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New and unified model for Schottky barrier and III-V insulator interface states formation

  • W. E. Spicer
  • P. W. Chye
  • P. R. Skeath
  • C. Y. Su
  • I. Lindau
Part of the Perspectives in Condensed Matter Physics book series (PCMP, volume 4)

Abstract

For n- and p-doped III-V compounds, Fermi-level pinning and accompanying phenomena of the (110) cleavage surface have been studied carefully using photoemission at hv≲ 300 eV (so that core as well as valence band levels could be studied). Both the clean surfaces and the changes produced, as metals or oxygen are added to those surfaces in submonolayer quantities, have been examined. It is found that, in general, the Fermi level stabilizes after a small fraction of a monolayer of either metal or oxygen atoms have been placed on the surface. Most strikingly, Fermi-level pinning produced on a given semiconductor by metals and oxygen are similar. However, there is a strong difference in these pinning positions depending on the semiconductor: The pinning position is near (1) the conduction band maximum (CBM) for InP, (2) midgap for GaAs, and (3) the valence band maximum (VBM) for GaSb. The similarity in the pinning position on a given semiconductor produced by both metals and oxygen suggests that the states responsible for the pinning resulted from interaction between the adatoms and the semiconductor. Support for formation of defect levels in the semiconductor at or near the surface is found in the appearance of semiconductor atoms in the metal and in disorder in the valence band with a few percent of oxygen. Based on the available information on Fermi energy pinning, a model is developed for each semiconductor with two different electronic levels which are produced by removal of anions or cations from their normal positions in the surface region of the semiconductors. The pinning levels have the following locations, with respect to the VBM: GaAs, 0.75 and 0.5 eV; InP, 0.9 and 1.2 eV (all levels + 0.1 eV).

Keywords

Fermi Level Interface State Schottky Barrier Defect Level Valence Band Maximum 
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.

