Kerääntymiskerros

Kerääntymiskerros, a Finnish term, translates to "accumulation layer" or "accumulation region" in English. It is a concept primarily used in semiconductor physics, particularly when discussing the behavior of charge carriers at the interface between a semiconductor and an insulator or another semiconductor.

In a p-type semiconductor, an accumulation layer is formed when the semiconductor surface is brought into contact with a material that causes majority carriers (holes in a p-type material) to accumulate near the surface. This typically happens when a positive voltage is applied to a metal electrode placed on top of an insulator, which is in turn in contact with the p-type semiconductor. The positive charge on the metal attracts holes to the surface, increasing their concentration above the normal doping level. This region of increased hole concentration is the accumulation layer.

Conversely, in an n-type semiconductor, an accumulation layer is formed when majority carriers (electrons in an n-type material) accumulate near the surface. This occurs when a negative voltage is applied to a metal electrode. The negative charge on the metal attracts electrons to the surface, creating a region with a higher electron concentration.

The formation of an accumulation layer is a fundamental aspect of the operation of many semiconductor devices, including Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs). Understanding and controlling the accumulation layer is crucial for designing and optimizing the performance of these devices. The thickness and conductivity of the accumulation layer depend on factors such as the applied voltage, the doping concentration of the semiconductor, and the properties of the interface.