Dielectric function spectra and phonon modes of highly disordered (AlxGa1 - x)0.48In0.52P, i.e., solid solutions with nearly randomly distributed cations, lattice matched to GaAs, are studied for A1 compositions x = 0, 0.33, 0.48, 0.7, 0.82, and 1 using far-infrared ellipsometry and Raman scattering. An anharmonic oscillator model approach is employed for line-shape analysis of the (AlxGa1 - x)0.48In0.52P dielectric function. A complex phonon mode behavior for the random-alloy solid solutions is found: (i) two (one weak GaP-like and one strong InP-like or one weak InP-like and one strong A1P-like with TO-LO splitting) bands are present in Ga0.52In0.48P and A10.52In0.48P, respectively, (ii) three (one weak GaP-like, one weak A1P-like, and one strong InP-like) bands dominate the quaternary compounds for x < 0.5, (iii) the GaP-like band is absent for x > 0.5, and (iv) three additional modes (AM's) with low polarity occur with small composition dependencies at AM1 ∼ 313 cm-1, AM2 ∼ 351 cm-1, and AM3 ∼ 390-405 cm-1, respectively. Results from polarized Raman measurements agree excellently with the mode scheme developed from the ellipsometry study. Modes AM1 and AM2 coincide with CuPt-type superlattice-ordering-induced lattice modes, predicted recently for Ga0.52In0.48P from first-principles calculations IV. Ozoliņš and A. Zunger, Phys. Rev. B 57, R9404 (1998)] and may be used to identify small degrees of ordering in A1GaInP by far-infrared ellipsometry.
|Original language||English (US)|
|Number of pages||13968551|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Oct 15 2001|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics