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Crystal growth in materials science

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Crystal growth related twins and point defects in semiconductors and dielectrics

This symposium is aiming to gather people interested in the origin and possible control of grown-in defects in semiconductor and dielectric materials in single or multi-crystalline form. It will mainly focus on "0D" point defects and "2D" twin boundaries. However, point defect interaction with dislocations (1D), dislocation loops (2D), precipitates (3D) may also be considered.

 

Scope:

Bulk single crystals are used in electronic, optoelectronic, optic, sensors, etc. for the unique physical properties they gain from the perfect ordering of their atoms. Consequently, any defect in the structure is potentially detrimental to their use. On the other hand defects, especially point defects such as dopants or color centers, are intentionally added in order to tailor the crystal to its applications.

Twinning is a major defect that totally impairs the use of material for electronic or optical application. In spite of the fact that twins are not impacting photovoltaic efficiency, it has been shown that successive crossing of twins ultimately gives a random grain boundary structure, which is detrimental. In spite of its tremendous drawbacks, the origin of twinning during growth from the melt remains essentially a mystery. Some explanations have been proposed in the past and recent years, but they suffer from a lack of generality, poor quantitative agreement with experimental data and lack of accurate physical properties such as twin boundary energies.

Point defect origin is most well understood in the case of vacancies and interstitials in electronic Si. In spite of significant progress the situation is less clear in the case of compound III-V and II-VI semiconductors. On the other hand little is understood in the case of transparent oxides such as conducting β-Ga2O3 and In2O3 or semiconducting ZnO. Color center and impurity behavior in dielectric crystals is complicated by the iono-covalent bonding in these materials leading to various oxidation states of the dopants as function of the local conditions during growth. In oxides, the effect of growth conditions on point defect distribution and valence states is nearly unknown at the moment.

 

Hot topics to be covered by the symposium:

The symposium is aiming to advance towards answers for the following questions:

  • What is/are the mechanism of twinning during bulk crystal growth?
  • What is the effect of growth parameters on twinning occurrence?
  • How to improve the accuracy of parameters involved in twinning (surface and stacking fault energies)?
  • Is it possible to derive a full set of thermodynamic and kinetic equations describing the behavior of native and extrinsic point defects in compound semiconductors and dielectric crystals?
  • What controls the valence state of color centers in dielectric crystals?
  • What is the relationship between point defect clusters and their aggregations in different materials?
  • To what extent can we attribute the well investigated problem of (non)stoichiometry of compound semiconductors, and its related effects, to oxide and fluoride crystals?
  • How do those native point defects interplay together and with other defects, especially dislocations?

 

Invited speakers:

The invited speakers will also participate to the roundtables organized during the symposium:

 

ROUNDTABLE ON TWINNING:

  • K. Fujiwara (Japan)
  • P. Lagerlorf(USA)
  • N. Mangelinck (France)

 

ROUNDTABLE ON POINT DEFECTS:

  • S. Eichler (Germany) (t. b. confirmed)
  • D.T.J. Hurle (GB) (t. b. confirmed)
  • P. Rudolph (Germany)
  • S. Uda (Japan)
  • C. Van de Walle (USA)

 

Publication:

Proceedings to appear in "Crystal Research and Technology" (Wiley).

 

Sponsors:

 

  logo_hoch_grn  logo_inpact 
 
 freiberger
 
ikz

 

Symposium organizers:

 

Thierry Duffar
Université de Grenoble
SIMAP-EPM
BP 75
F-38402 Saint Martin d'Hères
France
Phone: + 33 (0)4 76 82 52 13
Fax: +33 (0)4 76 82 52 49
thierry.duffar@grenoble-inp.fr

 

Michael Neubert
Leibniz Institut für Kristallzüchtung
Max-Born-Str. 2
D-12489 Berlin
Germany
Phone: +49 30 6392 3030
Fax: +49 30 6392 3003
michael.neubert@ikz-berlin.de

 

Detlef Klimm
Leibniz Institut für Kristallzüchtung
Max-Born-Str. 2
D-12489 Berlin
Germany
Phone: +49 30 6392 3018
Fax: +49 30 6392 3003
detlef.klimm@ikz-berlin.de

 

Michael Dudley
Dept. of Materials Science & Engineering
Stony Brook University
Stony Brook NY 11794-2275
USA
Phone: +1 631 632 8500
Fax: +1 631 632 8052
michael.dudley@stonybrook.edu

