Density of states and relaxation spectra of etched, H-terminated and naturally oxidized Si-surfaces and the accompanied defects

Flietner, H.; Füssel, W.; Sinh, Ngo Duong

doi:10.1016/s0169-4332(96)00168-7

Cited by 13 publications

(17 citation statements)

References 23 publications

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“…"43 parameters. This follows early reports on the existence of such states [31,32], and recent work pointing out their importance [33,34]. From Figure 2 it is clear that charge at and near the Si-SiO2 interface can control the surface concentration of carriers, and thus the extent of surface recombination.…”

Section: Charge In the Srh Model Of Surface Recombinationsupporting

confidence: 84%

Charge fluctuations at the Si–SiO2 interface and its effect on surface recombination in solar cells

Bonilla

Al‐Dhahir

et al. 2020

Solar Energy Materials and Solar Cells

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The Si-SiO2 interface has and will continue to play a major role in the development of silicon photovoltaic devices. This work presents a detailed examination of how charge at or near this interface influences device performance. New understanding is identified on the effect of charge-induced potential fluctuations at the silicon surface. Such fluctuations have been considered in Si-SiO2 recombination models previously, where a universal value of electrical potential deviation was used to represent the effect. However, the approach disregards that the variation occurs in the charge concentration rather than the potential. We modify the models to accurately reflect fluctuations in external charge, allowing a precise representation of surface recombination velocity, with self-consistent !" , # , and $ parameters. Correctly accounting for these parameters can provide insights into the passivation mechanisms which can aid the development of future devices. Using the corrected model, we find that the effect of charge fluctuation at the Si-SiO2 interface is significant for the depletion regime to the weak inversion regime. This indicates that surface passivation dielectrics must operate with charge concentrations in excess of 2x10 12 q/cm 2 to avoid these effects. TCAD device simulations show that the efficiency of future PERC cells can improve up to 1% absolute when optimally charged dielectric coatings are applied both at the front and rear surfaces.

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Section: Charge In the Srh Model Of Surface Recombinationsupporting

confidence: 84%

Charge fluctuations at the Si–SiO2 interface and its effect on surface recombination in solar cells

Bonilla

Al‐Dhahir

et al. 2020

Solar Energy Materials and Solar Cells

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“…In agreement with previous suggestions 37 we find that a strong charge rearrangement accompanies the relaxation, with roughly 0.2e per atom transferred from the first Si layer to the second, while the H atoms carry an excess of 0.04e per atom; these values are in good agreement with the estimates from capacitance-voltage measurements. 31 The above results show that the surface rearrangements give ionicity not only to Si-H bonds, but also to the back-bonds, strengthening both and creating the stable surface reported experimentally. 34 As said above, the preparation of this stable surface usually involves etching of the oxidized surface, which is known to yield large, flat (1 × 1) terraces.…”

Section: Test Systems: Si-a Center and Special Moleculessupporting

confidence: 63%

QUANTUM-CHEMISTRY STUDY OF SEMICONDUCTOR SYSTEMS: THE INITIAL OXIDATION OF THE (111)Si-H SURFACE

Baierle

Caldas

1999

Int. J. Mod. Phys. B

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We propose a well-defined procedure to adapt a Quantum-Chemistry technique for the study of semiconductor structures. The procedure comprises use of a Bloch-periodic version of the standard molecular code and a nanocrystal cluster model. We reparametrize according to this procedure the MNDO/AM1 technique for Si and O and present this new parametrization AM1/Crystal. We apply AM1/Crystal to study oxidation of the hydrogenated silicon(111) surface, at the initial stages, when the absorbed oxygen atoms form isolated surface defects. We obtain self-consistent charge distributions and total energies for optimised geometries of different incorporation sites and configurations, including up to three oxygen atoms. We also obtain vibrational frequencies for the complexes that compare well with available experimental data. Our results confirm that backbond incorporation (Si-O-Si-H) is energetically favored compared to a surface hydroxyl configuration (Si-OH) and indicate that the first subsurface layer incorporation should proceed by island formation in a two-dimensional regime.

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“…This continuum is made up of separate contributions from different species of states with different properties. The available evidence suggests that each of these sub-distributions may be approximately described by a Gaussian function centred around a certain energy [9], [134]. The energy levels of the states associated with such defects in principle depend on the local chemical environment of each defect.…”

Section: Interface State Distributionmentioning

confidence: 99%

New Perspectives on Surface Passivation: Understanding the Si-Al2O3 Interface

Black

2016

Springer Theses

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High-efficiency crystalline silicon solar cells must suppress recombination at their p-type surfaces. Thin-film, amorphous aluminium oxide (Al 2 O 3) has been shown to provide very effective passivation of such surfaces, assisted by its negative fixed charge. However, many details of Al 2 O 3 passivation remain poorly understood. Furthermore, conventional means of depositing passivating Al 2 O 3 are too slow or too expensive to be suitable for high-volume commercial production. This thesis addresses these issues in three ways: 1) by contributing to a deeper understanding of semiconductor-dielectric interfaces and semiconductor surface recombination mechanisms in general, 2) by investigating the properties of Al 2 O 3 as a passivating dielectric for silicon surfaces, and 3) by demonstrating the viability of APCVD as a high-throughput, industrially compatible deposition method for Al 2 O 3 , enabling its application to commercial solar cells. Using Al 2 O 3 as a test case, it is shown how a novel analysis of the extended conductance method can be used to i) distinguish the separate contributions to the interface state distribution at a semiconductor-dielectric interface, and ii) determine their capture cross-sections for both minority and majority carriers. Furthermore, the direct link between these measured interface state properties and the recombination rate at the semiconductor surface is experimentally demonstrated by showing that the former can be used to accurately predict the latter. Investigations of the surface passivation properties of Al 2 O 3 reveal a remarkably consistent picture. It is shown that the properties of the Si-Al 2 O 3 interface states are essentially independent of the Al 2 O 3 deposition conditions and technique. The interface properties are found to be independent of the surface dopant concentration at boron-and phosphorus-doped surfaces, while recombination is shown to be only weakly dependent on surface orientation and morphology as a result of the remarkable orientation-independence of the Si-Al 2 O 3 interface state properties. Meanwhile, the chemical origin of the charge at the Si-Al 2 O 3 interface is elucidated by correlating FTIR and electrical measurements. xi xii APCVD is clearly shown-for the first time-to be capable of depositing Al 2 O 3 films with exceptional surface passivation properties, comparable to the best results achieved using other deposition techniques. In the best case, interface state densities as low as 5 × 10 10 eV −1 cm −2 at midgap, and negative fixed charge concentrations of 3.3 × 10 12 cm −2 are measured, resulting in a saturation current density of 7 fA cm −2 on undiffused p-type surfaces. The APCVD films are shown to be thermally stable under standard solar cell processing conditions and are demonstrated in large-area solar cells with peak efficiencies of 21.3 %. These results demonstrate the viability of APCVD Al 2 O 3 as a surface passivation layer for industrial silicon solar cells.

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Density of states and relaxation spectra of etched, H-terminated and naturally oxidized Si-surfaces and the accompanied defects

Cited by 13 publications

References 23 publications

Charge fluctuations at the Si–SiO2 interface and its effect on surface recombination in solar cells

Charge fluctuations at the Si–SiO2 interface and its effect on surface recombination in solar cells

QUANTUM-CHEMISTRY STUDY OF SEMICONDUCTOR SYSTEMS: THE INITIAL OXIDATION OF THE (111)Si-H SURFACE

New Perspectives on Surface Passivation: Understanding the Si-Al2O3 Interface

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