FREQUENCY SPECTRUM OF GIANT ACOUSTIC WAVE PACKETS GENERATED IN CdS BY HIGH ELECTRIC FIELDS

Zucker, J. E.; Zemon, S.

doi:10.1063/1.1754627

Cited by 81 publications

(10 citation statements)

References 11 publications

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“…The field was applied as single voltage pulses with a repetition rate well below one pulse per second in order to avoid crystal heating. Frequently, at high acoustic flux levels in the crystal, damage similar to that reported by Zucker and Zemon (12) was observed. When this occurred the current waveform was found to change.…”

Section: Methodssupporting

confidence: 68%

Optical modulation by acoustoelectric domains in semiconducting CdS

Kumar

Hutchinson

1970

Radiation Effects

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Section: Methodssupporting

confidence: 68%

Optical modulation by acoustoelectric domains in semiconducting CdS

Kumar

Hutchinson

1970

Radiation Effects

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“…Measurements were carried oVt on semiconducting CdS (p = 30 &2 cm) with the electric field applied along the c-axis (typical dimensionsA = 1 X 1 mm 2, L = 1.5 mm). From the threshold voltage defined by the onset of the current fluctuations [8], Brillouin scattering data and the knee-voltage in the current-voltage characteristic it was clear that transversal off-axis waves were amplified in accordance with earlier reports [9].…”

Section: A[a/(r~+iw)+c1 + A2 + U3~e K1k2l[exp(-ik1l)-exp(-ik2l)]supporting

confidence: 67%

Ac impedance of electro-acoustically active semiconductors

1980

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The ac small-signal impedance ofelectro-acoustically active semiconductors is calculated. Essential for the ac description presented is the introduction of potential troughs that are coupled to the amplified acoustic waves. The calculated impedance shows a frequency dependent behaviour and resonances which are in good agreement with experimental results for CdS.1. Introduction. For many years now continuous interest has been shown in the electro-acoustic effect, i.e. the amplification of travelling acoustic waves through interaction with supersonic drifting charge carriers in piezo-electric semiconductors.As a first step White [1] gave in 1962 a linear description of the electro-acoustic effect known as the linear small-signal gain theory. In 1965 Greebe [2] used the linear small-signal gain theory to calculate the consequences that boundary conditions have on the impedance of semiconducting piezo-electric plates. Strong nonlinear interaction of space charge waves with stress waves, however, restricts the usefulness of linear theories.The most prominent nonlinear effects appearing in the sound amplification process are current saturation, electro-acoustic domain formation, current oscillations, parametric interaction of sound waves, large current fluctuations in the saturation current, and impedance effects. Several authors [3][4][5][6][7]have tried to describe these nonlinear phenomena. Since, however, descriptions of this kind, which start from basic principles, are very difficult, many of these phenomena are not yet understood quantitatively.In 1967 Moore [6] avoided the use of nonlinear equations by suggesting that the observed current saturation and current fluctuations are caused by bunching of free charge carriers in potential troughs which are coupled to the amplified acoustic waves via the piezo-electric effect. He described the observed current fluctuations in CdS by a trough creation-annihilation process.In 1978 Zijistra and Gielen [7] modified this theory by accounting for transit time effects in a local description. They neglected the displacement and the diffusion current in the expression for the current density and assumed that the creation and annihilation of troughs are independent of electric field strength. As a consequence they found a frequency-independent impedance. Experimentally, however, the observed ac impedance of electroacoustically active CdS crystals turned out to be frequency dependent. In fact experimental results showed in addition to the familiar dielectric roll-off, another, lower frequency roll-off in the range of 1 MHz.The aim of this paper is to show that the observed frequency dependence of the ac impedance can be explained if the local description is extended by taking into account diffusion, space charge, displacement current and the electric field dependence of the trough creation and annihilation rates. It should be noted that this calculation holds for crystals where a continuous type of amplified acoustic flux is observed (i.e. where no electro-acoustic domains are o...

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“…This showed that even in the presence of large lattice losses a net gain can still be maintained with a drift velocity of electrons only slightly larger than us. Although in practice acoustic flux domains are not rectangular and contain several frequencies of acoustic waves (Zucker and Zemon 1966), the results of the calculations bring out the essential features of domain growth and current saturation. The actual shape and harmonic content of a domain would of course be very much determined by its origin.…”

Section: Discussionmentioning

confidence: 99%

A Characterization of the Closed Linear Spans of Two Families of Incomplete Systems of Analytic Functions

Džrbašjan¹

1982

Math. USSR Sb.

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A treatment of various acoustoelectric problems, using the large-signal expressions for gain and current saturation which were derived by the authors in an earlier paper, is presented.The phenomena dealt with are : (i) Travelling high-field domains in semiconducting CdS.(ii) Damped and continuous oscillations in photoconductive CdS.(iii) The current-voltage characteristics of thin platelets of photoconductive CdS. The essential characteristics of the above phenomena are obtained in the numerical calculations carried out for specified cases.

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FREQUENCY SPECTRUM OF GIANT ACOUSTIC WAVE PACKETS GENERATED IN CdS BY HIGH ELECTRIC FIELDS

Cited by 81 publications

References 11 publications

Optical modulation by acoustoelectric domains in semiconducting CdS

Optical modulation by acoustoelectric domains in semiconducting CdS

Ac impedance of electro-acoustically active semiconductors

A Characterization of the Closed Linear Spans of Two Families of Incomplete Systems of Analytic Functions

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