if the semiconductor is doped with impurities and if we don't apply external electric field. is it neutral?
439271
it is neutral. when u dope it lets say p type, there are free holes generated. however the dopant will be negatively charged as it has given up a hole (aquired a electron). so the total charge is zero and the material is neutral.
1055755
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.
1075073
well it depends, but generally they don't stay that way for long. They react with other atoms that are charged opposite of whatever they are. This is how chemical bonds are formed. It can either be a covalent bond in which they atoms are "sharing" electrons in order for both to be neutrally charged or they form an Ionic bond.
79059
The way that I have always determined whether or not an element or even device is passive or active is whether or not that device requires a source of electricity to perform its function.  For example, a resistor, capacitor, inductor, or even diode merely takes a signal and affects it in some manner consistant with its function.  A transistor, on the other hand, requires a third input to perform its function.  This would be true for IC's like op amps as well.  This distinction can also be extended to devices such as cavity combiners would be a passive element while an amplifier would be considered active.
924763
Since Ga is under Boron and Aluminum, which both have a valence of +3, you would expect Ga to behave the same way, losing electrons from the p and s orbitals (but not the d).\n\nSo b) GaI3 is correct
843449
maybe this would help\nhttp://encarta.msn.com/encnet/refpages/search.aspx?q=semiconductors
1088099
insulators ; conduction
463517
the external electric field creates an electric field in the copper. however, copper is a conductor so charge flows within the copper so that the net electric field is 0.
712708
The movement of a hole in p-type semiconductor is in fact the movement of electrons sequentially filling a valence band vacancy.\nThis means that holes tend to move at a lower speed than electrons would in the same material with the same electric field applied.\nWe measure the effective mass of the hole by applying a field to the material and seeing how fast the holes accelerate (Newton's Law)\n\nIf you look at the characteristics of complementry transistors, which are being sold as matched pairs, you will see the extra mass of the hole manifests as an inferior characteristic in the ptype carrier transistor or FET.\n\nA p-type carrier is a hole in a semiconductor.\nA positron is a hole in space that can be filled by an electron.  The hole in space has a mass, velocity and the opposite quantum numbers of the electron.\nHoles and positrons are not the same animal!!!!!!
790374
Not unless you can figure out a way to produce a semi-conductor at home.  Basically a solar cell (photovoltaic cell) is a couple of layers of silicon  P type and N type.  Electrons become excited when light quanta penetrates into the P layer. The excited electrons move to the N type and (very oversimplified) create electricity.\n\nI doubt you would have the facilities to create the materials at home.
120420
Assuming you mean photoelectric and not just solar heat cells: \nThe material (silicon ore = sand) is not the problem, the trouble is the apparatus needed to electrolyse and purify the material, and then apply it to suitable carriers.
1028768
Simply put, it's not a conductor. \n\nhttp://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA1/MVHTM/R0540/S567.HTM
124259
Its a class of compounds (doped silicon or germanium) that act as poor conductors until excited by a properly applied polarity. Doping refers to adding electron donors or electron acceptors. The material with electron donors added becomes N material, that with electron acceptors becomes P material.  When a PN junction is forward biased, that is, positive applied to P material and negative to N material, current flows with little resistance. When reversed biased, the resistance increases to millions of ohms.  What I've just described is a semiconductor diode.  A transistor is a PNP or NPN junction.
515612
Atoms do not have a charge.\nIons have a charge (either plus or minus)
74610
if we apply voltage across an insulator, charges pass through it.\nif we apply voltage(there is limit in the value of voltage) across an dielectric it will keep the positive and negative charges separate on the opposite surfaces of the dielectric material. those materials are used in making capacitor.
6440
Polarity of electricity was specified long ago by Benjamin Frankline before there was a practical means of detecting electrons.  He could have tossed a coin to specify + or -.  The thought was that electricity would flow (like water) from + (high) to - (low).  Unfortunately it was discovered that electrons actually flow from - to + in an external wire, but it was too late and we live with convention now.  In a way it really doesn't matter as long as all circuit designers agree on the convention since we can not see electrons; unless you are designing a vacuum tube (etc.) where electrons must physically flow from a heated element that boils them off to a grounded plate that collects them.  Cathode is normally the negative pole.
202706
An electric field exists around any electrically charged object... so all wires and components in a circuit will have an associated electric field. One circuit element in particular depends on the field to function: the capacitor. The capacitor simply consists of two parallel plates seperated from each other. Connecting the capacitor up to a voltage source creates an electric field on the plates which causes electrons to move away from one plate (the positive terminal) and move into the other (the negative terminal). The result is an excess of electrons on one side of the capacitor - which is stored energy.