Electric current in semiconductors - a directional movement of electrons and holes, which has an effect on the electric field.
a result of experiments, it was observed that an electric current in the semiconductor is not accompanied by the transfer of matter - they do not involve any chemical changes.Thus, the current carriers in semiconductors can be regarded as electrons.
ability of a material to form an electric current in it can be determined by the specific conductivity.According to this indicator conductors occupy an intermediate position between conductors and insulators.Semiconductors - are various types of minerals, certain metals, metal sulfides, etc.Electric current in semiconductors arises from the concentration of free electrons which can move directionally in a substance.Comparing metals and conductors may be noted that there is a difference between the temperature influence on their conductivity.An increase in temperature leads to a decrease in the conductivity of metals.We measure the conductivity of semiconductors increases.If you increase the temperature of the semiconductor, the motion of free electrons will be more chaotic.This is due to an increase in the number of collisions.However, in semiconductors in comparison with metals, significantly elevating the concentration of free electrons.These factors have the opposite effect on the conductivity: the more collisions, the smaller the conductivity, the higher the concentration, the higher it is.In metals, there is no dependence between the temperature and the concentration of free electrons, so that a change in conductivity with increasing temperature decreases only an orderly movement of free electrons.As for semiconductors, the effect of increasing the concentration index higher.Thus, the greater the temperature rise, the greater the conductivity.
There is a relationship between the movement of charge carriers and a term such as an electric current in semiconductors.In semiconductors, the charge carriers is characterized by the appearance of a variety of factors, among which are particularly important are the temperature and the purity of the material.As semiconductors are divided into purity and impurity own.
As for the conductor, the effect of impurities at a certain temperature can not be considered essential for them.Since the semiconductor band gap is small, in an intrinsic semiconductor, when the temperature reaches absolute zero, there is a complete filling of the valence electrons.However, the conduction band is completely free: there is no electrical conductivity, and it functions as a perfect insulator.At other temperatures, there is a possibility that the thermal fluctuations of certain electrons can overcome the potential barrier and appear in the conduction band.
Thomson effect
principle thermoelectric Thomson effect when an electric current in semiconductors, along which there is a temperature gradient in them than the Joule heat would be liberated or absorbed additional amounts of heat depending on which direction the current will flow.
enough uniform heating of the sample having a uniform structure that affects its properties, whereby the material becomes non-uniform.Thus, the phenomenon is specific Thomson Peltier.The only difference is that not different chemical composition of the sample, and the originality of the temperature causes this heterogeneity.
