what is mean by semiconductor?
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A substance as germanium or silicon whose electrical conductivity is intermediate between that of a metal and an insulator.
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Photonics like electronics is the manipulation of photons or light waves to carry info. Micro photonics is the application of photonic principles on a micro level eg. photonic chips.
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PNP: Semiconductor crystal structure consisting of an N-type region sandwiched between two P-type regions, as commonly used in bipolar transistors\nwhereas\nNPN transistor: A transistor which has a base of P-type silicon sandwiched between an emitter and a collector of N-type silicon.
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A solar cell (or a "photovoltaic" cell) is a semiconductor device that converts photons from the sun (solar light) into electricity. In general a solar cell that includes both solar and non-solar sources of light (such as photons from incandescent bulbs) is termed a photovoltaic cell. Fundamentally, the device needs to fulfill only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity. This conversion is called the photovoltaic effect, and the field of research related to solar cells is known as photovoltaics.\n\nSolar cells have many applications. Historically solar cells have been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth orbiting satellites, consumer systems, e.g. handheld calculators or wrist watches, remote radiotelephones and water pumping applications. Recently solar cells are particularly used in assemblies of solar modules (photovoltaic arrays) connected to the electricity grid through an inverter, often in combination with a net metering arrangement.\n\nSolar cells are regarded as one of the key technologies towards a sustainable energy supply.\n\n\n\n\n\n\nThree generations of development\n\n[edit] First\nThe first generation photovoltaic, consists of a large-area, single layer p-n junction diode, which is capable of generating usable electrical energy from light sources with the wavelengths of solar light. These cells are typically made using silicon wafer. First generation photovoltaic cells (also known as silicon wafer-based solar cells) are the dominant technology in the commercial production of solar cells, accounting for more than 86% of the solar cell market.\n\n\n[edit] Second\nThe second generation of photovoltaic materials is based on the use of thin-film deposits of semiconductors. These devices were initially designed to be high-efficiency, multiple junction photovoltaic cells. Later, the advantage of using a thin-film of material was noted, reducing the mass of material required for cell design. This contributed to a prediction of greatly reduced costs for thin film solar cells. However, most of the assembly costs for depositing thin film solar cells are still significantly higher than for bulk silicon technologies. Another advantage of the reduced mass is that less support is needed when placing panels on rooftops and it allows fitting panels on light materials, even textiles.\n\n\n[edit] Third\nThird generation photovoltaics are very different from the other two, broadly defined as semiconductor devices which do not rely on a traditional p-n junction to separate photogenerated charge carriers. These new devices include photoelectrochemical cells, Polymer solar cells, and nanocrystal solar cells.\n\n\n[edit] History\nMain article: Timeline of solar cells\nThe term "photovoltaic" comes from the Greek φώς:phos meaning "light", and the name of the Italian physicist Volta, after whom the volt (and consequently voltage) are named. It means literally of light and electricity.\n\nThe photovoltaic effect was first recognised in 1839 by French physicist Alexandre-Edmond Becquerel. However it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. Russell Ohl patented the modern solar cell in 1946 (US2402662, "Light sensitive device"). Sven Ason Berglund had a prior patent concerning methods of increasing the capacity of photosensitive cells. The modern age of solar power technology arrived in 1954 when Bell Laboratories, experimenting with semiconductors, accidentally found that silicon doped with certain impurities was very sensitive to light.\n\nThis resulted in the production of the first practi
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A thyristor?\n\nIts a 4-layer semiconductor device that works as an avalanche switch.  It can be triggered into conduction any time but must wait for zero current to turn off.
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solid\nliquid\ngas\nplasma
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Silicon diodes - general purpose: rectifiers, clampers, etc\nGermanium diodes - low voltage drop\nSchottky diodes - fast switching\nTunnel diodes - fast switching, oscillators\nZener diodes - voltage regulators\nLight Emitting diodes (LED) - displays
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Hi,\n\nIt stands for metal oxide semiconductor field effect transistors. In the pass, people use metal material (aluminum) as the gate and oxide as insulator. That's why it is called metal-oxide. And it uses semiconductor to achieve the on/off function or amplification operations through the electric field. That's use it is called field effect transistors. Transistors means "trans-resistors (means changing resistance)". \n\n\nIn summary, by applying voltage to the metal gate, through the oxide insulator, we can achieve "trans-resistor" effect in the semiconductor due to the electric field. That's why we have MOSFET - Metal-oxide-semiconductor field effect transistors.\n\nBut today, people are using poly-silicon as the gate material. But we continue to name it as MOSFET.\n\nLet us know if you have more questions.\n\nKodKodKod Learning Consulting\nhttp://www.kodkodkod.com
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In gap between the valence band and the conduction band is very high. Conductors have overlapping bands. Semiconductors have small gaps (e.g., Si=1.1eV). Insulators have high gaps (SiO2 about 8 or 9eV).
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Depending on the part of photography involved, you could be an optical engineer, dealing with the lenses, a mechanical engineer dealing with the camera shutter, (film) transport, and so on, an electronic engineer dealing with the electronics used in modern cameras for light measuring, focusing, and much more.  Semiconductor physics is involved deeply in digital cameras.  Chemical engineering is involved with film design, manufacture, and processing (development of pictures).\n\nI hope this sheds a bit of light on your question.
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Extremely difficult. Solar cells are semiconductor devices, just like computer chips, but less complex. Very expensive equipment and ultra-pure materials are required.
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http://en.wikipedia.org/wiki/Transistor\n\nIt's a big subject, at that is just a start.
