1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Optical process in semiconductors

  1. Mar 26, 2008 #1

    Defennder

    User Avatar
    Homework Helper

    1. The problem statement, all variables and given/known data
    I'm trying to understand this part of my notes where the optical absorption in both indirect and direct bandgap semiconductors. This part specifically mathematically describes the change in energy and momentum of an electron in a semiconductor after it has absorbed energy from incident photon.

    Qn: Why is [tex]\hbar\vec{q} << \hbar\vec{k}[/tex]?


    2. Relevant equations

    http://img222.imageshack.us/img222/9665/qnmj5.th.jpg [Broken]

    This is the part I am referring to.

    3. The attempt at a solution
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Mar 26, 2008 #2

    G01

    User Avatar
    Homework Helper
    Gold Member

    Hmm, I am currently taking Solid State myself and am currently learning this material, but I'll try to offer some insight.

    I would think that [tex] \hbar\vec{q} << \hbar\vec{k}[/tex] would have to be true when you consider the wavelengths of typical electrons and photons.

    Remember that the magnitude of the wave vector for either electron or photon is:

    [tex] k=\frac{2\pi}{\lambda}[/tex]

    Where, for electrons, lambda is the DeBroglie Wavelength.

    An average optical photon has a wavelength of ~500nm, while the DeBroglie wavelength of an electron is in the picometer range, much, much smaller. So, how does this effect the relative values of k and q and thus, the values of [tex]\hbar k[/tex] and [tex]\hbar q[/tex]?
     
    Last edited: Mar 26, 2008
  4. Mar 26, 2008 #3

    Defennder

    User Avatar
    Homework Helper

    Oh yeah, you're right. That should be the explanation. Thanks.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...
Similar Threads for Optical process semiconductors Date
Optics - Diffraction grating Sunday at 1:28 PM
Must we always use absolute value for lens magnification? Friday at 3:20 PM
Number of images Apr 18, 2018
Contact Lenses Optics Problem (Two-Parts) Apr 12, 2018
Focusing process (Optics) Oct 24, 2007