What is Depletion region: Definition and 29 Discussions

In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile charge carriers have been diffused away, or have been forced away by an electric field. The only elements left in the depletion region are ionized donor or acceptor impurities.
This region of uncovered positive and negative ions is called the depletion region due to the depletion of carriers in this region.
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. Understanding the depletion region is key to explaining modern semiconductor electronics: diodes, bipolar junction transistors, field-effect transistors, and variable capacitance diodes all rely on depletion region phenomena.

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  1. C

    Engineering Depletion region capacitance in MOSFET

    I would like to ask about the behavior of a MOSFET as a capacitor, particularly at the onset of inversion/weak inversion - see Fig 2.6(c) At this stage in Fig 2.6(c), there is positive charge at the gate metal/poly contact, then an insulator oxide and then negative ions (positive holes have...
  2. Wrichik Basu

    Do carriers move across a p-n junction at 0 K?

    Often a band diagram is used to explain what happens when two pieces of the same semiconductor, one p-doped, one n-doped, are put together. I am a little confused about it, so here is my question. Initially and at ##0\mathrm{K}##, the surplus carriers should be confined to their respective...
  3. K

    B A couple of questions about diodes and the depletion region

    In a diode, we have N side, P side, and a depletion region, made of positive and negative charged sides. N side and P side of the diodes are neutral charge. In N side there are free electrons. In the positive charged side of the depletion region, there are positively ionized atoms that "lack"...
  4. G

    I Relationship between the depletion region and the band gap of a diode?

    Hi, Lately I've been reading about a lab exercise in which Planck's constant is estimated using LEDs. Every procedure I've encountered states that the energy of an emitted photon (and by extension the potential across the semiconductor's band gap) is equal to the threshold voltage multiplied by...
  5. A

    Effect of Doping on Depletion Region Width

    In an unbiased p-n junction, how does increase in doping affect the width of Depletion Region? I read somewhere that width decreases as increase in carrier concentration leads to more recombination of majority carriers with oppositely charged ions of their depletion regions leading to a...
  6. A

    I Depletion region and Schottky Barriers

    I am having some trouble understanding the physics behind the formation of Schottky Barriers. According to the convential theory, the idea is that for an n-type semiconductor the electrons in the conduction band can lower their energy by filling empty states in the metal. This in turns creates a...
  7. G

    Depletion zone and current in forward-biased PN junction

    Hello. I've learned that in PN junction, forward-biasing on it pushes holes in P-type and electrons in N-type toward the junction so depletion width is reduced. Is it due to that in N-type side(P-type side), pushed electrons (holes) are recombined with holes (electrons) in depletion zone? And...
  8. G

    Depletion zone and current in forward-biased PN junction

    Hello. I've learned that in PN junction, forward-biasing pushes holes in P-type and electrons in N-type forward junctions so depletion width is reduced. Is it due to that in N-type (P-type), pushed electrons (holes) are recombined with holes (electrons) in depletion zone? And what is true...
  9. pyctz

    Why is the electric field zero outside of depletion region?

    why do electric field is zero out side of depletion region?
  10. H

    Is E-field in pn-junctions changing linearly with bias?

    Hi guys, there are a lot of textbooks and articles describe the electric field in depletion region at thermal equilibium, but very few of them tell what happens to the field under bias. I am wondering if the electric field in the depletion region simply changes linearly with reverse bias? Or if...
  11. Y

    Depletion region vs Film thickness

    Here's something I can't get my head around: Take a diode (can be schottky, p-n etc) where the predicted depletion region is larger than the actual thickness of that layer will ever be. What happens? I've seen papers where its assumed that this curtails the built in potential. But it sounds...
  12. P

    Depletion region in n-type ohmic contact

    Hello every one, Here in below figure we can see an ohmic contact formation between a metal and n-type semiconductor . Here how the N-type semiconductor bands are banded upward ? and what type of depletion charge exists there ?
  13. H

    Double Layer or Depletion Region?

    Hello everyone, Recently I have been studying double layers. As I have studied I have realized that there seem to be a lot of similarities between a double layer and a depletion region in a PN junction. The each form electric fields (and thus have a capacitance) and they each limit (or...
  14. A

    Is the P-N junction the only means to acheive a depletion region?