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A metal-oxide-semiconductor (MOS) structure is obtained by depositing a layer of silicon dioxide (SiO2) and a layer of metal (polycrystalline silicon is actually used instead of metal) on top of a semiconductor die. As the silicon dioxide is a dielectric material its structure is equivalent to a plane capacitor, with one of the electrodes replaced by a semiconductor.\n\nWhen a voltage is applied across a MOS structure, it modifies the distribution of charges in the semiconductor. If we consider a P-type semiconductor (with NA the density of holes), a positive VGB ( gate base voltage) tends to reduce the concentration of holes and increase the concentration of electrons. If VGB is high enough, the concentration of negative charge carriers near the gate is more than that of positive charges, in what is known as an inversion layer.\n\nThis structure with P-type body is the basis of the N-type MOSFET, which requires the addition of an N-type source and drain regions.\n\nPMOS (′pē′mös) :\n\n(electronics) Metal-oxide semiconductors that are made on n-type substrates, and whose active carriers are holes that migrate between p-type source and drain contacts. Derived from p-channel metal-oxide semiconductor. \n\nNMOS (′en′mös)\n \n(electronics) Metal-oxide semiconductors that are made on p-type substrates, and whose active carriers are electrons that migrate between n-type source and drain contacts. Derived from n-channel metal-oxide semiconductor. \n\n\n--------------------------------------------------------------------------------\nNMOS:\n\nnMOS logic uses n-type metal-oxide-semiconductor field effect transistors (MOSFETs) to implement logic gates and other digital circuits. nMOS transistors have three modes of operation: cut-off, triode, and saturation (sometimes called active).\n\nThe n-type MOSFETs are arranged in a so-called "pull-down network" (PDN) between the logic gate output and negative supply voltage, while a resistor is placed between the logic gate output and the positive supply voltage. The circuit is designed such that if the desired output is low, then the PDN will be active, creating a current path between the negative supply and the output.\n\nAs an example, here is a NOR gate in nMOS logic. If either input A or input B is high (logic 1, = True), the respective MOS transistor acts as a very low resistance between the output and the negative supply, forcing the output to be low (logic 0, = False). When both A and B are high, both transistors are conductive, creating an even lower resistance path to ground. The only case where the output is high is when both transistors are off, which occurs only when both A and B are low, thus satisfying the truth table of a NOR gate:\n\nA B A NOR B \n0 0 1 \n0 1 0 \n1 0 0 \n1 1 0 \n\nWhile nMOS logic is easy to design and manufacture (a MOSFET can be made to operate as a resistor, so the whole circuit can be made with nMOSFETs), it has several shortcomings as well. The worst problem is that a DC current flows through an nMOS logic gate when the PDN is active, that is whenever the output is low. This leads to static power dissipation even when the circuit sits idle.\n\nAlso, nMOS circuits are slow to transition from low to high. When transitioning from high to low, the transistors provide low resistance, and the capacitative charge at the output drains away very quickly. But the resistance between the output and the positive supply rail is much greater, so the low to high transition takes longer. Using a resistor of lower value will speed up the process but also increases static power dissipation.\n\nAdditionally, the asymmetric input logic levels make nMOS circuits susceptible to noise.\n\nThese disadvantages are why nMOS logic was supplanted by CMOS logic both in low-power and in high-speed digital circuits, such as microprocessors, during the 1980s.\n\nPMos:\nFull details on:\nhttp://www.kettering.edu/~bguru/mosfets/PMOS-INT.pdf\n\nFor more info go to :\n\nht
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Static= Semiconductor Memory\nDynamic= Semiconductor Randon Access Memory
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Gallium based semi-conductor right now is too expensive to deploy. \n\nIf you want completely out of the left field, I'd go for optical processing.
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Solar power is a tricky field to understand....you need to understand p-n junctions, a brief introduction and explanation is here:\nhttp://www.pbs.org/transistor/science/events/pnjunc.html\n\nHere is a brief explanation...this stuff is everywhere on the web and in journals and books if you want specifics.\n\nUsing Silicon as an example which is the most common (this is a bit demonstrative and not completely realistic but should explain some stuff).\n\nTwo silicon wafers are made that are ultra pure and containing small amounts of impurities that are added in a controlled manner.  One wafer has impurities that are n-type, that is when they are in the silicon crystal they have three bonds (compared to the silicons 4) and a dangling lone pair of electrons (nitrogen and phosphorus based are quite common).  This silicon is considered to have electron rich impurities.\n   The p-type impurities in the other wafer are three-bonded as but do not have the lone pair (boron is common).  This silicon has electron poor impurities.\n\nWhen the two wafers are put into perfect contact (in practice the impurities are doped into a single crystal when it is made), electrons from the n-side transfer to the p-side.  This only happens a little bit...at first it is easy to do but as more and more electrons leave an electric field is formed in each half of the silicon that gets greater and greater as the electrons occur.  This field opposes further electron jumping and eventually this stops....an equilibrium situation occurs where both halfs of the silicon have transferred their electrons and charge stops moving.  Note this only occurs at the interface of the two wafers.\n\nBut when the silicon is hit by light, the transferred charges become mobile.  Charge transfer occurs by, (using the p-wafer as an example) an electron transferred to the p-side becoming mobile and moving far away from the interface to the back of the wafer where it is collected by a wire to transfer current to a device...the retun path of the circuit is through the n-side.\n\nI dont' do the process justice...the introduction in this link does a much better job...\nhttp://etd.caltech.edu/etd/available/etd-08062002-192958/unrestricted/Chapter1.pdf#search='semiconductor%20band%20bending%20solar%20power'
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try it... then you might want to go into details like integrated circuits ICs and transistors...\n\nhttp://en.wikipedia.org/wiki/Microprocessor