Understanding Ohmic Contacts: Schottky and Avalanche Effects

This lecture discusses the principles of ohmic contacts in semiconductor devices, focusing on the Schottky effect, avalanche effect, and tunnel effect. It begins by explaining the ideal currents in a semiconductor metal diode and the behavior of the diode under different polarizations. The instructor describes how the Schottky effect leads to a decrease in the barrier when the surface charge increases, resulting in a current that rises with negative tension. The avalanche effect is introduced, highlighting how a strong electric field can accelerate electrons, leading to an increase in current at breakdown tension. The tunnel effect is also explained, emphasizing how a thin energy barrier allows electrons to cross without resistance. The lecture concludes with a summary of the importance of ohmic contacts in CMOS structures, detailing how high doping levels prevent diode effects and ensure efficient current flow. The distinctions between ohmic contacts and Schottky junctions are clarified, providing a comprehensive understanding of their roles in semiconductor technology.