Recent content by epsilonjon

Right okay. So I guess the answer to my original question is: both.

Really :confused: If the diode is forward biased then the external voltage is positive on the p-type and negative on the n-type. The positive voltage attracts electrons, so it increases the electron diffusion current to the left (in the diagram above). The negative voltage attracts holes, so...

Are you sure you're correct? The book I'm reading has a diagram similar to the one below, showing the hole diffusion in the valence band. I cannot see any reason why they wouldn't diffuse. You have a concentration gradient, the energy gap is reduced due to the forward bias, what is stopping...

Okay, so I guess holes do exist in the conduction band, but it really just looks like electrons. But still, what I really want to know is whether the holes in the p-type valence band are diffusing across the junction and through the n-type valence band (when the diode is forward biased)? Thanks.

Ah yeah, I see, thanks. I just still want to clarify about the hole diffusion current though, after the depletion region is formed, when you forward bias the diode. I think that holes travel through the valence band of the p-type, across the junction, and diffuse through the valence band of...

Thanks for the reply. So why do these electrons drop straight down to fill the acceptor holes near the junction rather than diffusing further into the material (exponential decrease in concentration as you move through the material) as is the case with the diffusion current? Is what I said in...

Still a bit stuck on this. Whatever way I try to think about it I come to a problem. In general for the diffusion currents, I think the hole current is facilitated by valence electrons in the n-type material diffusing in the opposite direction and filling those holes. If this wasn't the case...

Hi. I am reading about the pn junction, but I have a question. When the junction is formed the holes in the p-type material close to the junction diffuse across due to the concentration gradient. This leaves the acceptor atoms in the p-type material negatively charged. My question is: when...

I think maybe this got no replies because it's been asked/answered before? :confused: Apologies if that is the case. I saw an old thread here from 2003 but it didn't seem to answer my question. I'd still really appreciate any help as it's bugging me big time. Thanks, Jon.

Hi. I have read some QM and am trying to use it to understand why the noble gas configuration is the most desirable for an atom. It is my understanding that an anti-symmetric spatial wavefunction has a lower energy, since the electrons tend to be further apart. This means that the atom will...

That definitely makes it clearer. Thanks for your help :)

But then how do you know that the spin state being symmetric under exchange of particles implies the spatial wavefunction is anti-symmetric? I thought this came from the fact that the total wavefunction is \psi(r)\chi(s)?

Ah okay, I think I see that. So for 3 or more particles the spin wavefunction is always symmetric, meaning that (for fermions) the spatial wavefunction has to be anti-symmetric? Assuming no spin-position-coupling, the total wavefunction is \psi(r_1,r_2,r_3) \chi(s_1,s_2,s_3). But if I use the...

Hi. I'm currently working through Griffith's Introduction to QM, and have gotten to the section on the periodic table. I'll explain my understanding a little bit... Before this he's been looking at the Hamiltonian for helium: H = \left[ \frac{- \hbar ^2}{2m}\nabla _1 ^2 - \frac{1}{4 \pi...

Oh wow, that's interesting! Thanks :-)