui used a modulation-doped wafer to discover the fractional quantum Hall effect. Implementation Modulation-doped semiconductor crystals are commonly grown by epitaxy to allow successive layers of different semiconductor species to be deposited. One common structure uses a layer of AlGaAs deposited over GaAs, with Si n-type donors in the AlGaAs. Applications Field effect transistors Modulation-doped transistors can reach high electrical mobilities and therefore fast operation. A modulation-doped field-effect transistor i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doping (semiconductor)
In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor. Small numbers of dopant atoms can change the ability of a semiconductor to conduct electricity. When on the order of one dopant atom is added per 100 million atoms, the doping is said to be ''low'' or ''light''. When many more dopant atoms are added, on the order of one per ten thousand atoms, the doping is referred to as ''high'' or ''heavy''. This is often shown as ''n+'' for n-type doping or ''p+'' for p-type doping. (''See the article on semiconductors for a more detailed description of the doping mechanism.'') A semiconductor doped to such high levels that it acts more like a conductor than a semiconductor is referred to as a degenerate semiconductor. A semiconductor can be considered i-type semiconductor if it has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Mobility
Electrical mobility is the ability of charged particles (such as electrons or protons) to move through a medium in response to an electric field that is pulling them. The separation of ions according to their mobility in gas phase is called ion mobility spectrometry, in liquid phase it is called electrophoresis. Theory When a charged particle in a gas or liquid is acted upon by a uniform electric field, it will be accelerated until it reaches a constant drift velocity according to the formula : v_\text = \mu E, where : v_\text is the drift velocity ( SI units: m/s), : E is the magnitude of the applied electric field (V/m), : \mu is the mobility (m2/(V·s)). In other words, the electrical mobility of the particle is defined as the ratio of the drift velocity to the magnitude of the electric field: : \mu = \frac. For example, the mobility of the sodium ion (Na+) in water at 25 °C is . This means that a sodium ion in an electric field of 1 V/m would have an averag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell Labs
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by multinational company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several laboratories in the United States and around the world. Researchers working at Bell Laboratories are credited with the development of radio astronomy, the transistor, the laser, the photovoltaic cell, the charge-coupled device (CCD), information theory, the Unix operating system, and the programming languages B, C, C++, S, SNOBOL, AWK, AMPL, and others. Nine Nobel Prizes have been awarded for work completed at Bell Laboratories. Bell Labs had its origin in the complex corporate organization of the Bell System telephone conglomerate. In the late 19th century, the laboratory began as the Western Electric Engineering Department, l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horst Störmer
Horst may refer to: Science * Horst (geology), a raised fault block bounded by normal faults or graben People * Horst (given name) * Horst (surname) * ter Horst, Dutch surname * van der Horst, Dutch surname Places Settlements Germany * Horst, Steinburg, a municipality in the district of Steinburg in Schleswig-Holstein * Horst, Lauenburg, a municipality in the district of Lauenburg in Schleswig-Holstein * Horst, Mecklenburg-Vorpommern, a village and district in the municipality of Sundhagen, Mecklenburg-Vorpommern * , a district in the city of Gelsenkirchen, North Rhine-Westphalia * , a town in the municipality of Seevetal, Lower Saxony Netherlands * Horst aan de Maas, a municipality in the province of Limburg ** Horst, Limburg, the municipal seat of Horst aan de Maas * , a hamlet in the municipality of Ermelo, Gelderland * , a village in the municipality of Gilze en Rijen, North Brabant * Schothorst, , and , districts in the city and municipality of Amersfoort, Utrecht Polan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ray Dingle
Ray may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), a bony or horny spine on a fin Science and mathematics * Ray (geometry), half of a line proceeding from an initial point * Ray (graph theory), an infinite sequence of vertices such that each vertex appears at most once in the sequence and each two consecutive vertices in the sequence are the two endpoints of an edge in the graph * Ray (optics), an idealized narrow beam of light * Ray (quantum theory), an equivalence class of state-vectors representing the same state Arts and entertainment Music * The Rays, an American musical group active in the 1950s * Ray (musician), stage name of Japanese singer Reika Nakayama (born 1990) * Ray J, stage name of singer William Ray Norwood, Jr. (born 1981) * ''Ray'' (Bump of Chicken album) * ''Ray'' (Frazier Chorus album) * ''Ray'' (L'Arc-en-Ciel album) * ''Rays'' (Michael Nesmith album) (former Monkee) * ''Ray'' (soundtrack) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthur Gossard
Arthur C. Gossard was a professor of materials and electrical engineering at the University of California, Santa Barbara. In 1982, he co-discovered the fractional quantum Hall effect. His research is related to molecular beam epitaxy (MBE). He has a doctorate in physics from UC Berkeley. After university, he joined Bell Labs. In 1987, he was elected a member of the US National Academy of Engineering for contributions to the study of the physics of ultra-thin semiconducting layers through molecular beam epitaxy, leading to new physics and new devices. He was also a member of the US National Academy of Sciences. In 2016, Gossard was named as a recipient of a National Medal of Technology and Innovation The National Medal of Technology and Innovation (formerly the National Medal of Technology) is an honor granted by the President of the United States to American inventors and innovators who have made significant contributions to the development .... He died on 26 June 2022. Refer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Daniel C
