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Homework Help: What happens when semiconductor melt?

  1. Feb 11, 2008 #1
    1. The problem statement, all variables and given/known data
    For intrinsic (undoped) silicon with a band gap of 1.1eV at 1500 K, what is the population of conduction electrons (m-3)? Comment on your result. Note that the melting point of silicon is 1687 K, and atom density of silicon is 5 x 10^28 atoms m-3.

    Note: My main problem is to "comment"

    2. Relevant equations
    http://hyperphysics.phy-astr.gsu.edu/HBASE/solids/fermi3.html#c1 <-- see here for the steps taken
    In the end, I got 3.96x10^22 electrons/m3 which is close to the one given by the applet (maybe 'cos I used different values)

    3. The attempt at a solution
    I was thinking of writing something like:
    Although this equation may imply that increase in temperature will lead to increased conductivity (because increased no. of conducting electrons), we have to consider the state of the matter in which it is in. At higher temperature such as 1700 K, melting would have occurred. This may result in lower value of conductivity calculated than the actual. This is because melting would have caused the semiconductor to be in liquid state. Thus, the positive metal ions can carry charges along with the sea of electron.

    But I'm not too sure if the bold sentence is correct. I would really appreciate it if you guys can give me some feedback on this answer.

  2. jcsd
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