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A transistor is a semiconductor device used to amplify or switch electrical signals and power. It 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 in miniature form are found embedded in integrated circuits. Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions.
A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material for its function. Its conductivity lies between conductors and insulators. Semiconductor devices have replaced vacuum tubes in most applications. They conduct electric current in the solid state, rather than as free electrons across a vacuum or as free electrons and ions through an ionized gas.
Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure.
Monolithic microwave integrated circuit, or MMIC, is a type of integrated circuit (IC) device that operates at microwave frequencies. These devices typically perform functions such as microwave mixing, power amplification, low-noise amplification, and high-frequency switching. Inputs and outputs on MMIC devices are frequently matched to a characteristic impedance of 50 ohms. This makes them easier to use, as cascading of MMICs does not then require an external matching network. Additionally, most microwave test equipment is designed to operate in a 50-ohm environment.
Wide-bandgap semiconductors are semiconductor materials which have a larger band gap than conventional semiconductors. Conventional semiconductors like silicon and selenium have a bandgap in the range of 0.7 – 1.5 electronvolt (eV), whereas wide-bandgap materials have bandgaps in the range above 2 eV. Generally, wide-bandgap semiconductors have electronic properties which fall in between those of conventional semiconductors and insulators.
Gallium nitride is a binary III/V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronics, high-power and high-frequency devices. For example, GaN is the substrate that makes violet (405 nm) laser diodes possible, without requiring nonlinear optical frequency doubling.
A high-electron-mobility transistor, 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 as the channel instead of a doped region. 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.
Aluminium nitride (AlN) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K) and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.
A heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) that uses different semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle signals of very high frequencies, up to several hundred GHz. It is commonly used in modern ultrafast circuits, mostly radio frequency (RF) systems, and in applications requiring a high power efficiency, such as RF power amplifiers in cellular phones. The idea of employing a heterojunction is as old as the conventional BJT, dating back to a patent from 1951. Detailed theory of heterojunction bipolar transistor was developed by Herbert Kroemer in 1957.
A blue laser emits electromagnetic radiation with a wavelength between 400 and 500 nanometers, which the human eye sees in the visible spectrum as blue or violet.
Indium gallium arsenide (InGaAs) is a ternary alloy of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are group III elements of the periodic table while arsenic is a group V element. Alloys made of these chemical groups are referred to as "III-V" compounds. InGaAs has properties intermediate between those of GaAs and InAs. InGaAs is a room-temperature semiconductor with applications in electronics and photonics.
Aluminium gallium nitride (AlGaN) is a semiconductor material. It is any alloy of aluminium nitride and gallium nitride.
Gallium(III) oxide is an inorganic compound and ultra-wide-bandgap semiconductor with the formula Ga2O3. It is actively studied for applications in power electronics, phosphors, and gas sensing. The compound has several polymorphs, of which the monoclinic β-phase is the most stable. The β-phase’s bandgap of 4.7–4.9 eV and large-area, native substrates make it a promising competitor to GaN and SiC-based power electronics applications and solar-blind UV photodetectors. The orthorhombic ĸ-Ga2O3 is the second most stable polymorph. The ĸ-phase has shown instability of subsurface doping density under thermal exposure. Ga2O3 exhibits reduced thermal conductivity and electron mobility by an order of magnitude compared to GaN and SiC, but is predicted to be significantly more cost-effective due to being the only wide-bandgap material capable of being grown from melt. β-Ga2O3 is thought to be radiation-hard, which makes it promising for military and space applications.
The field-effect transistor (FET) is a type of transistor that uses an electric field to control the current through a semiconductor. It comes in two types: junction FET (JFET) and metal-oxide-semiconductor FET (MOSFET). FETs have three terminals: source, gate, and drain. FETs control the current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and source.
Indium aluminium nitride (InAlN) is a direct bandgap semiconductor material used in the manufacture of electronic and photonic devices. It is part of the III-V group of semiconductors, being an alloy of indium nitride and aluminium nitride, and is closely related to the more widely used gallium nitride. It is of special interest in applications requiring good stability and reliability, owing to its large direct bandgap and ability to maintain operation at temperatures of up to 1000 °C., making it of particular interest to areas such as the space industry. InAlN high-electron-mobility transistors (HEMTs) are attractive candidates for such applications owing to the ability of InAlN to lattice-match to gallium nitride, eliminating a reported failure route in the closely related aluminium gallium nitride HEMTs.
Aristos Christou is an American engineer and scientist, academic professor and researcher. He is a Professor of Materials Science, Professor of Mechanical Engineering and Professor of Reliability Engineering at the University of Maryland.
Srabanti Chowdhury is an Indian American Electrical Engineer who is an associate professor of electrical engineering at Stanford University. She is a senior fellow of the Precourt Institute for Energy. At Stanford she works on ultra-wide and wide-bandgap semiconductors and device engineering for energy-efficient electronic devices. She serves as Director for Science Collaborations at the United States Department of Energy Energy Frontier Research Center ULTRA.
Tomás A. Palacios Gutiérrez is a Spanish–American Electrical & Microelectronics Engineer known for his work in advanced device and material design. He holds the chair Clarence J. LeBel Professor of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology and director of Microsystems Technology Laboratories (MTL). Palacios is known for inventing a super-thin 'sheet' that can charge mobile phones with out electricity.
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. Epitaxial growth and semiconductor device fabrication are technologies used to develop stacked crystalline layers of different materials with specific semiconductor properties on a crystalline substrate, commonly silicon or silicon carbide (SiC) materials, to achieve the desired performance of the microelectronic devices, such as transistors and diodes. The crystal structure of these layers is with high density of imperfections, such as dislocations and stacking faults. Therefore the microelectronic engineers and technologists have developed different techniques to eliminate or minimize the density of these structural defects in order to improve the microelectronic devices operation. One such approach is Selective Area Growth technology.
The first Light-Emitting Diode (LED) was created in 1927 by Russian inventor Oleg Losev, and used silicon carbide as a semiconductor. However, electroluminescence as a phenomenon was discovered twenty years earlier by the English experimenter Henry Joseph Round of Marconi Labs, using the same crystal and a cat's-whisker detector. Despite having distributed his report in Soviet, German and British scientific journals, Losev's LED found no practical use for several decades, partly due to the very inefficient light-producing properties of the semiconductor used.
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