Point defects in silicon after zinc diffusion - a deep level transient spectroscopy and spreading-resistance profiling study

Masuhr, Andreas; Bracht, H.; Stolwijk, N. A.; Overhof, H.; Mehrer, H.

doi:10.1088/0268-1242/14/5/011

Cited by 14 publications

(9 citation statements)

References 14 publications

(32 reference statements)

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“…Although studied to a lesser extent than copper, the other elements of CZTS could also be harmful contaminants for a bottom Si cell. Zinc can introduce near-midgap defect levels in Si as shown in pure diffusion studies [46,47,48]. Tin was studied in particular as a dopant to improve the radiation resistance of c-Si devices, but was also found to form midgap states in Si [49,50].…”

Section: The Need For a Diffusion Barrier Layermentioning

confidence: 99%

Monolithic thin-film chalcogenide–silicon tandem solar cells enabled by a diffusion barrier

Hajijafarassar

Martinho

Stulen

et al. 2020

Solar Energy Materials and Solar Cells

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Following the recent success of monolithically integrated Perovskite/Si tandem solar cells, great interest has been raised in searching for alternative wide bandgap top-cell materials with prospects of a fully earthabundant, stable and efficient tandem solar cell. Thin film chalcogenides (TFCs) such as the Cu 2 ZnSnS 4 (CZTS) could be suitable top-cell materials. However, TFCs have the disadvantage that generally at least one high temperature step (> 500 • C) is needed during the synthesis, which could contaminate the Si bottom cell. Here, we systematically investigate the monolithic integration of CZTS on a Si bottom solar cell. A thermally resilient double-sided Tunnel Oxide Passivated Contact (TOPCon) structure is used as bottom cell. A thin (< 25 nm) TiN layer between the top and bottom cells, doubles as diffusion barrier and recombination layer. We show that TiN successfully mitigates in-diffusion of CZTS elements into the c-Si bulk during the high temperature sulfurization process, and find no evidence of electrically active deep Si bulk defects in samples protected by just 10 nm TiN. Post-process minority carrier lifetime in Si exceeded 1.5 ms, i.e., a promising implied open-circuit voltage (i-V oc) of 715 mV after the high temperature sulfurization. Based on these results, we demonstrate a first proof-of-concept two-terminal CZTS/Si tandem device with an efficiency of 1.1% and a V oc of 900 mV. A general implication of this study is that the growth of complex semiconductors on Si using high temperature steps is technically feasible, and can potentially lead to efficient monolithically integrated two-terminal tandem solar cells.

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Section: The Need For a Diffusion Barrier Layermentioning

confidence: 99%

Monolithic thin-film chalcogenide–silicon tandem solar cells enabled by a diffusion barrier

Hajijafarassar

Martinho

Stulen

et al. 2020

Solar Energy Materials and Solar Cells

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“…4,24 ͑iii͒ All capture transients recorded to determine the capture cross section p exhibit an exponential behavior. This points to isolated point defects rather than to extended defects.…”

Section: A Identification Of the Levelsmentioning

confidence: 99%

Substitutional Zn in SiGe: Deep-level transient spectroscopy and electron density calculations

et al. 2003

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We investigated by deep-level transient spectroscopy a series of p-Si 1ϪX Ge X samples after in-diffusion of Zn. The measurements reveal two deep hole traps which are attributed to the Zn 0/Ϫ single-and Zn Ϫ/2Ϫ double-acceptor states of isolated Zn atoms on substitutional sites. The corresponding transient peaks are broadened for XϾ0 in comparison to those in pure silicon due to statistical fluctuations of the SiGe alloy composition in the local environment of the Zn atoms. This effect is described quantitatively within the alloy-broadening model which furthermore allows to determine the number of atoms sampled by the defect wave function. The results are compared with ab initio calculations for substitutional Zn in pure Si using the linear muffin-tin orbital method in the atomic-spheres approximation based on the local-density approximation. To model the Ge alloying, we have also studied trigonal pairs of substitutional Zn in Si with a single Ge ligand at different pair distances. From these results, the broadening of the transients can be understood qualitatively.

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“…The latter treatment did not contribute to diffusion but served to reduce the concentration of fast diffusing transition metals which may have been unintentionally introduced from the furnace ambient. 40 After diffusion, from each ampoule the P-doped sample͑s͒ were investigated by DLTS to determine the concentration ratio of isolated atoms to pairs C 1 /C 2 . 19 Figure 10 displays the DLTS spectra for selected cases that are relevant to the VT-SRP measurements presented below.…”

Section: B Sample Preparation and Characterizationmentioning

confidence: 99%

Spreading-resistance profiling of silicon and germanium at variable temperature

Voß

Stolwijk

Bracht

2002

Journal of Applied Physics

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The effect of impurity-induced lattice strain and Fermi level position on low temperature oxygen diffusion in silicon J. Appl. Phys. 109, 063532 (2011); 10.1063/1.3555625The effect of preamorphization energy on ultrashallow junction formation following ultrahigh-temperature annealing of ion-implanted silicon J. Appl. Phys. 97, 044501 (2005); 10.1063/1.1844619Profile broadening of high dose germanium implants into (100) silicon at elevated temperatures due to channelingWe have developed the concept of variable-temperature spreading-resistance profiling ͑VT-SRP͒ for the characterization of electrical active impurities or defects in semiconductor crystals. Unlike conventional SRP systems, which are exclusively operated at room temperature, our home-built VT-SRP device allows for measurements at different temperatures typically ranging from 150 to 400 K. VT-SRP is able to combine the accurate resolution of an impurity depth profile with a determination of the predominant impurity-related electronic level in the semiconductor band gap. This feature was exploited on germanium crystals with diffusion-induced gold distributions. Another application concerns the depth profile analysis of foreign elements that occur in various defect configurations. This was demonstrated on Si samples diffused with sulfur or selenium since these impurities may be present as isolated atoms as well as pairs. Given the well-known energy levels of the two S or Se configurations in Si we were able to resolve not only the shape and depth of the diffusion profile but also the ratio of isolated atoms to pairs in the diffusion zone.

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Point defects in silicon after zinc diffusion - a deep level transient spectroscopy and spreading-resistance profiling study

Cited by 14 publications

References 14 publications

Monolithic thin-film chalcogenide–silicon tandem solar cells enabled by a diffusion barrier

Monolithic thin-film chalcogenide–silicon tandem solar cells enabled by a diffusion barrier

Substitutional Zn in SiGe: Deep-level transient spectroscopy and electron density calculations

Spreading-resistance profiling of silicon and germanium at variable temperature

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