    Hi, I have a quick question. When constructing a semiconductor diode, the P-N junction is used to create a depletion region (depleted of mobile majority carriers) which is the active volume of the diode/detector. The region enables an electric current generated from the incomming radiation to...
  15. I

    Solid state depletion region

    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
  16. 1

    MOS-Capacitor: Investigating Depletion Region Neutralization

    Hello everyone, My question is about MOS-capacitor, We know that, If we place +ve gate voltage on p-MOS capacitor holes are repelled from semiconductor-oxide interface leaving behind negative charge due to ionized acceptor ions,This results in a depletion region. Now the question is, If we...
  17. A

    Origin of the depletion region in a p-n junction

    Hi the first step to this is usually described as diffusion of electrons from the n type to the p type. However I have encountered sites and books that state that holes diffuse from p type to n type as well. I am of the opinion that only the electrons diffuse, and that there is no diffusion of...
  18. E

    Specfic question about the formation of the depletion region in a pn junction

    Hi. I am reading about the pn junction, but I have a question. When the junction is formed the holes in the p-type material close to the junction diffuse across due to the concentration gradient. This leaves the acceptor atoms in the p-type material negatively charged. My question is: when...
  19. V

    Why does the width of depletion region is small in highly doped diode?

    Dear, In Zener Diode, In highly Doped diode,the breakdown(Zener breakdown) occurs in small voltage.How? Thanks& Regards, Viswanathan.M
  20. azizlwl

    Depletion region- diode

    At depletion layer of p region, there more negative ions thus negatively charged region. Likewise at n region, it is positively charged. Then why in equivalent forward bias the diode behave as a battery of .7v with positive at depletion region of the p region where it is negatively charged?
  21. R

    Depletion region formation?

    How the depletion region act as capacitor? My view is that there are no charges because if formed of recombination of charges. so, there is no charge... So, how can it act like a capacitor? How the electric field is created in depletion region? It's confusing me a lot ...
  22. K

    Effect of Doping Levels on Width of Depletion Region

    Homework Statement The problem is what would be the effect on the width of the depletion region of an unbiased PN junction on the doping levels of the P and N sides Homework Equations This is a conceptual question. There is no equation involved. The Attempt at a Solution Increase...
  23. B

    What is the Depletion Region in NMOSFET Transistors?

    Hello, I am a bit confused about depletion region in NMOSFET transistor. It says here in my book, that when you increase Uds (drain source) above Ugs(gate source) that the current get higher. Ok, makes sense if nothing, from Ohms law. Simultaneously, the depletion region get smaller in...
  24. N

    Calculating Densities and Width of Depletion Region in Ge

    Homework Statement a. The densities of electrons and holes required for the Fermi levels in both the p- and n-type Ge to enter the bands. That is, in n-type Ge the Fermi level coincides with the bottom of the conduction band and for p-type Ge the Fermi level coincides with the top of the...
  25. S

    Understanding the width of the depletion region in a p-n junction

    I am studying to become and electrical engineer and am currently taking Electronics I. I am having trouble understanding the change in the depletion region that results from a bias. I understand that at the time of manufacture the free electrons from the n-type semiconductor are attracted to the...
  26. N

    [semiconduction] Does reverse bias decrease depletion region?

    Hello, For simplicity's sake, let's take a np junction. Say we connect the left side (n-pole) to a POSITIVE voltage; this is called a reverse bias, because it will result in a small current from n to p. In other words: electrons will travel from p to n across the junction (and holes will...
  27. O

    What determines the thickness of depletion region of a given p-n junction diodegiven

    Hello all, I am somewhat confused in understanding the depletion region of a p-n junction diode.Everywhere a depletion region is defined as a region near the p-n junction which is devoid of charge carriers.And the formation of this region is said is explain that it is due to the diffusion of...
  28. M

    Depletion region in pn juction

    Regarding the formation of depletion region,it forms because free electrons diffuse into p region from n region. after some recombination of holes, a sufficient potential difference is set up to prevent further diffusion. Now, consider the region to the left side of juction(whole P region...
  29. J

    Depletion Region shrinks with increased temperature

    Hi, Quick question. In a PN junction, the depletion region will shrink with an increase in temperature. Why is that? Is the Fermi energy of the p and n semiconductors a function of temperature? Thanks! Jax
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