A hole is a missing electron in an otherwise filled valence bond, treated as a mobile particle carrying positive charge . It is not a real particle — it is the absence of an electron — but it moves, carries current, and is bookkept exactly like a positive charge, so we treat it as one.
Where holes come from
In a silicon crystal every atom shares its four valence electrons in covalent bonds. When thermal energy (or light, or a dopant) removes one electron from a bond — promoting it to the conduction band — the bond is left with a vacancy. That vacancy is the hole. Because creating a free electron always leaves a hole behind, holes and electrons appear together as electron–hole pairs, and they disappear together when a free electron drops back into a vacant bond (recombination).
Why a hole moves and acts positive
The hole itself does not move — electrons move. But a neighbouring bound valence electron can hop into the vacancy without needing to be freed into the conduction band. When it does, the bond it filled is now complete, but the bond it left is now empty: the vacancy has shifted one site over, in the direction opposite to the electron’s hop.
Repeat this many times and the vacancy travels through the crystal by successive electron hops between bonds. The net result is a flow of positive charge in the direction of vacancy motion. Rather than track the complicated cooperative motion of many bound valence electrons, we package it into one fictitious particle — the hole — with charge that drifts and diffuses just like a real carrier. This is enormously simpler and is exactly how semiconductor analysis treats it.
Holes as charge carriers
A doped semiconductor conducts via two carrier types in parallel: free electrons (charge ) and holes (charge ). In an n-type material electrons vastly outnumber holes; in a p-type material holes are the majority carrier. Their concentrations are linked by the Mass-action law . The two carrier types responding oppositely to an electric field — electrons drifting one way, holes the other, both contributing current in the same direction — is the foundation of how a PN junction, and therefore every diode and transistor, works.