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References

  1. 1.
    J. van Laar and J. J Scheer, Surf. Sci 8, 342 (1967); J. van Laar and A. Huijser, J. Vac. Sci. Technol. 13,769 (1976).Google Scholar
  2. 2.
    W. Gudat and D. E. Eastman, J. Vac. Sci. Technol 13,831 (1976).CrossRefGoogle Scholar
  3. 3.
    W. E. Spicer, I. Lindau, P. E. Gregory, C. M. Garner, P. Pianetta, and P. Chye, J. Vac. Sci. Technol. 13,780 (1976).CrossRefGoogle Scholar
  4. 4.
    4In this article, we will use this terminology; by intrinsic surface states, we mean surface states characteristic of the “ideal” rearranged surface. The density of these intrinsic surface states should correspond to the total density of surface atoms. The term “extrinsic surface state” will be used for surface states induced by surface defects or impurities. The density of these states will normally correspond to the density of surface defects, imperfections, and impurities.Google Scholar
  5. 5.
    C. A. Mead and W. G. Spitzer, Phys. Rev. 134, A713 (1964); S. Kurten, T. C. McGill and C. A. Mead, Phys. Rev. Lett. 22,1433 (1969).CrossRefGoogle Scholar
  6. 6.
    C. B. Duke, A. Lubinsky, B. W. Lee, and P. Mark, J. Vac. Sci. Technol. 13, 761 (1976); P. Mark, G. Cisneros, M Bonn, A. Kahn, C. B. Duke, G. Patton, and A. R. Lubinsky, J. Vac. Sci. Technol. 14,883 (1977); C. B. Duke, J. Vac. Sci. Technol. 14,870(1977).CrossRefGoogle Scholar
  7. 7.
    A. U. MacRae and G. W. Gobeli, in Semiconductors and Semimetals, Vol. 2 of Physics of 3–5 Compounds, edited by R. K. Willardson and A. C. Beer (Academic, New York, 1966), pp. 115–137; W. A. Harrison, Surf. Sci. 55, 1 (1976).Google Scholar
  8. 8.
    A. Kahn, E. So, P. Mark, C. B. Duke, and R. J. Meyer, J. Vac. Sci. Technol. 15,1223 (1978); B. J. Mrstik, S. Y. Tong, and M. A. Van Hove, J. Vac. Sci. Technol. 16,1258 (1979). C. B. Duke, R. J. Meyer, A. Kahn, E. So, and P. Mark, J. Vac. Sci. Technol. 16,1252 (1979).CrossRefGoogle Scholar
  9. 9.
    D. J Chadi, J. Vac. Sci. Technol. 15,1244 (1978); A. Huijser, J. van Laar, and T. 1. Van Rooy, Phys. Lett. 65A, 335 (1978); J. R. Chelikowsky, S. G. Louie, and M. L. Cohen, Phys. Rev. B 14,4724 (1976).CrossRefGoogle Scholar
  10. 10.
    W. E. Spicer, I. Lindau, J. N. Miller, D. T. Ling, P. Pianetta, P. W. Chye, and C. M. Garner, Physica Scripta 16,388 (1977).CrossRefGoogle Scholar
  11. 11.
    J. Bardeen, Phys. Rev. 71,717 (1947).CrossRefGoogle Scholar
  12. 12.
    V. Heine, Phys. Rev. 138, A1689 (1965).CrossRefGoogle Scholar
  13. 13.
    J. C. Inkson, J. Phys. C5,2599 (1972); C6,1350 (1973), J. Vac. Sci. Technol. 11,943 (1974); S. G. Louie, J. R. Chelikowsky, and M. L. Cohen, Phys. Rev. B15,2154 (1977); J. M. Andrews and J. C. Phillips, Phys. Rev. Lett. 35,56 (1975); C. Tejedor, F. Flores, and E. Louis, J. Phys. CIO, 2163 (1977); E. J. Mele and J. D. Joannopoulos, J. Vac. Sci. Technol. 15,1370 (1978); H. I. Zhang and M: Schluter, J. Vac. Sci. Technol. 15, 1384 (1978); W. A. Goddard III and John J. Barton, J. Vac. Sci. Technol. 15,1273 (1978).Google Scholar
  14. 14.
    P. W. Chye, I. Lindau, P. Pianetta, C. M. Garner, and W. E. Spicer, Phys. Rev. B 17,2682 (1978); P. W. Chye, I. Lindau, P. Pianetta, C. M. Garner, C. Y. Su, and W. E. Spicer, Phys. Rev. B 18,5545 (1978).CrossRefGoogle Scholar
  15. 15.
    I. Lindau, P. W. Chye, C. M. Garner, P. Pianetta, C. Y. Su, and W. E. Spicer, J. Vac. Sci. Technol. 15,1332 (1978).CrossRefGoogle Scholar
  16. 16.
    L. J. Brillson, Phys. Rev. Lett. 40,260 (1978); Phys. Rev. B 18,2431 (1978); J. Vac. Sci. Technol. 15,1378 (1977).CrossRefGoogle Scholar
  17. 17.
    Since, in all cases known to the authors, at least several monolayers of native oxide (i.e., oxide formed from the semiconductor material) occur on the semiconductor before a subsequent deposition of a second insulator film, interface states formed in conjunction with native oxide growth will be of universal importance. Thus, we will concentrate our attention on these states in this paper. However, if the native oxide is successfully removed before the new insulator is deposited, it is anticipated that the same general mechanism of interface state formation will occur due to the difficulty of chemically bonding the insulator to the semiconductor.Google Scholar
  18. 18.
    P. Pianetta, I. Lindau, P. E. Gregory, C. M. Garner, and W. E. Spicer, Surf. Sci. 72,298 (1978); P. Pianetta, I. Lindau, C. M. Garner, and W. E. Spicer, Phys. Rev. B 18,2792 (1978).CrossRefGoogle Scholar
  19. 19.
    P. W. Chye, C. Y. Su, P. Skeath, I. Lindau, and W. E. Spicer (submitted for publication).Google Scholar
  20. 20.
    P. W. Chye, C. Y. Su, I. Lindau, P. Skeath, and W. E. Spicer, J. Vac. Sci. Technol. 16,1191 (1979).CrossRefGoogle Scholar
  21. 21.
    H. H. Wieder, Thin Solid Films (in press), and references therein.Google Scholar
  22. 22.
    22Fusrko Koshiga and Takuo Sugano, Surf. Sci. (in press).Google Scholar
  23. 23.
    H. Hasegawa, T. Sawada, and T. Sakai, Surf. Sci. (in press).Google Scholar
  24. 24.
    A. Shimano, A. Moritani, and J. Nakai, Jpn. J. Appl. Phys. 15, 939 (1977).CrossRefGoogle Scholar
  25. 25.
    C. R. Zeisse, L. J. Messick, and D. L. Lile, J. Vac. Sci. Technol. 14, 957 (1977).CrossRefGoogle Scholar
  26. 26.
    L. G. Meiners, Appl. Phys. Lett, 33, 747 (1978).CrossRefGoogle Scholar
  27. 27.
    H. H. Weider, L. G. Meiners, and D. L. Lile, (private communication).Google Scholar
  28. 28.
    P. Gregory and W. E. Spicer, Phys. Rev. B 12,2370 (1975).CrossRefGoogle Scholar
  29. 29.
    G. W. Gobeli and F. G. Allen, Phys. Rev. 137, A245 (1965); J. H. Dinan, L. K., Galbraith, and T. E. Fisher, Surf. Sci. 26,587 (1971); D. E. Eastman and J. L. Freeouf, Phys. Rev. Lett. 34,1624 (1975).CrossRefGoogle Scholar
  30. 30.
    P. Skeath, W. A. Saperstein, P. Pianetta, I. Lindau, W. E. Spicer, and P. Mark, J. Vac. Sci. Technol. 15,1219 (1978).CrossRefGoogle Scholar
  31. 31.
    P. Mark, P. Pianetta, I. Lindau, and W. E. Spicer, Surf. Sci. 69, 735 (1977).CrossRefGoogle Scholar
  32. 32.
    W. Monch and H. J. Clemens, these proceedings.Google Scholar
  33. 33.
    G. J. Lapeyre, R. J. Smith, J. Knapp, and J. Anderson, J. Physique Colloq. 39, C4–149 (1978).Google Scholar
  34. 34.
    W. Gudat and C. Kunz, Phys. Rev. Lett. 29,169 (1972).CrossRefGoogle Scholar
  35. 35.
    D. E. Eastman and J. L. Freeouf, Phys. Rev. Lett. 33,1601 (1974).CrossRefGoogle Scholar
  36. 36.
    The soft x-ray transitions studied by these methods involve formation of an exciton (see the paper by M. Altarelli, G. Bachelet, atid R. Del Sole, these proceedings) during excitation from the filled Ga 3d core levels into the lowest available empty states. These final states will certainly be the empty surface states provided that they lie in or near the band gap. The problem is more difficult when the empty states lie above the CBM as appears to be the case for the rearranged GaAs (110). However, if any new surface reconstruction moves the surface states into the band gap, this will certainly produce an easily detected reduction in the photon energy necessary to excite the exciton. For metals and oxygen exposures, the surface Fermi level has moved by large amounts before the excitonic transition is removed by the adsorption.Google Scholar
  37. 37.
