Photoluminescence of cw laser-annealed silicon shows a dramatic difference in electronic behavior of the reconstructed material depending upon either creation or suppression of dislocations. Beyond a critical exposure time slip appears, and the luminescence of these samples is dominated by dislocation-related defect levels

Baumgart, H.

Queisser, H. J.

Uebbing, R.H.

Wagner, P.

English

Old Dominion University

Old Dominion University ODU Digital Commons Electrical & Computer Engineering Faculty Publications Electrical & Computer Engineering 1980 Luminescence in Slipped and Dislocation-Free Laser-Annealed Silicon R.H. Uebbing P. Wagner H. Baumgart Old Dominion University, hbaumgar@odu.edu H. J. Queisser Follow this and additional works at: https://digitalcommons.odu.edu/ece_fac_pubs  Part of the Electrical and Computer Engineering Commons, and the Materials Chemistry Commons Original Publication Citation Uebbing, R. H., Wagner, P., Baumgart, H., & Queisser, H. J. (1980). Luminescence in slipped and dislocation-free laser-annealed silicon. Applied Physics Letters, 37(12), 1078-1079. doi:10.1063/1.91869 This Article is brought to you for free and open access by the Electrical & Computer Engineering at ODU Digital Commons. It has been accepted for inclusion in Electrical & Computer Engineering Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact digitalcommons@odu.edu. Luminescence in slipped and dislocation-free laser-annealed silicon R. H. Uebbing, P. Wagner, H. Baumgart, and H.J. Queisser Max-Planck-Institutfiir Festkorperforschung, Heisenbergstrasse 1, D-7000 Stuttgart 80, Federal Republic of Germany (Received 1 S August 1980; accepted for publication 6 October 1980) Photoluminescence of cw laser-annealed silicon shows a dramatic difference in electronic behavior of the reconstructed material depending upon either creation or suppression of dislocations. Beyond a critical exposure time slip appears, and the luminescence of these samples is dominated by dislocation-related defect levels. PACS numbers: 79.20.Ds, 78.55.Ds, 81.40.Ef Laser annealing of imperfect semiconductors has at-tracted much attention 1- 5 as a novel method of improving and controlling structural and electronic properties of semi-conductor materials. Ion-implantation-induced damage can be removed, or amorphous material can be restructured by short-pulse or cw illumination with lasers. The detailed physical properties of such treated materials, however, de-pend strongly on the annealing process and have, as far as optimal degree of perfection is concerned, not been com-pletely determined. This letter reports on photoluminescence studies of cw laser-annealed Si and demonstrates the drastic influence of dislocations generated under specific annealing conditions. Exact control of the laser power and the illumination time is shown to be of great importance for the properties of the annealed material. It has previously been shown that epitaxial regrowth of disordered silicon layers formed by ion implantation can lead to the formation of slip dislocations. 6·7 These disloca-tions are likely to affect the electron-hole recombination. The recombination in turn can be probed very sensitively in photoluminescence experiments. 8 Therefore this method of analysis is used here to investigate the different electronic behavior of Si depending on the presence or absence of dislocations. Silicon wafers were used which had been amorphized by implantation of As, P, or Bat lOOor 180keV with doses of 1 X 10 15-3 X 10 16 atoms/cm2 on ( 100) and ( 111) surfaces. The implanted samples were annealed by irradiation with a 15-W cw Ar ion laser in the TEM00 mode. The exposure time was adjusted by means of an electromechanical shutter or by scanning the wafers with a computer-controlled xy table with 5-µm step resolution. The laser intensity was adjusted and controlled by regulation of the excitation current. The degree of lattice perfection was analyzed by x-ray topogra-phy, optical micrography, and preferential etching tech-niques as previously described. 6·7 Figure 1 gives an example of optical micrographs taken from slipped as well as from nonslipped single-shot expo-sures. Comparison of the annealing parameters (see figure caption) reveals that a change in exposure time of only about 15% leads to a transition from nonslipped to slipped silicon. In addition, a change in power density of about 20% (from 7 to 8.5 W) causes a transition from solid phase epitaxial (SPE) to liquid phase epitaxial growth (LPE).9 These annealing procedures thus constitute a highly controlled method of preparing samples with or without dislocations, but other-wise largely identical in structure, chemical composition, and thermal history. Comparatively small variations of the anneal conditions can thus result in different crystalline per-fection with severe consequences for the electronic proper-ties. Figure 2 shows the luminescence spectra of two large-area annealed samples. Anneal conditions are identical to those in Fig. 1. Photoluminescence is excited with S 14-nm (a) (b) t----t 2 c; ,.rn ~ 2S pm FIG. I. Solid phase epitaxial regrowth shown in differential interference contrast: (a) laser exposure at 6 W, 30 ms, no slip dislocations; (b) 7 W, 100 ms, cross grid of slip lines reveals dislocations. 