Deformation-potential scattering

For lattice acoustic-mode deformation potential scattering, s =, giving r = /8 = 1.18. For ionized-impurity scattering, s = —f, giving rn0 = 315 /512 = 1.93. For a mixture of independent scattering processes we must... 

W. Richter, Resonant Raman Scattering in Semiconductors Electric Susceptibility. Light Scattering. Experimental Method.s. One-Phonon Deformation Potential Scattering. Infrared Active LO Phonons. Multiphonon Scattering. Conclusions. List of Symbols. References. Subject Index. 

A special situation is found in materials with no LO modes, such as liquefied rare gases. Here deformation potential scattering is the dominant vibronic scattering channel at small energies. 

The mobility of quasi-free electrons has recently been explained by the deformation potential theory. Originally from solid-state physics, this theory was applied by Basak and Cohen [68] to liquid argon. The theory assumes that scattering occurs when the electron encounters a change or fluctuation in the local density which results in a potential change. The potential is assumed to be given in terms of dFo/dfV, d Fo/dfV, etc. The formula they derived for the mobility is ... 

Silicon (Si). The electronic transport is due exclusively to electrons in the [100] conduction band minima and holes in the two uppermost (heavy and light) valence bands. In samples with impurity concentrations below 10 cm , the mobilities are determined by pure lattice scattering down to temperatures of about 10 K (n-type) or 50 K (p-type), for electrons and holes, respectively. Higher impurity concentrations lead to deviations from the lattice mobility at corresponding higher temperatures. For electrons, the lattice mobility below 50 K is dominated by deformation-potential coupling... 

Fig. 3 The drift velocity V against applied field E for electrons undergoing Cerenkov scattering by acoustic phonons. The dashed lines shoi the low field mobilities. The curve 30 is the usual ShocQcley 30 solution. nie curve 10 is the Shockley solution in 10. The two cixrves 130 apply udien the electron is 10 and the phonons axe 30. // and 1 refer to the type of deformation potential.

In region (1), the electron can be considered as quasifree. (An electron is regarded as completely free only in the vacuum.) The structure of the fluid is unperturbed by the presence of the excess electron. The wave function is extended. The basic electron/liquid interaction may be treated as single scattering of an electron on a molecule or atom modified by the structure factor of the liquid, S(q) (Lekner, 1967), or it is considered as multiple scattering off density fluctuations in the framework of the deformation potential theory (Basak and Cohen, 1979). 

The last fact was not taken into account when deriving Equation 4.55. Typical room-temperature values of D+, which are in the range 1-2 x 10 m s", are in agreement with Equation 4.55 if we take into account measured elastic constants, the ratio w+/We ( T5), and the deformation-potential constant ej. From a comparison of Equations 4.55 and 4.58, it follows that the phonon scattering is higher than the electron scattering at all temperatures, with the possible exception of very low temperatures, where T/To 1. However, at these temperatures, is limited by residual impurities, even in the purest metals available. 

The relaxation time rph for positron scattering off phonons can be calculated using the deformation potential approximation [126]... 

The optical phonon spectrum is one of the most fundamental characteristics of the crystals. It reflects the specific features of the interatomic interactions and gives very comprehensive and detailed information about the thermal and optical properties involving the efficiency of the optoelectronic devices. The vibrational properties in all the nitride systems have heen investigated in detail over the years by Raman scattering (RS) spectroscopy. Recent studies of nonpolar a-plane GaN by RS confirmed the finding in the c-plane GaN [107, 108]. However, in some cases there is a lack of agreement between the values of some phonon deformation potentials and strain-free phonon-mode positions in GaN and AlN, as determined theoretically and by employing RS spectroscopy. The nonpolar materials allow an access to the complete set of phonons by infrared spectroscopic ellipsometry (IRSE). This provides an alternative tool to study the vihrational properties and to establish very important and useful fundamental parameters of the nitrides. 

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