I like the way you have explained the inner workings of how a current moves. This is the clearest explanation I have seen so far. I was searching the net to find a good explanation of how semiconductors work. I was frustrated until I saw your article. It seems to be that you have a natural ability to explain complex things clearly and logically. However, I still have some questions. I appreciate if you could further clarify those points.
1. You say in the "Carge Carriers, Understanding the Conduction" that, if there is open circuit the electrons cannot be pushed into the material because of the "Space Charge Neutrality". However, in the "Electrons and Holes", you explain that there are holes at the valence band for electrons to fit in. Then, why don't electrons go into those holes and make the material negatively charged? Note that, these new electrons coming into the material does not need to push any electrons out of the material at the other end because there is enough space (holes) for them to stay.
2. The electrons at the Conduction Band are not connected to an atom, therefore if you push an electron into the material you could squeeze in that electron into the conduction band.
3. How do you explain the "Space Charge Neutrality" (sample of material will always contain the same total amount of charge) when you walk on the carpet and charged with static electricity.
4. Instead of saying "Holes are moving. But this not really happening. They are imagined to be moving at the opposite direction to the electrons which are actually moving", isn't it better to say that "electrons move in the valence band (in addition to the conduction band) too". So the "hole" concept is not necessary to explain that there is also a current in the valence band.
5. In Fig.4, the diagram shows that the hole moves from the middle to the left (the same direction as electrons). However, the description says that it moves to the right.
Thanking in advance for your time to answer these questions.