what is the need of semiconductors than conductors?
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go for X  class' lakhmir singh & manjit kaur book
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An example of a conductor (of presumably heat and electricity) are any metal, such as gold, silver, nickel, platinum, iron.\n\nAn example of an insulator is rubber.
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Before transistors, radio tubes were used in electronics.  These were extremely bulky and consumed a ton of energy.  Since space and energy are in short supply in space travel, the transistor made things a lot easier.
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n doping a semiconductor introduces energy levels just below the conduction band. Because the conduction band is vacant, electrons can be excited from the n-doped band into the conduction band easily, and so can conduct (conduction relies on vacant states withing kT of the chemical potential).\n\np doping introduces energy levels just above the valence band. Electrons can jump from the filled valence band to the p levels to leave conducting "holes" behind.
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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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Metal Oxide Semiconductor Field Effect Transistor.  It's the basic component of most electronic circuits and all digital ones.  It's the breakthrough that made computers so cheap, small and popular.  A transistor, you know, acts as an electrical "gate," acting on a smaller input voltage to allow a larger voltage to pass through.  So a transistor can act as an amplifier, by using a smaller current to control a larger current.  Used in a circuit called a "flip-flop," it makes up the basic circuit for computers and other digital electronics.\n\nThere are many kinds of transistors, dating all the way back to vacuum tubes; the reason MOSFETs are such a big deal is because they are made by "printing," in huge quantities and on extremely small scales, directly onto microchips.
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Metals are shiny and are good conductors of heat and electric current. They are malleable and ductile.\nNon-metals are dull, and are poor conductors of heat and electric current. They're brittle and unmalleable.
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If the conductance band is very narrow, it results in a very high effective mass for the carrier.  This is because: giving velocity to the carrier increases its total energy.  If this total energy isn't within the band then the carrier can't be given it and so moves slowly.\n\nYour case would seem to be an N type good conductor,possibly a metal.
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good conductors are material with very tight atomic structure. Remember you are talking about electron flow here. they flow best and easies through material with very tight atomic make up like lead gold copper aluminum silver so forth. Most good conductors are non ferrous metals. This means If you heat them up to melting point they will not get red hot first, you will see very little color change in them from solid to liquid state.
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Pentavalent atoms theoretically require something other than Hydrogen to stay electrcally neutral.Again theoretically Trivalent atoms can not stay electrically neutral.
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maybe this would help\nhttp://encarta.msn.com/encnet/refpages/search.aspx?q=semiconductors
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Semiconductors are used all over the place, as others mentioned. \n\nSuperconductors have a number of applications, too, but their need for extreme cooling in order to operate limits their use. \n\nSome currently used applications for superconductors:\n\nSMES systems (Superconducting Magnetic Energy Storage) used in the power grid and at certain high power raw facilities. \n\nMagnets for MRI systems.  Superconductors make for fantastic electromagnets since the current moves through the coil without resistance\n \nElectromagnets in particle accelerators.  All modern particle accelerator facilities use superconducting magnets.\n\nHTSC SQUIDs.  These are "high T-sub-c Superconducting Quantum Interference Devices" which are a very sensitive sort of electromagnetic sensor based on a Josephson junction device.  These are used by the military, specifically the navy, to sense mines and submarines by the electromagnetic disturbance a large piece of metal makes in seawater. HTSC SQUIDs also have brain sensor applications and may someday result in technology that makes it possible to very accurately observe human brain activity with an easily transportable device.\n\nSuperconducting generators.  Just as superconductors make for excellent electromagnets, they also make great electrical generators.  The use of them is limited, but demand is growing.\n\nUltra high power electric motors.  Although not in widespread use, superconductors can be used to make very powerful electric motors.  The record so far is a 5000 horsepower motor.    \n\nRapid discharge of a SMES has also been used to make an "e-bomb".  This is an EMP (electromagnetic pulse) type weapon that can disable electronics and communication devices.  SMES make a perfect basis for EMP generation because of the huge energy density and rapid discharge.  The first field use of a SMES based e-bomb was in Iraq in 2003.
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Because a Diamond is made of pure carbon and it has not freely moving electron around inside it. Unlike metal for example. Also Except for most blue diamonds, which are semiconductors, diamonds are good electrical insulators. Blue diamonds owe their semiconductive property to boron impurities, which act as a doping agent and cause p-type semiconductor behavior. Blue diamonds which are not boron-doped, such as those recently recovered from the Argyle diamond mine in Australia that owe their color to an overabundance of hydrogen atoms, are not semiconductors.
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Carbon and ceramics are good insulators.\n\nGood conductors are copper and gold, to name a few.
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In certain low volume and high speed circuits, transistors will always have their places. ALthough their are now many more radio chips.\nMIKE
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While semiconductors do have a resistance, you can't read it by color. It isn't even constant, which is what makes semiconductors so useful. \n\nResistors, which are not semiconductors, are often marked with a color code that can be read this way:
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Copper is a pure metal. The conductivity of metals increase with temparature owing to decrease in the vibration of the +ve ions in the crystal lattice. Germanium is a semiconductor. Its conductivity decreases with temparature. Hence copper has more conductivity than Ge at low temps.