Lecture
This lecture covers the properties of extrinsic semiconductors, focusing on impurities and doping effects. It explains the position of the Fermi level, ionization, and neutrality conditions. The impact of impurities in Ge, Si, and GaAs is discussed, highlighting the creation of trap states and recombination centers. The lecture also delves into carrier transport properties, including drift and diffusion, resistivity, and mobility calculations for different semiconductor types. It emphasizes the importance of mobility in determining carrier diffusion length and conductivity. Practical examples and typical values for solar cells are provided, along with the relationship between drift and diffusion currents in semiconductors.