Antimony diffusion in silicon-germanium alloys
Antimony diffusion in silicon-germanium alloys
The objective of this work was to study the diffusion of antimony in silicon-germanium alloys which are of great commercial interest because of their potential for fabricating higher performance devices such as heterojunction bipolar transistors and heterojunction field effect transistors.
Knowledge of the diffusion of antimony will give fundamental material information about point defect species and populations in the alloy system and silicon itself. This work represents a fundamental materials study on the nature of diffusion in this system.
The work comprises of furnace anneals of silicon/silicon-germanium heterostructures grown by MBE to incorporate buried antimony delta-layers. Antimony concentration was measured using Secondary Ion Mass Spectrometry (SIMS) and a method for determining diffusivities from SIMS measurements of ultra-fine layers is introduced.
This work constitutes the first ever measurement of antimony diffusivities in silicon-germanium alloys. Diffusitivies ranged from 4.63x10-18 cm2/s in Si0.9Ge0.1 to 1.61x10-17cm2/s in Si0.7Ge0.3 measured at 800oC: successively higher than the antimony diffusivity in silicon. These results are consistent with later studies.
The results of a diffusivity vs. time study and a diffusivity vs. silicon-germanium composition study are included. Equilibrium antimony diffusion coefficients in alloys of up to 30% germanium are presented along with a possible transient effect. Changes in antimony diffusivity are attributed to changes in the vacancy population and the vacancy enthalpy of migration.
Comparisons with the diffusivity of boron vs. germanium content in silicon-germanium alloys lead to the proposal that, in silicon rich alloys, boron diffuses predominantly via the interstitialcy mechanism. The dependence of diffusivity on germanium content for boron is different to that of antimony and it is proposed that the boron diffusion mechanism changes from largely interstitialcy in silicon to vacancy in germanium - the change occurring at round 40% germanium.
University of Southampton
Paine, Andrew David Nicholas
1998
Paine, Andrew David Nicholas
Paine, Andrew David Nicholas
(1998)
Antimony diffusion in silicon-germanium alloys.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The objective of this work was to study the diffusion of antimony in silicon-germanium alloys which are of great commercial interest because of their potential for fabricating higher performance devices such as heterojunction bipolar transistors and heterojunction field effect transistors.
Knowledge of the diffusion of antimony will give fundamental material information about point defect species and populations in the alloy system and silicon itself. This work represents a fundamental materials study on the nature of diffusion in this system.
The work comprises of furnace anneals of silicon/silicon-germanium heterostructures grown by MBE to incorporate buried antimony delta-layers. Antimony concentration was measured using Secondary Ion Mass Spectrometry (SIMS) and a method for determining diffusivities from SIMS measurements of ultra-fine layers is introduced.
This work constitutes the first ever measurement of antimony diffusivities in silicon-germanium alloys. Diffusitivies ranged from 4.63x10-18 cm2/s in Si0.9Ge0.1 to 1.61x10-17cm2/s in Si0.7Ge0.3 measured at 800oC: successively higher than the antimony diffusivity in silicon. These results are consistent with later studies.
The results of a diffusivity vs. time study and a diffusivity vs. silicon-germanium composition study are included. Equilibrium antimony diffusion coefficients in alloys of up to 30% germanium are presented along with a possible transient effect. Changes in antimony diffusivity are attributed to changes in the vacancy population and the vacancy enthalpy of migration.
Comparisons with the diffusivity of boron vs. germanium content in silicon-germanium alloys lead to the proposal that, in silicon rich alloys, boron diffuses predominantly via the interstitialcy mechanism. The dependence of diffusivity on germanium content for boron is different to that of antimony and it is proposed that the boron diffusion mechanism changes from largely interstitialcy in silicon to vacancy in germanium - the change occurring at round 40% germanium.
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Published date: 1998
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Local EPrints ID: 463284
URI: http://eprints.soton.ac.uk/id/eprint/463284
PURE UUID: 877a70a5-21fd-48e3-b7b5-4b8808c45cda
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Date deposited: 04 Jul 2022 20:48
Last modified: 04 Jul 2022 20:48
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Author:
Andrew David Nicholas Paine
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