Deposition and extensive light soaking of highly pure hydrogenated amorphous silicon

Kamei, Toshihiro; Hata, Nobuhiro; Matsuda, Akihisa; Uchiyama, Toyoshi; Amano, Shigeru; Tsukamoto, Kazuyoshi; Yoshioka, Yoshiaki; Hirao, Takashi

doi:10.1063/1.116140

Cited by 53 publications

(12 citation statements)

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“…Therefore, we believe that we deal with three different types of defects and the question arises which microscopic atomic configurations introduce the D h and D e states. We exclude that impurity atoms such as oxygen or carbon are the origin of the gap states as demonstrated by Kamei et al 31 and consider only atomic configurations including Si and H atoms to be candidates for introducing the D h and D e gap states. We also rule out Si-H bonds as candidates for the D h and D e states since the Si-H bonds do not introduce states into the band gap.…”

Section: Origin Of Charged Gap Statesmentioning

confidence: 99%

Origin of charged gap states ina-Si:H and their evolution during light soaking

Nádaždy

Zeman

2004

Phys. Rev. B

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We report on the evolution of three groups of gap states (D h ,D z , and D e ) in the charge deep-level transient spectroscopy ͑Q-DLTS͒ spectra during light soaking of undoped hydrogenated amorphous silicon (a-Si:H͒. Recently, correlation between Q-DLTS and electron-spin resonance showed that neutral (D z ) states correspond to neutral dangling-bond defects. The present Q-DLTS spectra demonstrate the annihilation of positively charged (D h ) states above midgap different from dangling-bonds in the early stage of light soaking. The initial decrease of the D h states is not accompanied by an increase in the D z or negatively charged (D e ) states below midgap. Further, we do not observe a direct correlation in light induced changes of all three groups of defect states. Combining our results with findings from recent nuclear magnetic resonance experiments at low temperature and computer simulations of a-Si:H network, microscopic configurations introducing charged gap states are proposed. Positively charged states are related to a complex formed by a hydrogen molecule and a Si dangling bond. Negatively charged states are attributed to the floating bonds. A comprehensive model for the Staebler-Wronski effect ͑SWE͒ is presented, which overcomes a weak point of previous models regarding the origin of mobile hydrogen and provides new insight into complexity of the SWE.

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Section: Origin Of Charged Gap Statesmentioning

confidence: 99%

Origin of charged gap states ina-Si:H and their evolution during light soaking

Nádaždy

Zeman

2004

Phys. Rev. B

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“…Conventional a-Si:H films contain other impurities such as oxygen, carbon, and nitrogen with concentrations of 10 18 -10 20 cm Ϫ3 . 39 However, a high-purity undoped film, which contains no more than 10 16 cm Ϫ3 of impurities, still reveals the band-tail structure in its optical absorption spectrum. 39 Therefore, we speculate that the impurities do not directly relate to the formation of weak bonds, and thus the weak bond may be an intrinsic structure of the amorphous silicon network.…”

Section: A Origin Of Lesr Centersmentioning

confidence: 99%

Microscopic origin of light-induced ESR centers in undoped hydrogenated amorphous silicon

Umeda

Yamasaki²,

Isoya

et al. 2000

Phys. Rev. B

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29 Si hyperfine ͑hf͒ structures of light-induced electron-spin-resonance ͑LESR͒ centers of gϭ2.004 and 2.01 have been investigated in undoped hydrogenated amorphous silicon (a-Si:H) with different 29 Si content ͑1.6, 4.7,9.1 at. %͒ by means of pulsed and multifrequency ͑3,11,34 GHz͒ ESR techniques. We have experimentally deconvoluted overlapping LESR signals using the difference in the spin-lattice relaxation time between the two signals. The deconvoluted 29 Si hf structure of gϭ2.004 indicates that the wave function of the gϭ2.004 center spreads mainly over two Si atoms. Accordingly, we propose that the origin of gϭ2.004 is electrons trapped in antibonding states of weak Si-Si bonds rather than those trapped at positively charged dangling bonds. The isotropic hf splittings were estimated to be around 7 mT for gϭ2.004 and below 3 mT for gϭ2.01, which are in good agreement with characteristics of the antibonding and bonding states of the weak Si-Si bond. We suggest, from our 29 Si hf data and other experimental findings, that the gϭ2.004 center is localized spatially more than conduction-band-tail electrons detected by photoluminescence.

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“…Nevertheless, it was not possible to decide whether the doping effect is connected with an activation of the electrically inactive donors or is inherent to a-Si:H network itself. A common feature of the above mentioned experiments is that DLTS technique was applied to doped a-Si:H. Since it was proved 5 that metastability of electrical properties due to changes in the gap states distribution is inherent to the network only consisted of Si and H atoms, the study of gap states in undoped a-Si:H has a key importance.…”

Section: Introductionmentioning

confidence: 99%

Correlation between the results of charge deep-level transient spectroscopy and ESR techniques for undoped hydrogenated amorphous silicon

et al. 2002

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Results of charge deep-level transient spectroscopy ͑DLTS͒ and electron spin resonance ͑ESR͒ measurements on undoped hydrogenated amorphous silicon (a-Si:H͒ clearly demonstrate that a group of gap states with a mean energy of 0.82 eV as observed in charge DLTS experiments for a-Si:H based metal/oxide/ semiconductor structure is the same as the gϭ2.0055 ESR defect ͑the D z component͒. This correlation provides a distinct marker for charge DLTS technique. We obtained a very good fit to spectra obtained on undoped a-Si:H in the annealed state whilst there is some discrepancy between the experimental and simulated spectra for the light-soaked state. The first quantitative comparison of defect pool model with gap states directly observed by charge DLTS offers not only additional data for more accurate identification of all the intrinsic and light-induced defects. This also renders distinct counter-evidence to recently published conjectures about the creation of another charged defect during early stage of Staebler-Wronski effect. By contrast, our presented results clearly argue for opposite process, i.e., decay of positively charged defect states D h .

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Deposition and extensive light soaking of highly pure hydrogenated amorphous silicon

Cited by 53 publications

References 0 publications

Origin of charged gap states ina-Si:H and their evolution during light soaking

Origin of charged gap states ina-Si:H and their evolution during light soaking

Microscopic origin of light-induced ESR centers in undoped hydrogenated amorphous silicon

Correlation between the results of charge deep-level transient spectroscopy and ESR techniques for undoped hydrogenated amorphous silicon

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