There is a detached class of substances which is named semiconductors. Scientists got known about these substances in the end of the 19th century, but only in the 20th century scientists managed to obtain more knowledge about them. In 1923 Russian physicists proved the ability of utilizing of semiconductor-metal contacts to accelerate the generation of fluctuations. But such devices as semiconductor assembly which are utilized nowadays were created considerably later. First transistor was created in Bell's laboratory in 1949. This event influenced the fast development of semiconductor devices. Since then a lot of people all over the world become interested in such kind of matter as semiconductors.
The concern to optical characteristics of semiconductors revived because of research of induced emission in semiconductors. By means of such principles as p - n barriers and heterojunction physicists managed to create laser device in the beginning of the 60's.
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