Silicon and Germanium Semiconductors Doped with Antimony

Colleges & Universities University of California - Berkeley
1

<p>Why would an intrinsic silicon semiconductor which is doped with antimony and with density of donor atoms of 10^14 per cm^3 be n-type at a temperature of 400 kelvin, while a germanium semiconductor with the same doping be p-type? I mean, since antimony is a group V element, shouldn’t it always ionize to give a free electron. I think it might have something to do with the density of state’s effect on the fermi level.</p>

2

<p>

</p>

<p>I think so too.</p>

3

<p>I think it might be magic.</p>

4

<p>To anybody who is currently taking EE130: have any mathematical description of solution?</p>

5

<p>collegeconfidential.com=/=cramster.com</p>

6

<p>Sigh… another group of people afflicted with neurotypical syndrome.</p>

7

<p>It totally depends on where the antimony energy levels are while sitting in a crystal of silicon or germanium. If there’s a full energy level near the conduction band edge, then the antimony can be easily ionized and will dope the semiconductor n-type. If there’s an empty level near the valence band edge, the opposite happens.</p>

<p>The III/V acceptor/donor picture can be a useful cartoon, but it only captures a small slice of reality. Don’t confuse the map for the territory.</p>

8

<p>[Physics</a> of Semiconductor Devices - Solved Problems with Theory: Vol. 1](<a href=“http://free-zg.t-com.hr/Julijan-Sribar/preview/vol1.html]Physics”>http://free-zg.t-com.hr/Julijan-Sribar/preview/vol1.html)
<a href=“http://ece-classweb.ucsd.edu/fall08/ece230a/hw3solution.pdf[/url]”>http://ece-classweb.ucsd.edu/fall08/ece230a/hw3solution.pdf&lt;/a&gt;&lt;/p&gt;

<p>see if you can make sense of any of that. ctrl+f is your friend. but idk. gl.</p>

9

<p>Sb-doped Ge is n-type.</p>

10

<p>I know you are but what am I.</p>

11

<p>Okay, I believe I have figured it out. First you calculate the intrinsic carrier density ni at 400k. Next you use the law of mass action and law of charge neutrality to calculate the thermal equilibrium of electrons and holes. Using the last calculation you find that the number of holes is very similar to the number of electrons in Ge. This is due to Ge’s smaller band gap, and thus a smaller operating temperature. Therefore it becomes intrinsic at higher temperatures no matter how much doping is added.</p>