Diffuosiokerroksen

Diffuusiokerros, often translated as diffusion layer or depletion region, is a fundamental concept in semiconductor physics and devices. It refers to a region within a semiconductor material where mobile charge carriers, such as electrons and holes, have been depleted or removed due to an applied electric field or the formation of a junction.

This depletion occurs when two different types of semiconductor materials, typically p-type and n-type, are brought into contact, forming a p-n junction. At the interface, free electrons from the n-type material diffuse into the p-type material and combine with holes, while holes from the p-type material diffuse into the n-type material and combine with electrons. This recombination process leaves behind immobile ionized donor atoms in the n-type region and immobile ionized acceptor atoms in the p-type region. These fixed charges create an internal electric field.

This internal electric field opposes further diffusion of charge carriers, establishing an equilibrium. The region containing these fixed charges and depleted of mobile carriers is the diffuusiokerros. The width of the diffuusiokerros is crucial for the operation of semiconductor devices like diodes and transistors. A larger applied reverse bias across a p-n junction widens the diffuusiokerros, while a forward bias narrows it. This ability to control the width of the diffuusiokerros is key to rectifying and amplifying properties of semiconductor devices.