Abstract
Raman light scattering, low-temperature photoluminescence, light-scattering tomography, and hydrogenation were used to investigate optical properties of defects in strain-relaxed Si1-xGex (0.05 ≤ x ≤ 0.50) alloys. The photoluminescence emission was characterized by typical zero-phonon, phonon-assisted, and dislocations-related emissions, which are dependent on Ge composition x. However, luminescence spectra exhibited above band-gap features, which are likely associated with the presence of Si-rich regions in the alloys. The results are correlated with light-scattering tomography, revealing the presence of dislocations and Si precipitates. The excess peak at 519 cm-1 in Ge-rich samples is supportive of this observation. At low Ge content, a dislocation-related band (D2 line) at 14,204 Å dominates D-band emission for x < 0.25 while overall D-band emission intensity decreases with x. Hydrogenation was found to enhance D-band emission, indicating a passivation of nonradiative recombination centers inside dislocation cores. Si-Si, Si-Ge, and Ge-Ge phonons (TO, TA, and LA),which are participating in luminescence emission, evolve with increasing Ge content and Ge-Ge and Si-Ge TO lines dominate the Raman spectrum to the detriment of the Si-Si TO phonon line. Raman spectra reveal the presence of alloy fluctuations and possible presence of Ge particles, particularly in Ge-rich samples.
Original language | English |
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Pages (from-to) | 275-282 |
Number of pages | 8 |
Journal | Turkish Journal of Physics |
Volume | 37 |
Issue number | 3 |
DOIs | |
Publication status | Published - Nov 2013 |
Externally published | Yes |
Keywords
- Photoluminescence
- Raman light scattering
- Si Ge alloys