diodes - Transportation of holes

I was studying pn junctions and came across the concepts of diffusion currents. From what I understand is, when the junctions come together, since there is an excess of donors on the n side and an excess of a accdeptor impurities on the p side the concentration gradients force a cross junction diffusion phenomena. Now what I would like to know is that what are the particles that move to create the diffusion currents. The notes from where I'm learning says holes and electrons. Now the actual movement of electrons make sense, because atomic ionization is a pretty ordinary event, but what does it mean when they say that a "hole" crosses the junction from the p side to the n side? Does the entire acceptor atom separate itself from the crystal lattice of the semiconductor and cross the junction? It doesn't really make sense to me? Or is it some exotic effect which I'm unaware of?

Answer

In hole movement, the particles that are moving are still electrons. When an electron moves to the conduction band (i.e. at any temp above 0 K), there is an empty state that is created in the valence band that was originally occupied by the electron. This empty state is the hole. If another electron from the valence band moves to occupy this hole, it creates another hole one atom over. A chain of such electron movements could be thought of as a hole moving.

I think this is simplifying things quite a bit, but it gets the gist, and I don't really understand the more advanced version. :)

Edit : Actually, I'll try to include the advanced version, by just quoting from the excellent Daniel Mittleman from this awesome thread on the very related topic of 'Are holes real?', since most people probably can't access that thread.

... no such thing as a lone electron or, ... a lone hole - inside any solid. Any charged particle will interact with all of the other electrons, and nuclei, in the solid ...

... [With] These interactions .. taken into account ... One ends up describing what are called 'quasi-particles', which are excitations of the solid that, in some way, resemble a lone electron or a lone hole ...

It is not just semantics - [electrons and holes] are both equally real excitations of the many-body state of the solid.

So, while the simple picture generally enough for getting the drift of things, there's more beyond it, and there's a bit more to holes than just the absence of electrons.