Abstract
Supersaturated levels of interstitial oxygen in Czochralski silicon can lead to the formation of oxide precipitates. Although beneficial from an internal gettering perspective, oxygen-related extended defects give rise to recombination which reduces minority carrier lifetime. The highest efficiency silicon solar cells are made from n-type substrates in which oxide precipitates can have a detrimental impact on cell efficiency. In order to quantify and to understand the mechanism of recombination in such materials, we correlate injection level-dependent minority carrier lifetime data measured with silicon nitride surface passivation with interstitial oxygen loss and precipitate concentration measurements in samples processed under substantially different conditions. We account for surface recombination, doping level, and precipitate morphology to present a generalised parameterisation of lifetime. The lifetime data are analysed in terms of recombination activity which is dependent on precipitate density or on the surface area of different morphologies of precipitates. Correlation of the lifetime data with interstitial oxygen loss data shows that the recombination activity is likely to be dependent on the precipitate surface area. We generalise our findings to estimate the impact of oxide precipitates with a given surface area on lifetime in both n-type and p-type silicon.
Highlights
Czochralski silicon (Cz-Si) usually contains 1017–1018 cmÀ3 of interstitial oxygen, which is incorporated from the walls of the silica crucible which contains the melt
In order to quantify and to understand the mechanism of recombination in such materials, we correlate injection level-dependent minority carrier lifetime data measured with silicon nitride surface passivation with interstitial oxygen loss and precipitate concentration measurements in samples processed under substantially different conditions
We account for surface recombination, doping level, and precipitate morphology to present a generalised parameterisation of lifetime
Summary
Czochralski silicon (Cz-Si) usually contains 1017–1018 cmÀ3 of interstitial oxygen, which is incorporated from the walls of the silica crucible which contains the melt. The oxygen is supersaturated and this provides a driving force for precipitation. Precipitate nuclei can be formed intentionally by careful thermal processing, and in silicon for integrated circuits, oxide precipitates are deliberately formed away from the active region of a device to provide internal gettering centres for harmful metallic impurities.. Oxide precipitates initially form as unstrained particles and, as they grow, they undergo a morphological transformation into strained ones.. As precipitates grow with further processing, dislocations and/or stacking faults can form around the oxide precipitates. The precipitates must be strained in order for them to getter impurities.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