    I. Lindau, P. Pianetta, W. E. Spicer, and C. M. Garner, Proc. Seventh Intl. Vacuum Congress and the Third Intl. Conf. on Solid Surfaces, Vienna, Austria, 12–16 Sep 1977, p. 615 (R. W. Dobrozemsky, F. G. Rüdenauer, F. P. Viehböck, and A. Breth, eds).Google Scholar
  38. 38.
    P. W. Chye, P. Pianetta, I. Lindau, and W. E. Spicer, J. Vac. Sci. Technol. 14,917(1977).CrossRefGoogle Scholar
  39. 39.
    P. R. Skeath, C. Y. Su, P. W. Chye, P. Pianetta, I. Lindau, and W. E. Spicer, these proceedings; P. R. Skeath, I. Lindau, P. W. Chye, C. Y. Su, and W. E. Spicer, J. Vac. Sci. Technol. 16, 1143 (1979).Google Scholar
  40. 40.
    E. J. Mele and J. D. Joannopoulos, J. Vac. Sci. Technol. 16,1154 (1979).CrossRefGoogle Scholar
  41. 41.
    L. J. Brillson, Phys. Rev. Lett. 42,397 (1979); J. Vac. Sci. Technol. 16,1137 (1979).CrossRefGoogle Scholar
  42. 42.
    For example, the maximum change of electron affinity found on putting Cs on GaAs is about 3.0 eV compared to a maximum change in Fermi level of about 0.7 eV. This is an extreme case, but it illustrates how large the change in electron affinity can be compared to the Fermi level motion at the surface.Google Scholar
  43. 43.
    P. R. Skeath, I. Lindau, P. Pianetta, P. W. Chye, C. Y. Su, and W. E. Spicer (to be published).Google Scholar
  44. 44.
    Patrick Chye, Ph.D. dissertation, Stanford University, 1978 (unpublished).Google Scholar
  45. 45.
    When several monolayers of oxide are grown on GaSb (see Refs. 18 and 44), the oxide position rises to near mid-gap. It is not yet clear whether this represents the oxide surface Fermi level or that at the oxide-semiconductor interface.Google Scholar
  46. 46.
    The usual definition is used for acceptors and donors, i.e., an acceptor is uncharged when containing no electron(s) and a donor is uncharged when it is filled with electron(s).Google Scholar
  47. 47.
    In addition, since the defects are near the surface (we will discuss their position with regard to the surface or interface in more detail later), some interaction with the tunneling wave functions of the metal atoms may also be important.Google Scholar
  48. 48.
    Y. J. Van der Meulen, J. Phys. Chem. Solids 28, 25 (1967).CrossRefGoogle Scholar
  49. 50.
    R.H. Williams, these proceedings.Google Scholar
  50. 51.
    W.E. Spicer, P. Pianetta, I. Lindau, and P.W. Chye, J. Vac. Sci. Technol. 14885 (1987).CrossRefGoogle Scholar
  51. 53.
    Pierro Pianetta, Ph.D. dissertation, Standford University, 1976 (unpublished). Standford Synchrotron Radiation Laboratory rep. 77/17, 1977.Google Scholar
  52. 54.
    C.C. Chang, P.H. Citrin, and B. Schwartz, J. Vac. Sci. Technol. 161388 (1979).Google Scholar
  53. 55.
    Jacques Derrien and Francois Arnaud D’Avitoya, Surf. Sci. 65668 (1977).Google Scholar
  54. 60.
    C.M. Garner, J. Appl. Phys. (in press).Google Scholar
  55. 61.
    C.M. Garner, Ph.D. dissertation, Standford University, 1978 (unpublished).Google Scholar
  56. 63.
    L.F. Wagner and W.E. Spicer, Phys. rev. B 9, 1512 (1974).Google Scholar
  57. 64.
    W.E. Spicer, I. lindau, P. Pianetta, P.W. Chye, and C.M. Garner, I. Lindau, and P. Pianetta, Surf. Sci. (in press).Google Scholar
  58. 65.
    H.H. Wieder (private communication).Google Scholar
  59. 66.
    H. Hasegawa and T. Savada, J. Vac. Sci. Technol. 161483 (1979).Google Scholar
  60. 68.
    K. Heime, Proc. NATO Summer School, “Non-destructive Testing ofGoogle Scholar

Copyright information

© Editorial Jaca Book spa, Milano 1990

Authors and Affiliations

  • W. E. Spicer
    • 1
  • P. W. Chye
    • 1
  • P. R. Skeath
    • 1
  • C. Y. Su
    • 1
  • I. Lindau
    • 1
  1. 1.Stanford Electronics LaboratoriesStanford UniversityCaliforniaUSA

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