1078 Appl. Phys. Lett. 37(12), 15 December 1980 003-6951 /80/ 241078-02$00.50 (c) 1981 American Institute of Physics 1078 vi o, P implanted + ·2: 4.2 K ~ .Li BE ;; ..... >- bl I-iii z w I- BE ~ w u z w u EHD Vl -w z a) :i :::i ....J 1.6 1.4 12 1.0 WAVELENGTH (µm] FIG. 2. Photoluminescence spectra of P-implanted laser-annealed Si. Large-area annealing with identical regrowth mode is in Fig. 1. la) Without dislocations. (b) With dislocations; intensity enlarged fourfold relative to la). Ar laser light, and recorded with a grating monochromator (Jobin Yvon H 25) and a selected cooled Ge diode detector (North Coast EO-8 l 7L). The dislocation-free sample exhib-its the well-known emission lines of bound-exciton (BE) and electron-hole drops (EHD's). The presence ofEHD lumines-cence indicates relatively long carrier lifetimes. The sample containing dislocations (estimated density about 108 disloca-tions/cm2), on the other hand, shows no EHD emission; in-stead four new intense and broad lines are seen and marked D1-D4 in Fig. 2(b). These lines were formerly found by Drosdov et al. 10• 11 in plastically deformed bent silicon crys-tals and have been attributed to dislocations. The exact ener-getic positions and the relative intensities of these four lines are sample dependent. Usually, our samples show lines D1 and D4 as most intense and also exhibit a fine structure dif-ferent from Ref. 11. Further details, including studies of the influence of temperature, excitation intensity, and disloca-tion density will be published elsewhere. 12 No dependence on the chemical nature of the dopant is found: As, P, and B reveal no significant difference in the D lines, but of course show their respective characteristic bound excitons. We also see no influence of the crystal orientation. Although the atomic structure of the recombination centers is as yet not clarified, our experiments confirm the previous assignment 10•11 of the D lines as being caused by the 1079 Appl. Phys. Lett., Vol. 37, No. 12, 15 December 1980 presence of dislocations. Other authors have also reported photoluminescence oflaser-annealed silcon. 13 Their spectra generally show a multitude ofbroad bands which we cannot detect in our SPE regrown material. Our LPE material, 6 '7 however, also shows rather broad and structureless spectra. We believe that our results are significant in two re-spects. First, anneal conditions have to be properly chosen and controlled in order to achieve the dislocation-free SPE-regrown, rather than the dislocated, lattice. Only under these conditions can one obtain well-defined electronic be-havior resembling that of perfect single-crystal bulk silicon. Secondly, cw laser annealing provides an extremely well controlled means of generating dislocations in silicon for fur-ther detailed studies of this type of defect. The authors are much indebted to G. A. Rozgonyi and J. Weber for helpful discussions. Thanks are due to H. Schenk from AEG-Telefunken, Heilbronn, who provided us with some of the implanted samples, as well as to W. Heinz and H. Klann for their fine technical assistance. 'G. A. Rozgonyi, in Festkorperprobleme (Advances in Solid State Physics), Vol. XX, edited by J. Treusch (Braunschweig, 1980), p. 229. 2 J. F. Gibbons, in Laser and Electron Beam Processing of Electronic Materi-als, edited by C. L. Anderson, G. K. Celler, and G. A. Rozgonyi (Electro-chemical Society, Princeton, N. J., 1979). 31. B. Khaibullin, E. I. Shtyrkov, M. M. Zaripov, R. M. Bayazitov, and M. F. Galjautdinov, Radiat. Elf. 36,225 (1978), and references therein. 4G. Foti, E. Rimini, G. Vitali, and M. Bertolotti, Appl. Phys. 14, 189 (1977). 51. C. Kimmerling and J. L. Benton, in Symposium A, Materials Research Society Meeting, Cambridge, Mass., 1979, edited by C. W. White and P. S. Peercy (Academic, New York, 1980). 6 G. A. Rozgonyi and H. Baumgart, J. Phys. (Paris) 41, Suppl. 5, C4-85 (1980). 7H. Baumgart, F. Philipp, G. A. Rozgonyi, and U. Gosele (unpublished). 8H. J. Queisser, Appl. Phys. 10,275 (1976). 91. S. Williams, W. L. Brown, H.J. Leamy, J. M. Poate, J. W. Rogers, D. Rousseau, G. A. Rozgonyi, J. A. Shelnutt, and T. T. Sheng, Appl. Phys. Lett. 33, 542 (1978). wN. A. Drosdov, A. A. Patrin, and V. D. Tkachev, Zh. Eksp. Theor. Fiz., Pis' ma Red. 23,651 (1976) [Soviet. Phys. J. Exper. Theor. Phys. Lett. 23, 597 (1976)]. ''N. A. Drosdov, A. A. Patrin, and V. D. Tkachev, Phys. Status Solidi (b) 83, K137 (1977). 12R. A. Street, N. M. Johnson, and J. F. Gibbons, J. Appl. Phys. 50, 8201 (1979). Uebbing et al. 1079 

Luminescence in Slipped and Dislocation-Free Laser-Annealed Silicon

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Luminescence in Slipped and Dislocation-Free Laser-Annealed Silicon

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