The Wake are a British post-punk, synth-pop and later indie pop band, formed in Glasgow in 1981 by Gerard "Caesar" McInulty (formerly of Altered Images), Steven Allen (drums) and Joe Donnelly (bass), the latter replaced by Bobby Gillespie. Steven's sister Carolyn Allen also joined on keyboards, and remained in the band thereafter. Gillespie left the band in 1983, replaced by Martin Cunning and then by Alexander 'Mac' Macpherson. History The Wake released their first single on their own Scan 45 label, coupling together "On Our Honeymoon" and "Give Up". This single eventually caught the attention of New Order (band), New Order manager Rob Gretton, who helped the band sign to Factory Records in 1982 and record an LP (''Harmony (The Wake album), Harmony'') at Strawberry Studios in Stockport. This was followed by a number of singles on Factory and its Belgian sister label Factory Benelux. In 1983, The Wake toured with New Order (band), New Order, and thus received critical attention ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fractional Quantum Hall Effect
The fractional quantum Hall effect (FQHE) is a physical phenomenon in which the Hall conductance of 2-dimensional (2D) electrons shows precisely quantized plateaus at fractional values of e^2/h. It is a property of a collective state in which electrons bind magnetic flux lines to make new quasiparticles, and excitations have a fractional elementary charge and possibly also fractional statistics. The 1998 Nobel Prize in Physics was awarded to Robert Laughlin, Horst Störmer, and Daniel Tsui "for their discovery of a new form of quantum fluid with fractionally charged excitations" Laughlin's explanation only applies to fillings \nu = 1/m where m is an odd integer. The microscopic origin of the FQHE is a major research topic in condensed matter physics. Introduction The fractional quantum Hall effect (FQHE) is a collective behavior in a 2D system of electrons. In particular magnetic fields, the electron gas condenses into a remarkable liquid state, which is very delicate, requ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epitaxy
Epitaxy refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epitaxial film or epitaxial layer. The relative orientation(s) of the epitaxial layer to the seed layer is defined in terms of the orientation of the crystal lattice of each material. For most epitaxial growths, the new layer is usually crystalline and each crystallographic domain of the overlayer must have a well-defined orientation relative to the substrate crystal structure. Epitaxy can involve single-crystal structures, although grain-to-grain epitaxy has been observed in granular films. For most technological applications, single domain epitaxy, which is the growth of an overlayer crystal with one well-defined orientation with respect to the substrate crystal, is preferred. Epitaxy can also play an important role while growing superlatti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transistors
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electrical power, power. The transistor is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Some transistors are packaged individually, but many more are found embedded in integrated circuits. Austro-Hungarian physicist Julius Edgar Lilienfeld proposed the concept of a field-effect transistor in 1926, but it was not possible to actually construc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MODFET
A high-electron-mobility transistor (HEMT), also known as heterostructure FET (HFET) or modulation-doped FET (MODFET), is a field-effect transistor incorporating a junction between two materials with different band gaps (i.e. a heterojunction) as the channel instead of a doped region (as is generally the case for a MOSFET). A commonly used material combination is GaAs with AlGaAs, though there is wide variation, dependent on the application of the device. Devices incorporating more indium generally show better high-frequency performance, while in recent years, gallium nitride HEMTs have attracted attention due to their high-power performance. Like other FETs, HEMTs are used in integrated circuits as digital on-off switches. FETs can also be used as amplifiers for large amounts of current using a small voltage as a control signal. Both of these uses are made possible by the FET’s unique current–voltage characteristics. HEMT transistors are able to operate at higher freq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryogenic
In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cryogenic” by accepting a threshold of 120 K (or –153 °C) to distinguish these terms from the conventional refrigeration. This is a logical dividing line, since the normal boiling points of the so-called permanent gases (such as helium, hydrogen, neon, nitrogen, oxygen, and normal air) lie below 120K while the Freon refrigerants, hydrocarbons, and other common refrigerants have boiling points above 120K. The U.S. National Institute of Standards and Technology considers the field of cryogenics as that involving temperatures below -153 Celsius (120K; -243.4 Fahrenheit) Discovery of superconducting materials with critical temperatures significantly above the boiling point of nitrogen has provided new interest in reliable, low cost methods ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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