Formation of Bands in Semiconductors: Energy States and Stability

This lecture discusses the formation of energy bands in semiconductors, focusing on the behavior of atoms and molecules in crystalline structures. The instructor begins by examining an atom with three electrons across two energy levels, illustrating how to draw the energy diagram for a cell containing two such atoms. The concepts of bonding and antibonding states are introduced, explaining how these states influence the stability of molecules like H2 and Li2. The lecture further explores the formation of bands in silicon, detailing how covalent bonds create a band structure. The instructor explains the significance of valence and conduction bands, emphasizing the role of temperature in electron transitions. The discussion includes the metallic nature of lithium and beryllium, highlighting how their energy states lead to metallic bonding. The lecture concludes with a comprehensive overview of how these principles apply to various semiconductor materials, providing a foundational understanding of their electronic properties and behaviors in solid-state physics.