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iScience
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how does letting the electrons diffuse to the P material/region lead to a "depletion" region in the center where the N and P material meet? please go into detail
Why would they do that?iScience said:simon bridge: okay then, whenever i say "current" i will be referring to electron current, NOT the hole current.
here's my understanding; the PN junction comes in contact, the electrons diffuse across the junction into the P material (diffusion current),
then there is an E-field set up across the junction since the materials are no longer neutral. the electric field forces electrons back to the N material and now we have our drift current. My professor said that the depletion region was the region where the electrons are mostly gone but not completely. he stated that when the diffusion current = drift current, then the system is in equilibrium and this is when the depletion region is set up.
How indeed - in a completely depleted depletion region, all the acceptor and donor sites will be ionized, so there will be no surplus charge carriers there. (You know how materials get to be P-type of N-type?)but whether or not there is a net current of zero, does not mean there is NO current at all. if there are currents flowing from the P to N, and N to P materials, then that still implies that there exists current; ie.. charge still has to flow from one side to the other. so how then, is the depletion region depleted of electrons?
You mean apart from empirical observations supporting this claim?i am not convinced because i don't have any reason to believe that there should be any less charge carriers in the depletion region than there are anywhere else in the entire semiconductor.
Simon Bridge said:Why would they do that?
Simon Bridge said:How indeed - in a completely depleted depletion region, all the acceptor and donor sites will be ionized, so there will be no surplus charge carriers there. (You know how materials get to be P-type of N-type?)
Are there any other sources of charge in the material?
If the current dropped to zero, not just the "net current but all movement of charge, would you feel better about this?
Simon Bridge said:You mean apart from empirical observations supporting this claim?
You appear to be happy that electrons, for instance, can move from their donor site into the P region? Then what does it leave behind?
... so you don't think that the atoms that make up the main body of the crystal have electrons and protons in them?any other sources of charges? no, just the donor and acceptor ions.
Simon Bridge said:... so you don't think that the atoms that make up the main body of the crystal have electrons and protons in them?
iScience said:i want to know the physics behind it.
electron moves from N→P, then it leaves behind a hole. I'm not sure where to go with this though.
But it may be your understanding is different - are you thinking that n-type material has a net negative charge?
Use the empty seat model ... n-type material has all the seats full and p-type material has all empty seats. Remove a wall between the two and people from the full-side of the auditorium start to shift over into the empty seats ... when someone moves, they leave an empty seat behind them. But they are unsure about whether this is OK so they don't go very far from their assigned seat.
You end up with scattered occupied seats close to the boundary on the p-side and scattered unoccupied seats close to the boundary on the n-side.
The 'depletion region' is so named because it is formed from a conducting region by removal of all free charge carriers, leaving none to carry a current
In either material you have mobile and fixed charges. When a mobile charge moves, it leaves the fixed charge behind. The mobile and fixed charges are a model used to approximate the behavior of the bulk material. They are derived from the presence of donors and acceptors - the fixed charges, the lattice charges, come from the fixed-in-place donor and acceptor ions.iScience said:when you say lattice charge are you referring to the N and P materials? ie the lattice charge of the N material being positive?
The charge carriers in the depletion region are not free. The depletion region is formed only after recombination of holes and electrons... so in the depletion region there are only and only immobile positive and negative ions... hence,there is no charge carrier...i still don't understand; because the depletion region is said to be the region that is depleted of all free charge carriers by wikipedia.
Simon Bridge said:The charge carriers in the depletion region are not free. The depletion region is formed only after recombination of holes and electrons... so in the depletion region there are only and only immobile positive and negative ions... hence,there is no charge carrier...
http://www.asdn.net/asdn/physics/p-n-junctions.shtml
Well sure - perhaps I should have made that clear :)nasu said:This is an exaggeration or simplification, at least.
There is a gradient of carrier concentration (both types) over the depletion region.
A solid state depletion region, also known as a depletion zone, is a region in a semiconductor material where there are no mobile charge carriers, either electrons or holes. This is caused by a difference in the doping levels of the material, creating a barrier to the movement of charge.
A solid state depletion region is formed when a material is doped with impurities, either by adding atoms with an extra electron (n-type doping) or atoms with a missing electron (p-type doping). This creates an imbalance in the number of electrons and holes, leading to the formation of a depletion region.
The purpose of a solid state depletion region is to create a barrier to the flow of charge in a semiconductor material. This allows for the creation of devices such as diodes and transistors, which rely on the control of charge flow through the depletion region.
The width of a solid state depletion region can greatly affect the performance of a device. A wider depletion region can create a larger barrier to charge flow, resulting in a higher breakdown voltage for devices such as diodes. However, a wider depletion region can also lead to slower device response times.
Yes, a solid state depletion region can be manipulated through various techniques such as applying a voltage, changing the doping levels, or using light to create additional charge carriers. These methods can alter the width and characteristics of the depletion region, allowing for control over device performance.