What is Band bending: Definition and 11 Discussions

In solid-state physics of semiconductors, a band diagram is a diagram plotting various key electron energy levels (Fermi level and nearby energy band edges) as a function of some spatial dimension, which is often denoted x. These diagrams help to explain the operation of many kinds of semiconductor devices and to visualize how bands change with position (band bending). The bands may be coloured to distinguish level filling.
A band diagram should not be confused with a band structure plot. In both a band diagram and a band structure plot, the vertical axis corresponds to the energy of an electron. The difference is that in a band structure plot the horizontal axis represents the wave vector of an electron in an infinitely large, homogeneous material (a crystal or vacuum), whereas in a band diagram the horizontal axis represents position in space, usually passing through multiple materials.
Because a band diagram shows the changes in the band structure from place to place, the resolution of a band diagram is limited by the Heisenberg uncertainty principle: the band structure relies on momentum, which is only precisely defined for large length scales. For this reason, the band diagram can only accurately depict evolution of band structures over long length scales, and has difficulty in showing the microscopic picture of sharp, atomic scale interfaces between different materials (or between a material and vacuum). Typically, an interface must be depicted as a "black box", though its long-distance effects can be shown in the band diagram as asymptotic band bending.

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  1. V

    A Nanowire with charge neutrality in band gap

    I'm working on a finite element simulation of the electrostatic potential V(r) in and around semiconductor nanowires, based on solving Poisson's equation. While the details of the problem will follow shortly, the crux of where I run into trouble is that for nanowires it is important to include...
  2. E

    I Double heterostructure junction in forward and zero bias

    Hi! When dealing with a pn homojunction, it is easy to see the features it has at equilibrium, and also the features it has with forward/reverse bias. Plots show the constant Fermi level at equilibrium and the different Fermi levels for a forward bias; moreover, examples show how much the bands...
  3. Y

    Band bending versus band sloping

    I'm trying to reconcile how a built-in potential can form in a semiconductor heterojunction in which there is a significant band cliff to majority carrier diffusion from both sides of the junction i.e. there is a cliff which should block hole diffusion from the p-type as well as a cliff which...
  4. R

    Band bending, depletion layer thickness, density of occupie

    Homework Statement Consider an n-type Si (Eg =1.1eV, ED=EC, εr=11.8) with a bulk doping density ND=1×1017cm-3, a density of acceptor type surface state 1×1014 cm-2 and these states are at the middle of the band gap. Evaluate the amount of: a) band bending b)depletion layer thickness c) density...
  5. O

    How does band bending occur in condensed matter physics?

    I'm trained in Condensed Matter Physics, and I'm trying to learn EE. The concept of band bending always baffled me a bit. Here's why: The band edge bloch states are delocalized over the whole of the crystal, and have fixed given eigenvalues. How can this eigenvalue change over the length of the...
  6. H

    What is band bending and how does it relate to Fermi Energy?

    Homework Statement Consider a pn junction in Si at 300K (other parameters given), with doping NA = 1021/m3 and ND = 1023/m3. Assume all impurities are ionized. On this basis find the Fermi level on each side. From this find the band bending VB and make a sketch of the pn junction. Homework...
  7. 1

    Band Bending at SiO2 Interface

    Hello everyone ! In below picture we can see band bending in semiconductor at SiO2 interface, as show in picture how charge's BE(binding energy) and KE(kinetic energy) are changing..?? Or what happens to charges total energy in band bending ..?? \\
  8. F

    Upward Band Bending in n-Type Si Contacted by Metal

    I am a little bit confused about the upward band bending in a n-type Si which is in contact with a metal. Suppose that electrons flow from Si to the metal to align the chemical potentials such that positive donor levels become depleted. In equilibrium one ends up with a negative charge density...
  9. F

    Band Bending & Donor Concentration in Semiconductors

    When a n-type semiconductor is brought into contact with a metal, then alignment of the chemical potentials of both systems leads to band bending within the depletion layer, e.g on the semiconductor side. does the amount of band bending (change of potential) also depend on the donor...
  10. F

    Band bending in a thin film semiconductor

    Hello! There're very thin (4-15 nm) semiconductor films (passive film) formed on stainless steel by electrochemical method. In a electrochemical cell, I applied potential on stainless steel electrode to adjust Fermi level of the semiconductor passive film. I think that band bending take place...
  11. J

    Schottky contacts - band bending

    Hello! I am looking a bit at the Schottky contacts, metal-semiconductor, and I am starting to get a hang of it, but some things are missing. Specifically: Why must the distance from the Fermi Energy to the vacuum level in the metal and the distance from conduction band edge to vacuum...