Amplification of Sound by Hot Electrons

It is well known that sound waves can be amplified in a solid by electrons or holes having a drift velocity, in the propagation direction, greater than the velocity of At least at low temperatures, an electric field strong enough to induce a drift velocity of this magnitude, in a semiconductor, can result in a “hot electron” state.
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The purpose of the present communication is to show that the properties of hot electrons can themselves give rise to a distinct contribution to the amplification, one which does not change sign according as the drift velocity is greater or less than the velocity of sound, both for semiconductors typified by cadmium sulphide
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and those typified by n-germanium.