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11:15
Authors : IgorAvetissov
Affiliations : D.Mendeleyev University of Chemical Technology of Russia

Resume : The problem of nonstoichiometry (NS) determination in chemical compounds is very important both for crystal growth, film preparation and powdered material production. At the nowadays achieved purity of compound >5N over-stoichiometric components influence on material structure sensitive properties (luminescence, electroconductivity, microhardness, etc.) in the same manner as dopants. Homogeneity ranges of AIVBVI and AIIBVI compounds are commonly estimated as 10-2 mol. %. A precise mass gross analysis does not allow efficiently detecting of NS due to uncertainty in pure element molar mass. Provided non-isotope purity of elements one could take for sure 5 significant figures for composited element molar mass. It means the limit in NS determination of 210-3 mole %. Considering the real accuracy of direct synthesis of binary compound from elements a standard stoichiometric sample could be prepared with ~510-3 mol. % accuracy. It is not enough for some AIIBVI materials in which the impurity level 7N is insufficient for getting of successive characteristics. A universal approach for a development of a NS measurement technique for binary compounds has been proposed. The approach is based on a pi-T-x diagram analysis for binary chemical compounds. The techniques were developed for NS determination in. NS detection limits for PbTe, PbSe, CdS, CdSe, CdTe, ZnSe, ZnTe, HgTe depend on the chemical compound and vary from 10-4 up to 510-6 mol.% with a relative accuracy <18 rel. %.

U.U.II.3
 
POINT DEFECTS 3 : Prof. S. Uda
14:00
Authors : Chris G. Van de Walle
Affiliations : Materials Department, University of California, Santa Barbara, California, USA

Resume : Nitride semiconductors are the key materials for solid-state lighting, and they are also increasingly used for power electronics. For all these applications, high-quality material is essential. In the epitaxial layers that provide device functionality, point defects may act as compensating centers, charge traps, or recombination centers. However, unintentional impurities often play an equally important role; for instance, carbon that is unavoidably incorporated during metal-organic chemical vapor deposition can act as a source of yellow luminescence. Still, point defects are likely to affect the radiative efficiency, and we are actively pursuing the microscopic origins of nonradiative recombination. In parallel, the study of point defects is important in the context of bulk crystal growth, and bulk GaN and AlN are increasingly pursued to be used as substrates for nitride devices. In addition to point defects in GaN, we are focusing on identifying the prevailing defects in AlN, which lead to characteristic luminescence and absorption lines. I will briefly discuss the theoretical advances that are enabling us to calculate the energetics as well as electronic and optical properties of point defects with unprecedented accuracy. Overall, I will focus on examples where defects limit crystal quality or device performance. Work performed in collaboration with A. Janotti, J. Lyons, L. Gordon, and Q. Yan, and supported by DOE and NSF.

U.U.III.1
16:00
Authors : All Symposium chairs
Affiliations : Various

Resume : This will be the roundtable on Point defects

U.U.IV.1
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09:00
Authors : V.K Lazarov, K. McKeena, P.J. Hasnip , D. Gikls, G. Moeen Uddin and M. Weinert*
Affiliations : University of York, UK *University of Wisconsin-Milwaukee, USA

Resume : In this work we study the formation of twins across the interfaces in polar oxide-oxide and polar oxide-semiconductor interfaces, on a case of GaN(111)/MgO(111), MgO(111)/SiC(0001) amd Fe3O4/MgO(111), by experimental including growth (MBE and PLD), atomic level structure characterisation (TEM/STEM), and DFT modelling. Along the polar direction studied system contain of one atomic species per plane, which gives rise of an electrostatic dipole moment along the growth direction. Across the interface in polar heterojunctions, the abrupt change of electrostatic potential leads to atomic interface stacking driven by minimisation of the interface dipole moment. By atomic control of the stacking in the case of GaN/MgO we show that if interface is N-O terminated, a twin related growth of GaN(111) results in formation of the metastable cubic GaN. On the other hand if the growth proceed with Ga at the interface, the twin structure is lost and hexagonal GaN(0001) film is grown. Similarly when MgO(111) films are grown on SiC(0001), electronic properties of the interface can be tuned by forming twin related Mg-Si terminated interfaces, which appeared to be n-doped, and p doped un-twin O-Si terminated interfaces. Finally on the case of spinel-rock salt type of system (Fe3O4-MgO) we show that atomic interface structures with higher energy can be turned into low energy atomic interface structures if twins are formed at the interface. This work demonstrates that polarity and twining at the polar heterostructures can be correlated and effectively used to engineer electronic and atomic structure at a given polar heterostructures.

U.U.V.2
09:15
Authors : C. Renard1, N. Cherkashin2, T. Molière1,3, A. Jaffre3, G. Hallais1, L. Vincent1, J. Alvarez3, D. Mencaraglia3, D. Bouchier1
Affiliations : 1) IEF, Univ Paris-Sud, CNRS, UMR 8622, 91405, Orsay, France; 2) CEMES, CNRS UPR 8011 and Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse, France; 3) LGEP-Supelec, UMR CNRS 8507, Université Pierre et Marie Curie, Université Paris-Sud, 11 rue Joliot Curie, Plateau de Moulon, 91192, Gif sur Yvette, France

Resume : In this work, we investigate the epitaxial lateral overgrowth of micrometer scale GaAs crystals on a 0.6 nm thick SiO2 layer from nanoscale Si seeds in order to develop GaAs monolithic hetero-epitaxy onto (001)Si. The nucleation from small width openings enables to avoid the emission of misfit dislocations and the formation of antiphase domains. The only defects found by transmission electron microscopy in each island are pairs of twins, and a simple model based on the anisotropy of zinc blende crystal is proposed to explain the mechanism of twinning formation during crystal growth. One can expect that the twin formation proceeds as soon as the growing crystal reaches the Si to SiO2 boundary, what alters locally the crystalline order. So, if we consider the lateral growth of GaAs crystal along the [-110] direction, the As atom at the edge of the SiO2 layer cannot bind with a fourth bottom Ga atom, and thus exhibits a dangling bond. In this case, this As atom may "attract" a neighbour Ga atom situated on the SiO2 layer in order to insure the neutrality along the As [110] column at the edge of the SiO2 layer. The resulting bond distortion provokes the anticlockwise rotation of the GaAs lattice by 109.47° around the [110] direction which leads to this {111} twin plane formation [C. Renard, APL 102 (2013) 191915]. Finally, micro-photoluminescence measurements performed at room temperature show that these twins are not detrimental for the quality of microscale GaAs crystals.

U.U.V.3
12:15
Authors : Y. Ping Wang1, J. Stodolna2, T. Nguyen Thanh1, A. Létoublon1, J. Kuyyalil1, N. Bertru1, A. Le Corre1, A. Ponchet2, C. Magen3, J. Even1, C. Cornet1, O.Durand1
Affiliations : 1: Université Européenne de Bretagne, INSA, FOTON-OHM, UMR 6082, F-35708 Rennes, France 2: CEMES-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP94347 Toulouse cedex 04, France 3: INA-Universidad de Zaragoza, Pedro Cerbuna, 12, 50009 Zaragoza, Spain

Resume : The heterogeneous epitaxy of III-V compounds onto Si substrate has been widely studied for decades in the context of low cost monolithic integration of III-V photonics and PVs on silicon. However, most III-V semiconductors on Si lead to a still very high dislocation density (due to a large lattice mismatch). GaP quasi-lattice matched on Si substrate provides an alternative route for the realization of III-V/Si dislocation-free pseudosubstrates. However, Antiphase boundaries (APB) and microtwins (MT) are still difficult to avoid. In this paper, thorough XRD analyses (lab set-up and synchrotron) of 20-nm and 40 nm-thin GaP layers MBE-grown onto Si substrates are presented and combined with AFM and different TEM techniques in order to quantitatively study these defects originating at the GaP/Si interface. The MT XRD and darkfield TEM analyses allowed the improvement of the growth procedure, with the use of a migration enhanced epitaxy technique combined with a two-step growth procedure, leading to a fractional MT volume down to 0.5% of the total GaP layer volume and a lowering of the APB density. We believe here that APB boundaries are vertically oriented in the first step and kink in the second growth step to favor self-annihilation. GaP growth on an optimized Si buffer allowed STEM-HAADF observations of a sharp GaP/Si with double Si steps. This result is very promising for a APB limitation. Support: ANR projects MENHIRS 2011-PRGE-007-01, SINPHONIC N° 2011 JS03 0.

