Hey guys! I'm researching and writing notes on semi-conductors and how they work. I've learnt about the electron energy profile for conductors, insulators and semi-conductors and have a basic understanding on energy bands of each and how they're put together. I'm having difficulties learning how semi-conductors actually conduct electricity. I've read that they have a small energy gap and therefore, thermal energy, at room temperature, is enough to excite electrons in the valence band and jump them into the conduction band, ready for electricity. However, as they jump over due to enough quantised energy provided, they leave positive 'holes' behind. These 'holes' and the electrons provide current flow. I don't quite understand how the positive holes can provide the current (even though current is the flow of CHARGES), if the band theory is about the energy levels of electrons and what they can exist in when their atoms form a solid, how does valence band conduct current? isn't it just a band of energy levels or does the the band of energy levels refer to the structure of the solid and where the electrons of the solid is placed (i.e in chemical bonds)? Thanks in advance for anyone who helps!