Injection dependence of the effective lifetime of n-type Si passivated by Al2O3: An edge effect?

Veith, Boris; Ohrdes, Tobias; Werner, Florian; Brendel, Rolf; Altermatt, Pietro P.; Harder, Nils‐Peter; Schmidt, Jan

doi:10.1016/j.solmat.2013.06.049

Cited by 48 publications

(49 citation statements)

References 15 publications

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“…The significant dip in the lifetime of the p-type samples in low injection is likely due to bulk Shockley-Read-Hall recombination, while the apparent lack of an injection dependence in the lifetimes of the n-type samples is probably due to a depletion region modulation effect. Both dependencies are also observed for the same type of substrates passivated with PA-ALD Al 2 O 3 layers [28].…”

Section: Experimental Methodsmentioning

confidence: 56%

“…2 shows the injection dependence of the lifetime at each stage for several representative samples. In principle, the negative charge of Al 2 O 3 could be expected to result in surface recombination velocities that are independent of the excess carrier concentration in low injection for p-type substrates, but strongly injection-dependent for n-type substrates [28]. However other recombination mechanisms and measurement artefacts may also influence the effective lifetime.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Thermal stability of silicon surface passivation by APCVD Al2O3

Black

Allen

Cuevas

et al. 2014

Solar Energy Materials and Solar Cells

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a b s t r a c tWe investigate the thermal stability of silicon surface passivation provided by aluminium oxide (Al 2 O 3 ) films deposited using atmospheric pressure chemical vapour deposition (APCVD) and fired in a belt furnace at a peak temperature of $ 810 1C. Firing stability is investigated for p-and n-type substrates as a function of Al 2 O 3 film thickness both with and without a plasma-enhanced chemical vapour deposition (PECVD) SiN x capping layer, and for boron-diffused surfaces with a $ 10 nm Al 2 O 3 film only. Excellent thermal stability of the passivation is demonstrated, with effective carrier lifetimes in n-type silicon wafers remaining stable or even improving after firing, and lifetimes in p-type wafers initially degrading slightly but recovering to above their initial values following $ 10 min illumination by a halogen lamp at $ 20 mW/cm 2 . Film thickness appears to be unimportant to stability, as does the presence of the capping layer. Surface recombination velocities of less than 3 cm/s for 1.35 Ω cm p-type and less than 2 cm/s for 1.2 Ω cm n-type substrates are measured after firing and illumination. The passivation of boron-diffused surfaces is also shown to improve slightly following firing, with a post-firing saturation current density of 42 fA/cm 2 on a diffusion with a sheet resistance of 100 Ω/□ and surface dopant concentration of $ 1.3 Â 10 19 cm −3 . Capacitance-voltage (C-V) measurements show that short firing times result in an initial reduction of the interface defect density D it and a slight increase of the negative insulator fixed charge density Q f , while longer firing results in a substantial increase in both Q f and D it .

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Section: Experimental Methodsmentioning

confidence: 56%

Section: Experimental Methodsmentioning

confidence: 99%

Thermal stability of silicon surface passivation by APCVD Al2O3

Black

Allen

Cuevas

et al. 2014

Solar Energy Materials and Solar Cells

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“…The level of surface passivation is relatively constant at low injection level for p-type silicon. The decrease in lifetime of n-type silicon at low injection levels is attributed to edge recombination of the samples, as was shown by Veith et al [7], due to the relatively small sample size.…”

Section: Resultsmentioning

confidence: 56%

Effective silicon surface passivation by atomic layer deposited Al₂O₃/TiO₂ stacks

Suh

Weber

2013

Physica Rapid Research Ltrs

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In this work atomic layer deposition of Al2O3 and TiO2 has been used to obtain dielectric stacks for passivation of silicon surfaces. Our experiments on n‐ and p‐type silicon wafers deposited by thin Al2O3/TiO2 stacks show that a considerably improved passivation is obtained compared to the Al2O3 single layer. For Al2O3 films thinner than 20 nm the emitter saturation current density decreases with increasing TiO2 thickness. Especially the passivation of ultrathin (∼5 nm) Al2O3 is very effectively enhanced by TiO2 due to a decreased interface defect density as well as an increased fixed negative charge in the stacks. Hence, the thin Al2O3/TiO2 stacks developed in this work can be used as a passivation coating for Si‐based solar cells. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…The probed area is a circle with diameter of 1 mm and the excitation spot has a diameter of 10 mm to minimize lateral diffusion and edge effects. 15,28 For comparison, spatially-averaged injection level dependence of the effective lifetime is determined by quasi steady state photoconductance (QSSPC) using a Sinton Consulting WCT-120 lifetime tester. 30 The total measured area by QSSPC is about 2 Â 2 cm 2 .…”

Section: Methodsmentioning

confidence: 99%

“…26,27 For simplicity, we assume a single mid-gap defect in the bulk with equal electron and hole time constants (s n0 ¼ s p0 ), per Ref. 28, and s n0 is used as a fit parameter. Apart from bulk recombination, carriers can also recombine at the surface of the sample and the recombination rate is equal to the product of the surface recombination velocity (SRV) and carrier densities.…”

Section: B Recombination Modelsmentioning

confidence: 99%

Proof-of-concept framework to separate recombination processes in thin silicon wafers using transient free-carrier absorption spectroscopy

Siah

Winkler

Powell

et al. 2015

Journal of Applied Physics

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We present a proof-of-concept framework to independently determine the bulk Shockley-Read-Hall (SRH) lifetime and surface recombination velocity in silicon wafers self-consistently. We measure the transient decay of free-carrier absorption (FCA) using two different excitation wavelengths (1050 and 750 nm) for p-type crystalline Si (c-Si) wafers over a wide injection range and fit the FCA transients for the two excitation wavelengths in a coupled manner. In this way, we can estimate the surface recombination lifetime accurately. However, we find that the capability to uniquely measure extrinsic bulk-SRH recombination is challenging in the presence of other recombination processes and can be broadly categorized into five different regimes depending on the relative strengths of each recombination pathway.

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Injection dependence of the effective lifetime of n-type Si passivated by Al2O3: An edge effect?

Cited by 48 publications

References 15 publications

Thermal stability of silicon surface passivation by APCVD Al2O3

Thermal stability of silicon surface passivation by APCVD Al2O3

Effective silicon surface passivation by atomic layer deposited Al₂O₃/TiO₂ stacks

Proof-of-concept framework to separate recombination processes in thin silicon wafers using transient free-carrier absorption spectroscopy

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Injection dependence of the effective lifetime of n-type Si passivated by Al2O3: An edge effect?

Cited by 48 publications

References 15 publications

Thermal stability of silicon surface passivation by APCVD Al2O3

Thermal stability of silicon surface passivation by APCVD Al2O3

Effective silicon surface passivation by atomic layer deposited Al2O3/TiO2 stacks

Proof-of-concept framework to separate recombination processes in thin silicon wafers using transient free-carrier absorption spectroscopy

Contact Info

Product

Resources

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Effective silicon surface passivation by atomic layer deposited Al₂O₃/TiO₂ stacks