How do you verify that the metals are obey the Ohm's law where as semi-metal are not?
I think a semiconductor material does obey Ohm’s Law. This of course includes the requirement of constant temperature.
Semiconductor devices dont obey Ohm’s law because of what happens at the junctions. There art two types of semiconductor labelled as p and n.
The p types have atoms which are short of an electron ( a hole where an electron could go). We think of these as being objects in the sense that if an electron goes into a hole it disappears and another hole appears where the electron moved from. WE think of conduction happenning because the holes move (it is electrons filling the holes that are doing the moving really)
N type semiconductors have atoms with an excess of electrons. Here the excess electrons are free to move and these do the conducting.
When you put them together and make a junction, the excess electrons from the n side of the junction go and fill the holes on the positive side. This results in a narrow region where there are no holes nor free electrons. This is called the depletion layer and this region does not readily conduct.
Now if you apply a pd and make a current flow one of two things can happen.
One way, the electrons which went into the depletion layer are pulled back out of the holes and the depletion layer disappears. The are holes in th p material and free electrons in the n material so the whole device conducts.
If you reverse the PD and try to make the current flow the other way, something different happens. More electrons from the n material move over to the p material and fill the holes, this makes the region with no holews or electrons , the depletion layer, even wider so it acts asa better insulator preventing further current flowing.
I have decribed the action of a diode that allows current to flow one way but not the other. This is not in keeping with Ohm’s Law.
I think a semiconductor material does obey Ohm’s Law. This of course includes the requirement of constant temperature.
Semiconductor devices dont obey Ohm’s law because of what happens at the junctions. There art two types of semiconductor labelled as p and n.
The p types have atoms which are short of an electron ( a hole where an electron could go). We think of these as being objects in the sense that if an electron goes into a hole it disappears and another hole appears where the electron moved from. WE think of conduction happenning because the holes move (it is electrons filling the holes that are doing the moving really)
N type semiconductors have atoms with an excess of electrons. Here the excess electrons are free to move and these do the conducting.
When you put them together and make a junction, the excess electrons from the n side of the junction go and fill the holes on the positive side. This results in a narrow region where there are no holes nor free electrons. This is called the depletion layer and this region does not readily conduct.
Now if you apply a pd and make a current flow one of two things can happen.
One way, the electrons which went into the depletion layer are pulled back out of the holes and the depletion layer disappears. The are holes in th p material and free electrons in the n material so the whole device conducts.
If you reverse the PD and try to make the current flow the other way, something different happens. More electrons from the n material move over to the p material and fill the holes, this makes the region with no holews or electrons , the depletion layer, even wider so it acts asa better insulator preventing further current flowing.
I have decribed the action of a diode that allows current to flow one way but not the other. This is not in keeping with Ohm’s Law.
