Chemical analysis of a germanium crystal reveals indium at a level of 0.0003091 atomic percent. Assuming that the concentration of thermally excited charge carriers from the Ge matrix is negligible, what is the density of free charge carriers (free carriers/cm3) in this Ge crystal?

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anonymous · Answer

If there are no thermal quasielectrons, all your charge carriers are from the holes created by the In dopant atoms, one hole per atom, so the atom percent given is the number of holes per 100 Ge atoms.  Now you just need to figure out the mass of 100 Ge atoms, and then (using the density), the cm^3 this would be.

anonymous · Answer

It's amazing how many edX homework questions I'm finding on OpenStudy. Cheating has become a habit.

anonymous · Answer

Not to worry, it's self-punishing.  What do you think happens when you land a job with false credentials and screw up in the first few months?  Hint: it takes many years to recover from the fallout.

anonymous · Answer

Seems like Carl speaks from experience :)

anonymous · Answer

Quite right.  I've fired people like that.  As well as bounced them out of graduate programs.  That can be an extremely sad and distressing duty.