AN INVESTIGATION ON THE THERMAL-STABILITY OF THE GEXSI1-X SI SUPERLATTICE GROWN BY MBE/

Strained GexSi1-x/Si superlattices with Ge content of 0.48 and 0.49 gr own by MBE at 420-degrees-C (sample A) and 570-degrees-C (sample B) we re annealed and studied by X-ray diffraction, Raman scattering and TEM . The cross section TEM image of the samples before annealing showed t hat the growth of sample A was two-dimensional, but for sample B, the growth of the GexSi1-x layer was three-dimensional. By the X-ray diffr action spectra before and after annealing for samples A and B, the str ain relaxations from X-ray diffraction measurements were 27% and 35% f or samples A and B, respectively. This difference might be from the th ree-dimensional growth of sample B, in which the strain was stronger t han that in sample A. Raman scattering measurements showed that the Ge -Ge peak and the Ge-Si peak shifted towards the lower energy after ann ealing, while the Si-Si peak shifted towards the higher energy. The re ason for the shift of these peaks could be explained by the common con tribution of the strain relaxation and the internal diffusion of Ge at oms into the Si layer. In addition, the behavior of the strained GexSi 1-x/Si superlattice annealed by rapid thermal annealing technology was also studied. A sample of superlattice with a Ge content of 0.46 was rapidly thermal annealed at the temperature range of 600 to 1000-degre es-C and at each temperature the sample was annealed twice for 40 s ea ch time. From X-ray diffraction measurements it could be found that as the annealing temperature increased from 600 to 900-degrees-C, the st rain relaxation would increase from 19% up to 57%. As the sample was a nnealed at 1000-degrees-C, no satellite peaks were in the X-ray diffra ction spectra and no multilayer structure could be observed in the cro ss section TEM image, that is, in the sample the GeSi layers were comp letely mixed up with the Si layers.