Quasi-conductors are considered to be a special class of chemical elements. People got known about these materials in the end of the 19th century, but only in the 20th century scientists managed to get more knowledge about them. In 1923 Russian physicists proved the ability of utilizing of semiconductor-metal contacts to accelerate the producing of fluctuations. During further years igct were excluded by tubes. The most considerable event in the history of semiconductor devices was the invention of the first transistor by Bell corporation in 1949. The intense research of the characteristics of semiconductors was begun at the same time.

Many physicists carry out a great deal of researches just to gain more knowledge about such characteristic of semiconductors as stimulated radiation. It caused the appearing of semiconductor laser device based on usage of p - n barriers and then on heterojunction.

Today we may see a huge amount of various pulsed power devices which operate with assistance of use of semiconductors. Nowadays it is impossible to carry out any researches without some modern technologies which are founded on use of semiconductors.

The conductivity of semiconductors lies in diapason between conductivity of metals and conductivity of isolators. This feature is caused the division of semiconductors as a detached type. There are several elements which are mainly used to develop the semiconductor devices. They are germanium, selenium, silicon, etc.

Scientists haven't been interested in semiconductors for very long period of time. Abram Ioffe is a Russian scientist that started carrying out different researches in field of semiconductors. He noticed that this amazing type of matter has some unique features and described how they may be utilized. Any semiconductor system has such basic characteristics as electron and hole conduction. The characteristics of semiconductor are related to the conditions they are situated. The admixtures affect considerably on the electron conduction of the semiconductors.

The most important semiconductor systems which are used in technologies are diodes, transistors and thyristors which are based on elements with electron and hole conductions. Semiconductors are widely utilized as their features are useful for almost every electric system. They are used to transform light and heat energy into electricity and vice versa. Several of them are even able to produce cold and heat. Semiconductors perform the main functions in lots of different devices: atomic batteries, quantum generators, processors and even simple radio receivers. Almost every engineer that works in company related to electricity should know how important the voltage sensors are. The usage of semiconductors instead of tube systems permits to lower the sizes and weight of electronic devices. The analogue systems are not equal if we speak about their reliability and power. Tube drops behind.

We can't imagine how the humankind may do without lots of devices that are based on usage of semiconductors.