Elementary electronics and semiconductors

[bonildo]

Homework Statement

http://postimg.org/image/hf6zpmykr/

Homework Equations

intrinsic carrier density = ni = 10^10/cm^3 (for Si at 300K)

The Attempt at a Solution

Its a really elementary problem but I can't figure out the difference between some quantities. For example, free electrons and holes would be in same quantity since the bar isn't dopped? Valence electrons and free electrons are the same thing ? And I can't see a way to calculate the numbers of atoms.

 

[mfb]

For example, free electrons and holes would be in same quantity since the bar isn't dopped?

Right. And you have an equation that allows to find the product of those two numbers.

Valence electrons and free electrons are the same thing ?

No.

How many valence electrons per silicon atom do you have?
The number of atoms is independent of the semiconductor properties, but you'll have to look up material constants for silicon.