Quantum Densities and Statistics: Exploring Quantum Well Infrared Photodetectors

This lecture discusses the principles of quantum densities and statistics, focusing on quantum well infrared photodetectors (QWIPs). It begins with an overview of the absorption mechanisms in QWIPs, explaining the role of conduction and valence bands. The instructor elaborates on the tunneling escape process and the significance of selection rules in quantum mechanics. The lecture further explores the density of states in three-dimensional systems, transitioning to two-dimensional and one-dimensional cases, highlighting the differences in quantization. The instructor emphasizes the importance of understanding how energy states are occupied and how this relates to the design of photodetectors. The discussion includes practical applications of QWIPs in infrared detection, detailing how variations in layer thickness can affect the absorption wavelength. The lecture concludes with exercises on calculating densities of states and the statistical mechanics involved in photon and electron states, providing a comprehensive understanding of quantum statistical behavior in various dimensions.