Search

A study is made of the effect of the external field on the amplification of the acoustic waves in semi-conductors. It is found that the amplification occurs for the drift velocity greater than the sound velocity and the carrier drift velocity required to maximize the gain is greatly reduced by the field. Both the geometric and cyclotron resonances are found to occur under the condition of acoustic amplification.
The calculation has shown that the amplification of the acoustic wave in semiconductors depends on the carrier drift velocity which can be altered by the application of the external d.c. fields. The amplification occurs only when the carrier drift velocity exceeds the velocity of sound. In the case of a semiconductor in the presence of an external d.c. electric field only, the frequency (of the long and short wavelength sound wave) at which the maximum gain occurs is controlled by the plasma frequency. The application of crossed d.c. electric and magnetic fields greatly reduces the drift velocity required to maximize the gain.
The geometric resonance in amplification coefficient is associated with the Bessel function in the conductivity tensor. This has to do with the strength of the interaction between the particular orbit and the electric field rather than the resonant absorption/amplification of energy. The results for the. [ABSTRACT FROM AUTHOR]