# Semiconductor doped with acceptors

1. Feb 24, 2017

### Kara386

1. The problem statement, all variables and given/known data
A semiconductor has an acceptor concentration of $6.7 \times 10^{16}$cm$^{-3}$, with no donors. Its intrinsic carrier concentration is $4.2\times 10^{17}$ at 650K.

What's the concentration of free electrons at 290K? Estimate the temperature of the crossover between intrinsic and extrinsic behaviour.

2. Relevant equations

3. The attempt at a solution
For the first part I've calculated $N_c, N_v$ so now I just need what the concentration of holes is, because
$np = N_c N_v e^{-\frac{E_g}{kT}}$

Where $N_c = N_v = AT^{\frac{3}{2}}$, and I used that equation at $T=650K$ to calculate A, which is the same at all temperatures then. So then I can use it to calculate $N_c,N_v$ at 290K. I'm not sure it's true that they're equal actually but I assumed so because the intrinsic carrier concentration is the same for electrons and holes. Now I think about it, maybe those two aren't equal, but I guess that's essentially the same problem - I don't know what the concentration of holes is! Is it the intrinsic concentration plus the number of acceptors?

As to the second part, no idea about the method for that.

Thanks for any help! :)

2. Mar 1, 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.