A method is presented which allows the determination of the charge carrier concentration and mobility in n-GaP by Rainan spectroscopy of coupled plasmon-phonon modes. The results a m compared with those of electrical measurements.Es wird eine Methode fur die Bestimmung der Konzentration freier Ladungstrager und deren Beweglichkeit in n-GaP mittels Raman-spektroskopischer Messungen gekoppelter Plmmon-PhononModen vorgestellt. Die Ergebnisse werden mit denen elektrischer Messungen verglichen.
Larger hole concentrations and lower mobilities are measured by Raman scattering of p-GaP in comparison with results of Hall and conductivity investigations. The Hall factor which is responsible for the differences can be obtained bv these measurements and is discussed on the basis of a two-band model.
Problems related to the determination of photoelastic coeAicients and deformation potentials of ZnSe are discussed. The dispersion of the photoelastic coeNcients, determined from the intensity of Brillouin scattering from thermal acoustic phonons, is fitted with theoretical expressions containing deformationpotential constants a, b, and d as fitting parameters. The values of these parameters are sho~n to depend on the choice of the effective masses of electrons and holes.Deformation-potential constants are parameters used to define the coupling between uniform strains and electrons of matter. For tetrahedral semiconductors they are given by constants a, b, and d related to the action of hydrostatic pressure, of a shear strain along [100], and of a shear strain along [ill], respectively, on the valence and conduction bands. ' Various methods to calculate the deformationpotential constants have been reviewed by Cardona2 and Blacha, Presting, and Cardona3 who also give their experimental values in a number of crystals.In preceding papers4 5 we have reported resonance effects in the intensity of Brillouin scattering from thermal phonons in ZnSe when the energy of the exciting light, tao, is below the energy of the band gap, E~. Consequently, a theory of resonance Brillouin scattering was derived~b y taking into account both the intraband and the interband transitions between the conduction band, the valence band, and its split-off band (spin-orbit splitting). In Ref. 6 we calculated the values of the deformation potentials from photoelastic coefficients determined at certain laser frequencies. Here we reconsider these data by using best-fitting curves for the frequency dependences of p&. It is also shown that the values of the deformation-potential constants are sensitive to the choice of the reduced masses of electrons and holes.The values of pit(to), pi2(to), and p~(to) measured at different Ar+ and Kr+ laser wavelengths are presented in Fig. I, together with their best fits to Eq. (3). There is a clear resonance enhancementof the absolute values of these coefficients when the energy of the light approaches the band gap. It is also found that pii and pi2 cross at 2.5 eV and p44 changes its sign at E-2.53 eV. These "isotro-I pic points" agree well with those obtained from piezobirefringence measurements7 8 and by observing light scattering from acoustoelectrically amplified acoustic domains. 9
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