minority carrier injection,in electronics, a process taking place at the boundary between p-type and n-type semiconductor materials, used in some types of transistors. Each semiconductor material contains two types of freely moving charges: electrons (negative charges) and holes (positive charges). Electrons are the more abundant, or majority, carrier in n-type materials, holes being the less abundant, or minority, carrier. In p-type materials, however, holes are the majority carrier, and electrons the minority carrier. If a battery is properly connected to the semiconductor material, the p-type material may acquire additional electrons (minority carriers), injected into the p-type material from the n-type material by the flow of electrons from the battery. This is minority carrier injection. As a newly injected electron moves through the p-type material, it is attracted by the oppositely charged holes. Collision between an electron and a hole stops the free motion of both charges. Thus only a fraction of the injected electrons are able to pass completely through the p-type material. In a transistor, those left over are collected by a second piece of n-type materialIt is important in bipolar junction transistors, which are made of two p-n junctions.