We report on the experimental observation of direct interband-critical-point transitions and phonon modes in BxGa1−xAs alloys (0 < x < 0.03) and their evolution with increasing boron concentration using spectroscopic ellipsometry and Raman scattering. Our results are compared to the corresponding values in the GaNyAs1−y (0 < y < 0.037) material system. For BxGa1−xAs, we obtain only a small bowing coefficient of the Eg(x) dependence in contrast to the giant redshift of the GaNyAs1−y band-gap energy with y. The higher lying interband-transition energies of BxGa1−xAs (E1, E1 + Δ1, E0′, E2, and E1′) are slightly redshifted with increasing boron concentration. A similar behavior is found for the critical points E0′, E2, and E1′ in GaNyAs1−y. In BxGa1−xAs, we observe, as in GaNyAs1−y, a two-mode phonon behavior using Raman scattering. However, from infrared-ellipsometry or -transmission experiments, we can estimate that the oscillator strength or polarity of the BAs-like phonon is at least one order of magnitude smaller than the oscillator strength of the GaN-like phonon measured at a GaNyAs1−y layer with comparable thickness and composition. All results will be explained using a simple model that takes into account the different nature of the chemical bonds in both alloy types.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - May 22 2003|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics