Advertisement

The Role of Defects and Metal States at the Metal-Semiconductor Interface

  • R. Ludeke
Part of the NATO ASI Series book series (NSSB, volume 195)

Abstract

Previously proposed Schottky barrier models that attempt a microscopic description of the observed behavior fall basically into the categories of metal induced gap states (MIGS) models 1-5 and defect models.6-9 These two types of models are mutually exclusive, as the MIGS models generally ignore the influence of defects and the defect models, for their part, ignore the importance of screening by the metal. Historically the MIGS models preceded the others and were an outgrowth of Bardeen’s10 suggestion that a large density of interface states was responsible for the generally weak dependence of Schottky barrier heights on the metal (workfunction). Bardeen’s notion that these states derive from the semiconductor surface states (dangling bonds) was incorporated into the MIGS picture by Mele, et al. 3 and recently by Lefebvre, et al. 11, who considered the interaction of metallic states with the empty, cation-derived dangling bond states. The consequence of this interaction is the formation of broadened resonances which tail into the semiconductor bandgap. The rehybridization of the dangling bonds with the metallic states at the interface was not considered. In general the MIGS models encounter difficulties in the alignment of the metal-semiconductor bandstructures, a task which is model dependent.1,4 This problem was circumvented by aligning the MIGS with the charge neutrality level (CNL) of the semiconductor.5’12 The MIGS models are often more successful at estimating the index of interface behavior S\(\left( {S \equiv d\Phi _b^n/d{x_m}} \right)\) where \(\Phi _b^n\) represents the Schottky barrier height for an n-type semiconductor and Xm the Pauling electronegativity of the metal13) since this quantity is insensitive to the magnitude of \(\Phi {}_b^n\), and strongly dependent only on the inverse of the interface density of states Ds.14 Various approaches to calculate Ds have been reported, ranging from self-consistent pseudopotential methods,2 which gave the best agreement with experiment, scaling approaches based on the mean optical gap,3 which give poorer agreement, to one-dimensional model calculations,4 which agree even less with experimental results.

