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Defect Characterization in SiGe/SOI Epitaxial Semiconductors by Positron Annihilation.

Ferragut R, Calloni A, Dupasquier A, Isella G - Nanoscale Res Lett (2010)

Bottom Line: The chemical analysis indicates that the interface does not contain defects, but only strongly localized charged centers.In order to promote the relaxation, the samples have been submitted to a post-growth annealing treatment in vacuum.After this treatment, it was possible to observe the modifications of the defect structure of the relaxed film.

View Article: PubMed Central - HTML - PubMed

Affiliation: L-NESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100 Como, Italy.

ABSTRACT
The potential of positron annihilation spectroscopy (PAS) for defect characterization at the atomic scale in semiconductors has been demonstrated in thin multilayer structures of SiGe (50 nm) grown on UTB (ultra-thin body) SOI (silicon-on-insulator). A slow positron beam was used to probe the defect profile. The SiO(2)/Si interface in the UTB-SOI was well characterized, and a good estimation of its depth has been obtained. The chemical analysis indicates that the interface does not contain defects, but only strongly localized charged centers. In order to promote the relaxation, the samples have been submitted to a post-growth annealing treatment in vacuum. After this treatment, it was possible to observe the modifications of the defect structure of the relaxed film. Chemical analysis of the SiGe layers suggests a prevalent trapping site surrounded by germanium atoms, presumably Si vacancies associated with misfit dislocations and threading dislocations in the SiGe films.

No MeSH data available.


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S parameter as a function of the mean implantation depth: SiGe a “as grown” (full symbols); SiGe b annealed (open symbols). Continuous and dashes lines are VEPFIT simulations, while vertical dashed lines mark the position of interfaces (after Ref. [2])
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Figure 3: S parameter as a function of the mean implantation depth: SiGe a “as grown” (full symbols); SiGe b annealed (open symbols). Continuous and dashes lines are VEPFIT simulations, while vertical dashed lines mark the position of interfaces (after Ref. [2])

Mentions: Figure 3 shows the experimental S parameter profiles of the SiGe/SOI samples listed in Table 1. The approximated mean implantation depth was calculated according to Eq. 1 (the density of the SiGe layer has been estimated to be 3.52 g/cm3). The results indicate the existence of a wide plateau up to ~50 nm in both samples, which corresponds to the SiGe layer, and changes in height appear after the thermal treatment. Given the mixing between the signals coming from the oxide and from the SiGe/Si layers, changes in the surface layers morphology can be appreciated by comparing the two S parameter evolutions relative to the sample before and after structural relaxation due to the annealing step. The increase of the S parameter at low implantation energy can be thus directly related to an enhanced interaction with free electrons. The exact positioning of the defected region is behind the resolution limits of the current measurements, given that the positron diffusion length in intrinsic semiconductors can be as high as 240 nm [12].


Defect Characterization in SiGe/SOI Epitaxial Semiconductors by Positron Annihilation.

Ferragut R, Calloni A, Dupasquier A, Isella G - Nanoscale Res Lett (2010)

S parameter as a function of the mean implantation depth: SiGe a “as grown” (full symbols); SiGe b annealed (open symbols). Continuous and dashes lines are VEPFIT simulations, while vertical dashed lines mark the position of interfaces (after Ref. [2])
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2991171&req=5

Figure 3: S parameter as a function of the mean implantation depth: SiGe a “as grown” (full symbols); SiGe b annealed (open symbols). Continuous and dashes lines are VEPFIT simulations, while vertical dashed lines mark the position of interfaces (after Ref. [2])
Mentions: Figure 3 shows the experimental S parameter profiles of the SiGe/SOI samples listed in Table 1. The approximated mean implantation depth was calculated according to Eq. 1 (the density of the SiGe layer has been estimated to be 3.52 g/cm3). The results indicate the existence of a wide plateau up to ~50 nm in both samples, which corresponds to the SiGe layer, and changes in height appear after the thermal treatment. Given the mixing between the signals coming from the oxide and from the SiGe/Si layers, changes in the surface layers morphology can be appreciated by comparing the two S parameter evolutions relative to the sample before and after structural relaxation due to the annealing step. The increase of the S parameter at low implantation energy can be thus directly related to an enhanced interaction with free electrons. The exact positioning of the defected region is behind the resolution limits of the current measurements, given that the positron diffusion length in intrinsic semiconductors can be as high as 240 nm [12].

Bottom Line: The chemical analysis indicates that the interface does not contain defects, but only strongly localized charged centers.In order to promote the relaxation, the samples have been submitted to a post-growth annealing treatment in vacuum.After this treatment, it was possible to observe the modifications of the defect structure of the relaxed film.

View Article: PubMed Central - HTML - PubMed

Affiliation: L-NESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100 Como, Italy.

ABSTRACT
The potential of positron annihilation spectroscopy (PAS) for defect characterization at the atomic scale in semiconductors has been demonstrated in thin multilayer structures of SiGe (50 nm) grown on UTB (ultra-thin body) SOI (silicon-on-insulator). A slow positron beam was used to probe the defect profile. The SiO(2)/Si interface in the UTB-SOI was well characterized, and a good estimation of its depth has been obtained. The chemical analysis indicates that the interface does not contain defects, but only strongly localized charged centers. In order to promote the relaxation, the samples have been submitted to a post-growth annealing treatment in vacuum. After this treatment, it was possible to observe the modifications of the defect structure of the relaxed film. Chemical analysis of the SiGe layers suggests a prevalent trapping site surrounded by germanium atoms, presumably Si vacancies associated with misfit dislocations and threading dislocations in the SiGe films.

No MeSH data available.


Related in: MedlinePlus