Ridley–Watkins–Hilsum theory

The Gunn effect [ gʌn - ] is a physical effect that occurs in high electric field strengths, in some semiconductor materials and a negative differential resistance effected.

The effect was discovered in 1963 by John Battiscombe Gunn when he contacted barrier -free gallium arsenide ( GaAs) or indium phosphide, finished with high electric field strengths, and from a critical value noticed a very high frequency oscillation in the measured electrical current. This effect was already predicted by BK Ridley, TB Watkins and C. Hilsum, and is therefore also called RWH mechanism. H. Kromer declared him as an electron transfer process.

Is applied, the effect in the Gunn diode to generate microwaves.

Description

Thus, the Gunn effect can occur in a semiconductor, has one of the responsible for the management of electric power energy bands a relative minimum ( electron transport ) or maximum ( hole transport ) have whose energy differs only slightly from the absolute minimum or maximum.

Electrons that have been excited, for example from the valence band to the conduction band, are first in the absolute minimum of the conduction band. This causes the current flow through the semiconductor with increasing first voltage increases. Achievement of these electrons in an electric field an energy that is within the energy difference between absolute and relative minimum ( 0.29 eV for GaAs ), as they are scattered in interaction with optical phonons in the relative minimum. Because the effective mass of the electrons is inversely proportional to the curvature of the band, the electrons in the valley have an increased effective mass and thus a lower average mobility. Therefore, the current decreases as the voltage increases again, ie, it represents a negative differential resistance.