Piezospectroscopic determination of the ratio of the electron-phonon to hole-phonon scattering matrix elements for LA and TA phonons in GaP

An investigation of the stress dependence of the amplitude of the normalized wavelength-modulated absorption spectra of the phonon-assisted (LA, TA, and TO) indirect transition in GaP at 77 K has been performed. Theoretical expressions, which include the stress-dependent mixing between the top of the valence band (Γ8,v) and its spin-orbit splitoff band (Γ7,v) have been calculated for the intensities of the allowed phonon-assisted (LA, TA, TO, and LO) transitions. From the experimental results for →X∥[111] and →X∥[001], and the above theoretical expressions, the ratio of the electron-phonon (e-ph) to hole-phonon (h-ph) scattering matrix elements has been obtained for the LA and TA phonons. For the LA phonon the ratio was found to be S_e-phLAS_h-phLA=0.6 and for the TA phonon S_e-phTAS_h-phTA=1.1.