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.

Nowadays we may see a great deal of different power semiconductor devices that operate with help of usage of semiconductors. Semiconductor substances have been researched for not so long but radio electronics and many other sciences can't do without utilizing of them.

Semiconductors are a broad class of matters which are characterized by the value of conductivity which lies between the conductivities of metals and isolators. Such matters as germanium, silicon, selenium and some others are believed to be semiconductors.

Scientists haven't been interested in semiconductors for quite a long period of time. The first person that decided to gain more knowledge about semiconductors was Abram Ioffe - Russian scientist. He found that this wonderful sort of substance has got some special characteristics and described how they may be utilized. Any semiconductor device has got such basic characteristics as electron and hole conduction. These features can be modified by usage of adding some admixtures or modifying temperature. The admixtures affect considerably on the electron conduction of the semiconductors.

The most significant semiconductor devices that are utilized in technologies are diodes, transistors and thyristors which are founded on materials with electron and hole conductions. Semiconductors are broadly utilized as their features are useful for almost every electronic system. There is a possibility to transform almost every type of energy into electric power by usage of semiconductors. With usage of electricity they can develop heat and cold. Semiconductor systems can be used in radio receiver and quantum generator, in small atomic battery and in microprocessors. Such systems as voltage sensors are commonly utilized in any construction connected to the electricity. If we match devices equipped with semiconductors and tube devices we can see that semiconductors are significantly smaller and lighter. When semiconductors are used some important characteristics as power and reliability are being improved much.

From day to day we may hear about some modern systems that assist people to have more conveniences or even save the lives.