There is a detached type of substances which is named semiconductors. This class was discovered in early 1980's but there were no needed technologies to carry on the further researches. The research of semiconductors was continued just in the 1920's. In 1923 Russian scientists proved the ability of usage of semiconductor-metal contacts to quicken the producing of fluctuations. There was no possibility to create some sophisticated devices as semiconductor assembly. The most significant event in the history of semiconductor devices was the creation of the first transistor by Bell corporation in 1949. Since then many persons all over the world become interested in such kind of matter as semiconductors.

The interest to optical characteristics of semiconductors revived because of research of simulated emission in semiconductors. It caused the appearing of semiconductor laser system based on usage of p - n barriers and then on heterojunction.

Nowadays we can see a huge amount of different asymmetric GTO thyristors which operate with assistance of usage of semiconductors. If there were no semiconductor systems utilized in the newest technologies, we won't have an opportunity to carry out such nice researches that are important for other sciences.

The basic reason why semiconductors are considered to be the detached kind is that they have got a conductivity which is between the conductivities of metals and isolators. Such matters as germanium, silicon, selenium and some others are believed to be semiconductors.

For very long period of time semiconductors haven't got the attention of physicists and engineers. The first man who decided to gain more knowledge about semiconductors was Abram Ioffe - soviet physicist. This genius proposed many methods of use of semiconductors and every up to date system works on these principles. Every semiconductor system has such basic characteristics as electron and hole conduction. Such characteristics may be changed by usage of adding some admixtures or changing temperature. For example, by usage of some admixtures the value of electron conduction may be modified.

Almost every area of newest technologies means use of semiconductors. Diodes, transistors and thyristors are the most often used systems. Semiconductors are broadly used as their characteristics are helpful for almost every electric device. There is an ability to convert almost every type of energy into electric power by mans of semiconductors. Heat and cold can be developed by some kinds of semiconductors. Semiconductor devices can be found in radio receiver and quantum generator, in little atomic battery and in microprocessors. Such devices as fuses are commonly utilized in any construction connected to the electricity. The mass and overall dimensions of semiconductor systems are significantly smaller than their tube variants. The analogue systems are not equal in case we speak about their reliability and power. Tube falls behind.

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