Doping in Semiconductors: Energy Band Models

This lecture discusses the effects of doping on semiconductors, focusing on intrinsic and extrinsic types. It begins by reviewing intrinsic semiconductors, where the Fermi energy is centered within the band gap, and the carrier concentration is equal in both the valence and conduction bands. The instructor then explains the process of doping, introducing donor and acceptor atoms to modify the semiconductor's properties. For n-type doping, elements like phosphorus and arsenic are used, which release electrons into the conduction band, raising the Fermi level. Conversely, p-type doping involves elements like boron, which create holes in the valence band. The lecture also covers the periodic table's relevance to doping choices and the energy band diagrams for both n-type and p-type semiconductors. The concept of charge neutrality and the occupation rates of donors and acceptors are discussed, emphasizing that doping primarily affects the position of the Fermi level rather than the intrinsic carrier concentration. The lecture concludes with a summary of the hydraulic model applied to doped semiconductors.