The fractional effect is small fluctuations of the magnitude of the electric current from the average value caused by the uneven diffusion of current carriers in semiconductors or the uneven emission of electrons from the cathode in vacuum devices .
The shot effect was predicted by Walter Schottky in 1918 .
When current flows in semiconductors, charge carriers experience a large number of collisions with atoms and other carriers inside the cathode, as a result of which the magnitude and direction of the speed of an individual carrier when flying through any section of the semiconductor may be different. This leads to the fact that the number of carriers that have passed through the cross section over identical small periods of time is different, as a result of which the current experiences random deviations from its mean value (fluctuations).
The term “shot effect” (as well as shot noise ) arose due to the fact that due to it an acoustic noise appears in the loudspeaker connected to the output of the amplifier or radio receiver, resembling the noise of spilling pellets.