PN Junctions and Heterostructures: Principles and Applications

This lecture covers the fundamental concepts of pn junctions and heterostructures in semiconductor physics. It begins with an introduction to homojunctions and heterostructures, explaining the significance of space charge regions and doping levels. The instructor discusses the electrical characteristics of pn junctions, including band bending at surfaces and interfaces, and the effects of depletion and inversion layers. The lecture further explores Anderson's rule for band alignments in heterostructures, detailing how different semiconductor materials interact at their interfaces. The concepts of lattice mismatch and strain are also addressed, highlighting their impact on defect density and material properties. The instructor emphasizes the practical applications of these principles in designing solar cells and light-emitting diodes, illustrating how understanding these junctions can lead to advancements in semiconductor technology. The session concludes with a discussion on the implications of applying external biases to pn junctions, reinforcing the importance of these concepts in real-world applications.