Why does Si donate its own electron to Al in a p-type semi conductor losing its own stability? Things I have known or been taught before asking this question:

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*Every electron does not absorb same amount of energy from the environment. So there are some electrons in a semiconductor which can absorb enough energy to leave their orbital and roam freely. They shift from valence band to conduction band.


*Free electrons usually do not fill up the holes of a p-type semiconductor


*Few bonding electrons of Si-Si leave their bonding electron to fill the holes generated due to doping. And this results in movement of holes throughout the material. It is comparable to resonance in a cation having $\sigma$-$\pi$-$(+)$ successive arrangement.
I have asked the following question based on these ideas which are perhaps wrong
Let's say we are talking about silicon semiconductor doped with aluminium or boron. All these are p-block elements and as far as I know they have been observed to be stable when their octets are filled. When Al or B is doped we all know that they will form covalent bonds (3 covalent bonds) with Si. As far as I know due to polarization Al forms covalent bond.
Now, since their octets aren't filled, they will tend to find a electron to form another covalent bond with Si. But why would adjacent Si donate one of its electron to Al? I mean aren't those Si's losing their stability too? Why would one atom lose its own stability to provide another atom stability? Is it the thermal energy gained from the surroundings which lets electrons to leave its location and move to another location (orbital), just as we see during the formation of atomic spectra?
I know all these things don't work that way as I have mentioned, there are a bunch of extremely sophisticated phenomena taking place during those moments. I don't want to dig that far (at least for now), but the least thing I can do is avoid wrong ideas, which is basically why I am asking this question.
 A: There are quite a few assumptions/claims in your question which are a bit confusing. Some of them, I don’t really understand what you meant, and I think they might point out some underlying confusions (which is fine). For example:

As far as I know due to polarization Al forms covalent bond

What do you mean by polarization, what do you think is polarized, and how do you think it relates to covalent bonding?.

Is it the thermal energy gained from the surroundings which lets electrons to leave its location and move to another location(orbital) just as we see during the formation of atomic spectra

 
I don’t understand the parallel that you are trying to establish between the atomic spectra and this situation. I also don’t understand the link that you seem to imply between thermal energy and the “formation” of atomic spectra. You could observe atomic spectra at 0K
 
Apart from this, I think your main question is:

But why would adjacent Si donate one of its electron to Al?

I think there is another misunderstanding implied in the formulation. Covalent bonds are not about donating electrons (that would be closer to ionic bonding). To keep it simple, it’s more about “sharing” them. You can check the wiki page for covalent bonding to learn more about it, it is an important distinction. Basically, two atoms forming a covalent bond will put an electron pair “in common”, so that they each have “one more valence electron”. So in your case Si, is not “losing” an electron; both Si and Al are “gaining” one.
 
As to the reason why Si is more than happy to share with his buddies, it is quite straight-forward to explain in simple terms. You already know about the octet rule. Well, silicon has four valence electrons. So it also wants to bond with 4 neighbours to obtain 8 electrons. Atoms are not particularly racist, so Si doesn’t care if it shares with another Si or an Al, as long as it gets its electron to satisfy its valence.
 
You’ll note that this answer does not address how that leads to doping and formation of free electrons or holes because your question has nothing that specifically relates to it (your doubts are "one step before" that). But you are welcome to ask questions about it later if you need.
