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Why in intrinsic semiconductors do you need to apply very high potential to transfer electrons from the valence band to the conduction band?
Semiconductors, in the absence of applied electric fields, act a lot like insulators. In these materials, the conduction band and the valence band do not overlap. That's why they insulate. And that's why you have to apply some serious voltage to them to shove the valence electrons across the gap between the valence and conduction bands of these semiconductor materials. Remember that in insulators, there is a "band gap" between the lowest Fermi energy level necessary to support conduction and the highest Fermi energy level of the valence electrons. Same with the semi's. In metals, the conduction band overlaps the valence band Fermi energy levels. Zap! Conductivity.
What else can I help you with?
Why fermi energy level is midway between conduction band and valence band in semiconductors?
To be exact EF should be at the valence band edge (EV) at 0K because no energy state above EV are occupied at 0K; however, for intrinsic semiconductors there are no states in the band gap anyway, so placing the EF anywhere in the band gap including conduction band edge does not add any states as being occupied. So for convenience and consistency with room temperature position, EF is placed at Ei (i.e. room temperature intrinsic Fermi level position).
Why fermi level lie close to conduction band in p-type semiconductors?
The Fermi level moves to wherever it needs to be to assure that the overall system is charge-neutral. In an n-type semiconductor, we introduce fixed positive charges (donors), which must be balanced by mobile negative charges (electrons). The excess electrons must reside in the conduction bands, because the valence bands are full. To have excess electrons in the conduction band, the Fermi level (electrochemical potential for electrons) must lie near the conduction band. A similar argument can be made for p-type doping
What roles do free electrons and holes play in intrinsic semiconductor?
Free electrons and holes are the charge carriers-not only in intrinsic semiconductors(these are the purest form of semiconductors-typically as pure as can be made available with the present technology) but also in extrinsic semiconductors(doped semiconductors).In intrinsic semiconductors,electron-hole pairs are created due to the natural processes like-absorption of heat energy from the surroundingsabsorption of energy from photons.this absorbed energy results in breakdown ofcovalant bonds in intrinsic semiconductors as a result of which electron-hole pairs are created.It is this electron hole pair which is responsible for carrying the current through the intrinsic semiconductor when a potential difference is applied across it.In extrinsic semiconductor the case is slightly different-here, we have-majority charge carriers and minority charge carriers.in an n-type semiconductor-majority charge carriers are the electrons contributed by the pentavalent impurities while the minority charge carriers are the holes which are generated as electron-hole pairs due to natural processes discussed above.in p-type semiconductor-majority charge carriers are the holes contributed by trivalent impuritieswhereas the minority charge carriers are the electronswhich are generated as electron-hole pairs due to natural processes discussed above.these are the majority charge carriers which contribute heavily in the flow of current through the extrinsic semiconductors than the minority charge carriers.I suggest you to please go through mass action law and law of electrical neutrality of semiconductors for better understanding.
The subatomic particles that move in response to a potential difference are called?
The subatomic particles that move in response to a potential difference are called electrons. These negatively charged particles flow from areas of high potential to low potential in a process known as electric current.
What must be present for conduction to occur?
For conduction to occur, there must be a material with free electrons, such as a metal, to allow the flow of charge. Additionally, there must be a potential difference (voltage) across the material to drive the flow of electrons. Finally, the material should be a conductor, as insulators do not allow for the flow of charge.
Conduction along a myelinated axon is called?
It is called saltatory conduction. This describes the "jumping" of an action potential from node to node on a myelinated axon.
Why does a battery work?
A battery s a source of constant potential difference , this potential difference drives the electrons present in the wire and this constitutes current .Shortly the potential difference across the battery terminals does work on the conduction electrons present inside the conductor. Actually a battery is an electrolytic device ,after some time the electrolyte completely exhausts this state of battery is called as discharged state.
What is a electrical conduction?
An electrical conductor is a material whose molecules contain loose valence electrons that can easily be passed between molecules. When an electrical potential difference (aka voltage) is applied to the surface, the electrons drift toward or away from it (depending on the charge) - this is referred to as the conduction of electricity.
How is saltatory conduction different from continuous conduction?
Saltatory conduction occurs in myelinated neurons where the action potential jumps from one node of Ranvier to the next, speeding up the transmission of signals. In comparison, continuous conduction occurs in unmyelinated neurons where the action potential moves along the entire length of the axon, which is slower than saltatory conduction.
What is the intrinsic stand off ratio of UJT?
the amount of potential to forward bias it
What does intrinsic stand off ratio of an ujt determine?
The amount of potential to forward bias it
What happens to metals as they conduct electricity?
The electrons in a conductor will support the movement of electric current. A conductor is defined as a material with a number of electrons in its makeup that are actually in what is called the conduction band. The conduction band is an energy level where electrons must be to permit conduction in a material. If the minimum energy in the conduction band in a material is such that a lot of electrons in that material are already at or above that level, then these electrons will be available to support current flow. Remember that electron current flow is moving electrons, and it is not about sending an electron into a conductor, like a wire, at one end and getting that same electron out at the other. It is about sending a bunch of them in at one end, and all the electrons already in the conductor move over and a bunch come out the other end. The electrons already in the conduction band within the conductor support current flow in this way.
