# Anderson's rule semiconductors

1. Mar 8, 2017

### Kara386

1. The problem statement, all variables and given/known data
An InAs quantum well in AlSb has a bandgap of 1.58eV in AlSb, and a bandgap in InAs of 0.354eV. The electron aﬃnity of AlSb is $3.65eV$ and the electron aﬃnity of InAs is $4.90eV$. Is this a Type I, II or III heterojunction? Use Anderson's rule.

2. Relevant equations

3. The attempt at a solution
I'm ignoring the term quantum well, I think the important thing is that it's a heterojunction. I only want to check I've calculated the offsets correctly. By Anderson's rule, the conduction band offset is given by
$\Delta E_c = \chi_A - \chi_B$
And
$\Delta E_v = E_{g_B} - E_{g_A} - \Delta E_c$
So I assumed that material A is AlSb and material B is the InAs. So
$\Delta E_c = 3.65-4.9 = -1.25$eV
$\Delta E_v = 0.354 - 1.58 - (-1.25) = 0.024$eV
So I was thinking that if I've done that right, then the energy gap of the InAs should be the energy gap of the AlSb with the two offsets subtracted. But that isn't quite the case, because
$1.58 - 1.25 - 0.024 = 0.306$
So I suppose it's the right ballpark, but I just wanted to check if I've done that right. I think that means it's a Type I, because drawing a quick diagram I get something that looks very similar to this:
https://www.bing.com/images/search?...608020151900833127&selectedIndex=0&ajaxhist=0

Last edited: Mar 8, 2017
2. Mar 13, 2017

### PF_Help_Bot

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.