Defect studies in strain-relaxed Si1-xGex alloys

Authors : Şeref KALEM

Pages : 275-282

Doi:10.3906/fiz-1212-1

View : 14 | Download : 4

Publication Date : 0000-00-00

Article Type : Research Paper

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 insert ignore into journalissuearticles values(0.05 \le x \le 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 insert ignore into journalissuearticles values(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 insert ignore into journalissuearticles values(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.
Keywords : Si1 xGex alloys, photoluminescence, Raman light scattering