Keywords

Schottky Barrier Metallic State Defect Level Schottky Barrier Height Interface Behavior 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    V. Heine, Phys. Rev. 138, A1689 (1965).ADSCrossRefGoogle Scholar
  2. 2.
    S.G. Louie, J.R. Chelikowsky and M.L. Cohen, Phys. Rev. B15, 2154 (1977).ADSCrossRefGoogle Scholar
  3. 3.
    E.J. Mele and J.D. Joannopoulos, Phys. Rev. B17, 1528 (1978).ADSCrossRefGoogle Scholar
  4. 4.
    E. Louis, F. Yndurain and F. Flores, Phys. Rev. B13, 4408 (1976).ADSCrossRefGoogle Scholar
  5. 5.
    J. Tersoff, Phys. Rev. Lett. 52, 465 (1984); Phys. Rev. B32, 6968 (1985).Google Scholar
  6. 6.
    W.E. Spicer, P.W. Chye, P.R. Skeath, C.Y. Su and I. Lindau, J. Vac. Sci. Technol. 16, 1422 (1979).ADSCrossRefGoogle Scholar
  7. 7.
    W.E. Spicer, T. Kendelewicz, N. Newman, R. Cao, C. McCants, K. Miyano, I. Lindau and E.R. Weber, to be published.Google Scholar
  8. 8.
    R.E. Allen and J.D. Dow, Phys. Rev. B 25, 1423 (1982); and S.-F. Ren and R.E. Allen, Surf. Sci. 148, L637 (1984).Google Scholar
  9. 9.
    W. Walukiewicz, J. Vac. Sci. Technol. B 5, 1062 (1987).CrossRefGoogle Scholar
  10. 10.
    J. Bardeen, Phys. Rev. 71, 717 (1947).ADSCrossRefGoogle Scholar
  11. 11.
    I. Lefebvre, M. Lannoo, C. Priester, G. Allan and C. Delerue, Phys. Rev. B36, 1336 (1987).ADSCrossRefGoogle Scholar
  12. 12.
    C. Tejedor, F. Flores and E. Louis, J. Phys. CIO, 851 (1977).Google Scholar
  13. 13.
    S. Kurtin, T.C. McGill and C.A. Mead, Phys. Rev. Lett. 22, 1433 (1969).ADSCrossRefGoogle Scholar
  14. 14.
    A.M. Cowley and S.M. Sze, J. Appl. Phys. 36, 3212 (1966). Their expression is generally used by most practitioners to calculate S, with differences among the approaches arising from the source and relative magnitudes of Ds.Google Scholar
  15. 15.
    A. Zur, T.C. McGill and D.L. Smith, Phys. Rev. B28, 2060 (1983).ADSCrossRefGoogle Scholar
  16. 16.
    C.B. Duke and C. Mailhiot, J. Vac. Sci. Technol. B3, 1170 (1985).CrossRefGoogle Scholar
  17. 17.
    R. Ludeke, G. Jezequel and A. Taleb-Ibrahimi, Phys. Rev. Lett. 61, 601 (1988); and J. Vac. Sci. Technol. B6, 1277 (1988).Google Scholar
  18. 18.
    K. Stiles and A. Kahn, Phys. Rev. Lett. 60, 440 (1988)ADSCrossRefGoogle Scholar
  19. 19.
    M. Prietsch, M. Domke, C. Laubschat and G. Kaindl, Phys. Rev. Lett. 60, 436 (1988).ADSCrossRefGoogle Scholar
  20. 20.
    G. Jezequel, A. Taleb-Ibrahimi, R. Ludeke and F. Schaffler, J. Vac. Sci. Technol. A6, 1561 (1988).ADSCrossRefGoogle Scholar
  21. 21.
    P.E. Gregory, W.E. Spicer, S. Ciraci and W.A. Harrison, Appl. Phys. Lett. 25, 511 (1974).ADSCrossRefGoogle Scholar
  22. 22.
    R. Ludeke, T.-C. Chiang and T. Miller, J. Vac. Sci. Technol. Bl, 581 (1983).Google Scholar
  23. 23.
    R. Ludeke and G. Landgren,Phys. Rev. B 33, 5526 (1986); G. Hughes, R. Ludeke, F. Schaffler and D. Rieger, J. Vac. Sci. Technol. B4, 924 (1986); F. Schaffler, G. Hughes,W. Drube, R. Ludeke and F.J. Himpsel, Phys. Rev. B35, 6328 (1987). G. Landgren, R. Ludeke, Y. Jugnet, J.F. Morar and F.J. Himpsel, J. Vac. Sci. Technol. B2, 351 (1984); F. Schaffler, W. Drube G. Hughes, R. Ludeke, D. Rieger and F.J. Himpsel, J. Vac. Sci. Technol. A 5, 1528 (1987). 24. J.Y.-F. Tang and J. Freeouf, J. Vac. Sci. Technol. B2, 459 (1984).Google Scholar
  24. 25.
    R. Cao, K. Miyano, T. Kendelewicz, K.K. Chin, I. Lindau and W.E. Spicer, J. Vac. Sci. Technol. B5, 998 (1987).CrossRefGoogle Scholar
  25. 26.
    Clustering is particularly pervasive for metals than interact weakly with the substrate, such as the group III and the noble metals, see for example ref. 22.Google Scholar
  26. 27.
    W. Monch, J. Vac. Sci. Technol. B6, 1270 (1988).CrossRefGoogle Scholar
  27. 28.
    W. A. Harrison, Electronic Structure and the Properties of Solids, W.H Freeman and Co. (San Francisco, 1980).Google Scholar
  28. 29.
    R. Ludeke, unpublished results.Google Scholar
  29. 30.
    J. Ihm and J.D. Joannopoulos, Phys. Rev. B26, 4429 (1982).ADSCrossRefGoogle Scholar
  30. 31.
    L. Brillson, in Handbook of Synchrotron Radiation, Vol. II, Ed. G.V. Marr (North- Holland, Amsterdam, 1985).Google Scholar
  31. 32.
    R.E. Allen and J.D. Dow, J. Vac. Sci. Technol. 19, 383 (1981).ADSCrossRefGoogle Scholar
  32. 33.
