Acoustoelectric Effect inn-Type Germanium

Abstract

Theory and experiment are presented for the drag exerted on electrons in a solid by a traveling ultrasonic wave. After a discussion of the reasons why the effect is generally very small, it is shown that under certain conditions in w-type germanium it may be quite appreciable, and that its size directly indicates the intervalley scattering rate. Experimental data are given for arsenicdoped germanium ranging in impurity content from 10 14 to 10 16 cm -3 , at temperatures from 20 to 160°K. These yield the absolute value of the "uniaxial" deformation potential constant (16 ev) and the intervalley scattering rate as a function of temperature and doping. The interpretation of the results ascribes intervalley scattering action both to phonons and to impurities. The phonon contribution yields the frequency of the (100) longitudinal phonon (6.6X 10 12 sec" 1 ) and the size of the appropriate coupling parameter ; the impurity contribution yields intervalley scattering cross sections for neutral and ionized donors as a function of temperature. The two cross sections are explained as, respectively, being due to exchange scattering events and to compound capture-reemission processes. Further analysis gives a lower limit to the valley-orbit splitting of the arsenic donor ground state (1.7X10 -3 ev). The experiment verifies that the conduction-band valleys lie on (111) axes at the Brillouin zone edge. Ultrasonic attenuation due to intervalley scattering is discussed and is shown to be too small to be easily measurable.

Detection and Measurement of Acoustic Fields

“…A so-called acousto-electric effect can arise as a result of coupling of the energy of an acoustic travelling wave to the system of photo-excited charge carriers within a photosensitive semiconductor crystal such as cadmium sulphide (Weinreich et al 1959). The effect is a consequence of the finite time-lag that exists between the wave and the response of the charge carriers, which are dragged along with the wave, similarly to electrons in a linear accelerator, and gives rise to a unidirectional potential gradient.…”

Galvanomagnetic effects in many‐valley semiconductors for strong magnetic and heating electric fields

“…The inter-valley redistribution decreases because a t high heatings for 2 > k o the inter-valley scattering time as function of mean energy becomes more gradual (see e.g. [8] where the inter-valley scattering time versus temperature is represented).…”

Analysis of a Circular Piezoelectric Semiconductor Embedded in a Piezoelectric Semiconductor Substrate

“…When the crystal is also semiconducting, the electric field produces currents and space charge resulting in dispersion and acoustic loss [2]. The interaction between a traveling acoustic wave and mobile charges in piezoelectric semiconductors is called the acoustoelectric effect which is a special case of a more general phenomenon which may be called wave-particle drag [3]. It has also been found that an acoustic wave traveling in a piezoelectric semiconductor can be amplified by the application of a dc electric field [4].…”