Explain why does conductivity of germanium crystals increase on doping with galium?
On doping germaniurn with galium some of the positions of lattice of germanium are occupied be galium. Galium atom has only three valence electrons. Therefore, fourth valency of nearby germanium atom is not satisfied and the place remains vacant.
This plac eis deficient of electrons and is therefore called electron hole or electron vacancy. Electron trom neighbouring atom comesandfills the hole, thereby creating a hole in its original position.
Under the influence of electric field electrons move towards positively charged plates through these and conduct electricity. The holes appear to move towards negatively charged plates.
