Quasi-conductors are considered to be a unique class of chemical elements. Scientists got known about these materials in the end of the 19th century, but just in the 20th century scientists managed to get more knowledge about them. The first successful experiment was performed by the Russian scientists in 1923. They proved that semiconductors can be utilized to generate fluctuations. During several years semiconductor assembly were excluded by tubes. Only in the beginning of the 50's with the invention of transistors in 1949 the wide usage of crystal detectors began. The intense research of the features of semiconductors was begun at the same time.

The concern to optical features 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.

Today we may see a great deal of different power semiconductor devices that work with help of usage of semiconductors. Semiconductor matters have been studying for not so long but radio electronics and lots of other sciences can't do without utilizing of them.

Semiconductors are a wide class of matters that are characterized by the value of conductivity which is situated between the conductivities of metals and isolators. There are some elements that are mainly used to develop the semiconductor devices. They are germanium, selenium, silicon, etc.

It sounds a bit strange but physicists didn't want to carry out researches of semiconductors for a long time. Abram Ioffe is a Russian physicist who began performing various researches in field of semiconductors. This genius offered some methods of usage of semiconductors and every modern device works on these principles. Every semiconductor system has such basic characteristics as electron and hole conduction. It is related to the chemical composition of the used admixtures. The admixtures affect significantly on the electron conduction of the semiconductors.

Almost every area of modern technologies implies usage of semiconductors. Diodes, transistors and thyristors are the most often used systems. Semiconductors are broadly used as their features are useful for almost every electric device. There are systems based on semiconductors that may turn light and heat energy into electricity and vice versa. With usage of electric power they may create heat and cold. Such systems as radio receivers, atomic batteries, quantum generator, microprocessors etc comprise semiconductors. Engineers can't do without semiconductor rectifiers, changers, power resistors and amplifiers. The use of semiconductors instead of tube systems allows to lower the overall dimensions and masses of electronic devices. The analogue systems are not equal in case we talk about their reliability and power. Tube drops behind.

Day after day we may hear about some modern inventions which help people to have more conveniences or even save the life.