U.U.VI.6
14:00
Authors : All symposium chairmen
Affiliations : Various

Resume : This will be the roundtable on twins

U.U.VII.1
16:00
Authors : Elena Mozhevitina, Andrew Khomyakov, Igor Avetissov.
Affiliations : D.Mendeleyev University of Chemical Technology of Russia

Resume : AIIBVI semiconducting materials have a number of unique properties which significantly depend on nano-scale defect type and concentration. Native point defects generating as a result of deviation from stoichiometric composition influence on luminescence, conductivity, and other structure sensitive properties similar to dopants. In the research nonstoichiometry of ultrapure polycrystalline AIIBVI compounds were studied under both S(AB)LV and S(AB)V equilibria. The deviation from stoichiometry was determined by the ?extraction? technique[1]. In the case of CdS, CdSe, CdTe, ZnTe we found out a high-temperature polymorphic modification at pressures less than 106 Pa contrary to low-temperature zinc blende based modification. For the first time the crystal lattice parameters for powdered hexagonal wurtzite-based ZnTe was obtained using experimental XRD data. We suggested the polymorphous transition accompanied by peritectic reactions from both Chalc- and Me-rich sides. We observed a significant widening of homogeneity limits in a high-temperature polymorph which indicated strong disordering in crystal structure. The vacancy mechanism of disordering was discussed. 1. I. Avetissov et al. Nonstoichiometry and luminescent properties of ZnSe crystals grown from melt and vapor. J. Cryst. Growth 2014.DOI: 10.1016/j.jcrysgro.2014.01.003

U.U.P.9
16:00
Authors : P. Pochet,1 F. D'Acapito,2 F. Somma,3 P. Aloe,3 R. M. Montereali,4 M. A. Vincenti,4 and S. Polosan,5
Affiliations : 1 Laboratoire de Simulation Atomistique (L_Sim), SP2M, CEA/UJF-Grenoble 1, INAC, Grenoble F-38054, France 2 CNR-IOM-OGG c/o ESRF, GILDA-CRG, BP 220, 6 Rue Jules Horowitz, F-38043 Grenoble, France 3 Department of Physics, University of Roma Tre, V. della Vasca Navale 84, I-00146 Roma, Italy 4 ENEA, Photonics Micro- and Nano-Structures Laboratory, UTAPRAD-MNF, C.R. Frascati, V. E. Fermi 45, I-00044 Frascati (Rome), Italy 5 National Institute of Materials Physics, Bucharest-Magurele 077125, Romania

Resume : The growth of Pb doped LiF crystals is not straightforward and has been reported only very recently in the literature. The present study aims to describe the process of LiF doping with Pb using ab initio methods for structural modeling compared to experimental data from X-ray absorption spectroscopy. The values of formation energy of several complexes involving Pb ions show that the presence of charge-balancing vacancies ease the metal incorporation in the crystal [1]. The metal successively captures the vacancies to form a final stable complex that contains a Pb substitutional atom in a Li site and a Li vacancy. Experimental data from X-ray absorption spectroscopy confirm the presence of Pb in LiF crystals in the latter site revealing both Pb-F bonds and collinear Pb-F-Li atomic configurations. A maximum solubility of Pb in LiF of the order of 3 10^20 cm-3 can be estimated from these calculations [1] F. D'Acapito, P. Pochet, F. Somma, P. Aloe, R. M. Montereali, M. A. Vincenti, and S. Polosan Appl. Phys. Lett. 102 081107 (2013) ; http://dx.doi.org/10.1063/1.4793751

U.U.P.13
16:00
Authors : Ameur Zegadi*, Mustapha Rouha, Fatima Zohra Satour
Affiliations : LCCNS, Département d'Electronique, Faculté de Technologie, Université Ferhat Abbas - Sétif 1, Algeria.

Resume : Solar cells based on the ternary compound CuInSe2 and its related alloys Cu(In,Ga)Se2 are attracting increasing attention with reported conversion efficiency above 20%. The interaction of oxygen in CuInSe2 (CIS) is of practical importance. It has already been established that annealing in air or oxygen of the as-fabricated device based on CIS results in an improvement in its performance. The aim of this paper is to present an analysis of non-radiative defect states in oxygen ion implanted CuInSe2 single crystals using a high resolution near-infrared photoacoustic spectrometer of the gas-microphone type. CIS samples, as-grown n-type, have been implanted with O+ at 40 keV with doses of 1015 and 1016 ions/cm2. PAS spectra have been measured before and after implantation. Oxygen has produced significant changes in PA spectra. A theoretical model based on a two-layer configuration has been developed in order to extract the absorption coefficient spectral dependence of the implanted layer from that of the substrate. The latter has been used to establish ionization energies for several intrinsic and extrinsic defect-related states (shallow and deep) that have been observed in the absorption tail of the spectra.The results obtained here are discussed in the light of previously published data.

U.U.P.18

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