    M. Grioni, J.J. Joyce and J.H. Weaver, J. Vac Sci. Technol. A4, 965 (1986); J.J. Joyce, M. Grioni, M. del Giudice, M.W. Ruckman, F. Boscherini and J.H. Weaver, J. Vac. Sci. Technol. A5, 2019 (1987); C.M. Aldao, I.M. Vitomirov, F. Xu and J.H. Weaver, Phys. Rev. B37, 6019 (1988).Google Scholar
  33. 34.
    A. Zunger, Solid State Physics, Vol. 39, Ed. H. Ehrenreich and D. Turnbull (Academic Press, Orlando FL, 1986) p. 275.Google Scholar
  34. 35.
    S. Sze, Physics of Semiconductor Devices, 2nd. Edition (John Wiley & Sons, New York, 1981).Google Scholar
  35. 36.
    M. Jaros, Deep Levels in Semiconductors, (Adam Hilger Ltd., Bristol 1982)Google Scholar
  36. 37.
    G. Landgren, R. Ludeke, Y. Jugnet, J.F. Morar and F.J. Himpsel, J. Vac. Sci. Technol. B2, 351 (1984).CrossRefGoogle Scholar
  37. 38.
    J. Tersoff and W.A. Harrison, J. Vac. Sci. Technol. B5, 1221 (1987).Google Scholar
  38. 39.
    C. Delerue, M. Lannoo and J. M. Langer, Phys. Rev. Lett. 61, 199 (1988).ADSCrossRefGoogle Scholar
  39. 40.
    J.M. Langer and H. Heinrich, Phys. Rev. Lett. 55, 1414 (1985).ADSCrossRefGoogle Scholar
  40. 41.
    A.J. Bennett and L.M. Falicov, Phys. Rev. 151, 512 (1966).ADSCrossRefGoogle Scholar
  41. 42.
    J.W. Gadzuk, Surf. Sci. 6, 133 (1967).ADSCrossRefGoogle Scholar
  42. 43.
    S.K. Lyo and R. Gomer, Topics in Applied Physics Vol 4, ed R. Gomer (Springer, N.Y., 1975) Ch 2.Google Scholar
  43. 44.
    P.K.W. Vinsome and D. Richardson, J. Phys. C, 4, 2650 (1971).ADSCrossRefGoogle Scholar
  44. 45.
    J.C. Inkson, J. Phys. C, 4, 591 (1971).ADSCrossRefGoogle Scholar
  45. 46.
    D.M. Newns, J. Chem. Phys. 50, 4572 (1969).ADSCrossRefGoogle Scholar
  46. 47.
    M.C. Ball and A.H. Norbury, Physical Data for Inorganic Chemists, (Longman Group Ltd., London, 1974).Google Scholar
  47. 48.
    J.C. Phillips, Bonds and Bands in Semiconductors, (Academic Press, New York, 1973).Google Scholar
  48. 49.
    The calculated values of EF are weakly dependent for NA> 1014cm-2, see ref. 17.Google Scholar
  49. 50.
    A. Huijser, J. Van Laar and T.L. Van Rooy, Surf. Sci. 62, 472 (1977).ADSCrossRefGoogle Scholar
  50. 51.
    W.E. Spicer, P.E. Gregory, P.W. Chye, I.A. Babalola and T. Sukegawa, Appl. Phys. Lett.27, 617 (1975); K.K. Chin, S.H. Pan, D. Mo, P. Mahowald, N. Newman, I. Lindau and W.E. Spicer, Phys. Rev B32, 918 (1985).Google Scholar
  51. 52.
    A.B. McLean, D.A. Evans and R.H. Williams, Semicond. Sci. Technol. 2, 547 (1987).ADSCrossRefGoogle Scholar
  52. 53.
    A.B. McLean and R.H. Williams, J. Phys. C 21, 783 (1988).MathSciNetADSGoogle Scholar
  53. 54.
    N. Newman, M. van Schlifgaarde, T. Kendelewicz, M.D. Williams and W.E. Spicer, Phys. Rev B 33, 1146 (1986).MathSciNetADSCrossRefGoogle Scholar
  54. 55.
    W.J. Kaiser and L.D. Bell, Phys. Rev. Lett. 60, 1406 (1988).ADSCrossRefGoogle Scholar
  55. 56.
    V. Mercier, C.A. Sebenne, P. Chen, D. Bolmont and F. Proix, J. Physique 46, 839 (1985).CrossRefGoogle Scholar
  56. 57.
    Z. Liliental-Weber, N. Newman, W.E. Spicer, R. Gronsky, J. Washburn and E.R. Weber, Mat. Res. Soc. Symp. Proc. 54, 415 (1986).CrossRefGoogle Scholar
  57. 58.
    J. Holzl and F.K. Schulte, Workfunction of Metals, in Springer Tracts of Modern Physics, Vol. 85, Springer Verlag, Berlin (1979).Google Scholar
  58. 59.
    M. Schliiter, Phys. Rev. B 17, 5044 (1978).ADSCrossRefGoogle Scholar
  59. 60.
    W. Gordy and W.J. Thomas, Phys. Rev. 24, 439 (1956).Google Scholar
  60. 61.
    J. Tersoff, Phys. Rev. Lett. 56, 2755 (1986).ADSCrossRefGoogle Scholar
  61. 62.
    R.K. Swank, Phys. Rev. 153, 844 (1967); T.E. Fischer, Phys. Rev. 142, 519 (1966); G.W. Gobeli and F.G. Allen, Phys. 137, 245 (1965).Google Scholar
  62. 63.
    J.M. Langer and H. Heinrich, Phys. Rev. Lett. 55, 1414 (1985); J. Tersoff, Phys. Rev. Lett. 56, 675 (1986).Google Scholar
  63. 64.
    Values quoted by Schluter (ref.59), with updated results for GaAs, CdSe, ZnO, ZnS, Si and Ge, from Landolt-Bornstein, New Series v. 17, K.H. Hellwege and O. Madelung, edtrs. (Springer Verlag, Berlin 1984).Google Scholar
  64. 65.
    R. Ludeke and V. Crespi, unpublished results.Google Scholar

Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • R. Ludeke
    • 1
  1. 1.IBM T.J. Watson Research CenterYorktown HeightsUSA

Personalised recommendations