Semiconductor Junctions: Electric Fields and Currents

This lecture discusses the behavior of semiconductor junctions, focusing on the depletion zone, electric fields, and current characteristics. It begins with the effects of applying voltage to metal-semiconductor junctions, explaining how negative and positive voltages influence the energy bands and barrier heights. The instructor describes the conditions for equilibrium, where the electric field is zero, and the relationship between charge density and electric field. The lecture further explores the mathematical foundations of electric fields and potentials using Maxwell's equations, leading to the derivation of the depletion width and junction capacitance. The discussion then shifts to current flow in forward and reverse bias conditions, detailing thermal emission and the Richardson constant. The instructor compares different semiconductor materials, such as silicon and gallium arsenide, highlighting their impact on current flow. Finally, the lecture covers the characteristics of Schottky diodes, including conductance and resistance, and introduces the concept of junction capacitance, providing a comprehensive overview of semiconductor device behavior.