Continuity Equations in Semiconductor Physics

This lecture discusses the continuity equations relevant to semiconductor physics, focusing on charge conservation and the behavior of charge carriers. The instructor begins by reviewing the Maxwell equation and the concepts of drift and diffusion currents, as well as generation and recombination processes. The lecture introduces the continuity equations that govern the variation of electron and hole concentrations in a semiconductor. It emphasizes the importance of understanding how charge variations occur due to generation, recombination, and current flow. The instructor elaborates on the mathematical formulation of these concepts, including the divergence of current and its relation to charge conservation. The discussion extends to calculating carrier concentrations out of equilibrium, introducing quasi-Fermi levels and their significance in determining carrier densities. The lecture concludes by highlighting the advantages of using quasi-Fermi levels in analyzing semiconductor behavior, particularly in non-equilibrium conditions, and their role in simplifying the understanding of current flow in semiconductor devices.