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Title: Electrical Activity of Intragrain Defects in Polycrystalline Silicon Layers Obtained by Aluminum-Induced Crystallization and Epitaxy

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
907990
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 9, 2007; Related Information: Article No. 092103
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; CRYSTALLIZATION; DEFECTS; EPITAXY; SILICON; Solar Energy - Photovoltaics

Citation Formats

Van Gestel, D., Romero, M. J., Gordon, I., Carnel, L., D'Haen, J., Beaucarne, G., Al-Jassim, M., and Poortmans, J.. Electrical Activity of Intragrain Defects in Polycrystalline Silicon Layers Obtained by Aluminum-Induced Crystallization and Epitaxy. United States: N. p., 2007. Web. doi:10.1063/1.2709643.
Van Gestel, D., Romero, M. J., Gordon, I., Carnel, L., D'Haen, J., Beaucarne, G., Al-Jassim, M., & Poortmans, J.. Electrical Activity of Intragrain Defects in Polycrystalline Silicon Layers Obtained by Aluminum-Induced Crystallization and Epitaxy. United States. doi:10.1063/1.2709643.
Van Gestel, D., Romero, M. J., Gordon, I., Carnel, L., D'Haen, J., Beaucarne, G., Al-Jassim, M., and Poortmans, J.. Mon . "Electrical Activity of Intragrain Defects in Polycrystalline Silicon Layers Obtained by Aluminum-Induced Crystallization and Epitaxy". United States. doi:10.1063/1.2709643.
@article{osti_907990,
title = {Electrical Activity of Intragrain Defects in Polycrystalline Silicon Layers Obtained by Aluminum-Induced Crystallization and Epitaxy},
author = {Van Gestel, D. and Romero, M. J. and Gordon, I. and Carnel, L. and D'Haen, J. and Beaucarne, G. and Al-Jassim, M. and Poortmans, J.},
abstractNote = {No abstract prepared.},
doi = {10.1063/1.2709643},
journal = {Applied Physics Letters},
number = 9, 2007,
volume = 90,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The origin of intragrain defects in polycrystalline silicon films grown by ion-assisted deposition (IAD) on aluminum-induced crystallization seed layers on glass is investigated. The microstructure of these polycrystalline Si films is bimodal, with near defect-free regions of (001) orientation along the growth direction and highly defective regions containing smaller grains of (111) orientation. In the defective regions, the dominant structural defects are twins in the seed layer and stacking faults in the IAD-grown epitaxial layer, both lying on (111) planes. The stacking faults originate at the seed layer surface due to surface imperfections, indicating that the quality of the seedmore » layer surface plays an important role for the quality of the epitaxial Si film. We find a clear correlation between the structural crystal quality and defect-related radiative transitions at sub-bandgap wavelengths. Two dominant defect levels ({approx} 0.20 eV and {approx} 0.29 eV below the conduction band edge) are observed and identified as impurity-related.« less
  • We propose a low-temperature laser annealing method of a underwater laser annealing (WLA) for polycrystalline silicon (poly-Si) films. We performed crystallization to poly-Si films by laser irradiation in flowing deionized-water where KrF excimer laser was used for annealing. We demonstrated that the maximum value of maximum grain size of WLA samples was 1.5 {mu}m, and that of the average grain size was 2.8 times larger than that of conventional laser annealing in air (LA) samples. Moreover, WLA forms poly-Si films which show lower conductivity and larger carrier life time attributed to fewer electrical defects as compared to LA poly-Si films.
  • This work focuses on the development and characterization of device quality thin-film crystalline silicon layers directly onto low-temperature glass. The material requirements and crystallographic quality necessary for high-performance device fabrication are studied and discussed. The processing technique investigated is aluminum-induced crystallization (AIC) of sputtered amorphous silicon on Al-coated glass substrates. Electron and ion beam microscopy are employed to study the crystallization process and the structure of the continuous polycrystalline silicon layer. The formation of this layer is accompanied by the juxtaposed layers of Al and Si films exchanging places during annealing. The grain sized of the poly-Si material are manymore » times larger than the film's thickness. Raman and thin-film X-ray diffraction measurements verify the good crystalline quality of the Si layers. The electrical properties are investigated by temperature dependent Hall effect measurements. They show that the electrical transport is governed by the properties within the crystallites rather than the grain boundaries. The specific advantages of AIC are: (1) its simplicity and industrial relevance, particularly for the processes of sputter deposition and thermal evaporation, (2) it requires only low-temperature processing at 500 C, (3) its short processing times, and (4) its ability to produce polycrystalline material with good crystallographic and electrical properties. These advantages make the poly-Si material formed by AIC highly interesting and suitable for subsequent device fabrication such as for poly-Si thin-film solar cells.« less
  • Heavily Si-doped, strain-relaxed In{sub 0.5}Ga{sub 0.5}As layers are often used as contact layers on N{sup +}GaAs to form nonalloyed ohmic contacts. The present work studies the electrical properties of such In{sub 0.5}Ga{sup 0.5}As layers grown on undoped GaAs buffer layers by molecular beam epitaxy both as-grown and after anneals at temperatures between 300 and 430 {degrees}C. It is found that in the as-grown condition, there is a region of about 150 {Angstrom} extending into the In{sub 0.5}Ga{sub 0.5}As layer contiguous to the In{sub 0.5}Ga{sub 0.5}As/GaAs interface where both the electron concentration and mobility decrease toward the interface. With postgrowth anneal,more » the electron concentration in this region will be further reduced and the width of the region will be increased. The associated activation energy is estimated to be 0.99{plus_minus}0.41 eV. This phenomenon can be fully explained in terms of defect structural changes during anneal. This work provides strong evidence to indicate that the as-grown In{sub 0.5}Ga{sub 0.5}As layers are not in thermodynamic equilibrium and will continue to relax when thermal energy is provided. 15 refs., 7 figs.« less
  • Structures of intragrain defects were investigated by photoluminescence (PL) mapping tomography in multicrystalline silicon wafers for solar cells. PL dark patterns were observed in short minority carrier diffusion length regions, and we confirmed that the patterns came from the intragrain defects. The tomography revealed that the defects have planelike structures extended to the crystal growth direction. We also found that the growth conditions affect the structures of the defects: slower solidification leads to larger defects with lower density. Origins of the defects were analyzed by low-temperature PL spectroscopy, electron backscatter diffraction pattern measurement and etch-pit observation. We concluded that themore » defects are metal contaminated dislocation clusters which originate from small-angle grain boundaries.« less