Advertisement

Band-Edge Conduction in Amorphous Semiconductors

  • Don Monroe
Part of the Institute for Amorphous Studies Series book series (IASS)

Abstract

Numerous experiments have shown that the conduction process near the band edges of amorphous semiconductors differs from that in crystals. Three possible explanations for the anomalies have been proposed: long-range potential fluctuations, hopping in band tails, and polaron formation. In this paper the transport energy description will be used to show in a transparent way how band-tail hopping may cause the anomalous transport. Transient measurements provide additional evidence for hopping. In the band-tail-hopping regime, the mobility edge plays no direct role in transport phenomena.

Keywords

Transport Energy Chalcogenide Glass Transport State Amorphous Semiconductor Band Tail 
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.
    N.F. Mott, “Conduction in glasses containing transition metal ions,” J. Non-cryst. Solids 1,1 (1968).ADSCrossRefGoogle Scholar
  2. 2.
    M.H. Cohen, H. Fritzsche, and S.R. Ovshinsky, “Simple band model for amorphous semiconducting alloys,” Phys, Rev. Lett.22,1065 (1969).ADSCrossRefGoogle Scholar
  3. 3.
    T. Tiedje and A. Rose, “A physical interpretation of dispersive transport in disordered semiconductors,” Solid State Commun.37,49 (1981).ADSCrossRefGoogle Scholar
  4. 4.
    J. Orenstein and M. Kastner, “Photocurrent transient spectroscopy: measurement of the density of localized states in a-As2Se3,” Phys. Rev. Lett.48,1421 (1981).ADSCrossRefGoogle Scholar
  5. 5.
    Don Monroe and M.A. Kastner, “Exactly exponential band tail in a glassy semiconductor,” Phys. Rev. B 33,8881 (1986).ADSCrossRefGoogle Scholar
  6. 6.
    C.H. Seager and Rod. K. Quinn, “DC electronic transport in binary arsenic chalcogenide glasses,” Non-cryst. Solids 17,386 (1975).ADSCrossRefGoogle Scholar
  7. 7.
    J.M. Marshall and G.R. Miller, “Field-dependent carrier transport in non-crystalline semiconductors,” Philos. Mag.27,1151 (1973).ADSCrossRefGoogle Scholar
  8. 8.
    David Emin, C.H. Seager, and Rod K. Quinn, “Small-polaron hopping motion in some chalcogenide glasses,” Phys. Rev. Lett.28,813 (1972).ADSCrossRefGoogle Scholar
  9. 9.
    L.H. Robins and M.A. Kastner, “Recombination and excited-state absorption at photoluminescence centres in crystalline and amorphous arsenic triselenide,” Philos. Mag. B 50, 29 (1984).Google Scholar
  10. 10.
    H. Fritzsche, “Optical and electrical energy gaps in amorphous semiconductors,” J. Non-cryst. Solids 6,49 (1971).ADSCrossRefGoogle Scholar
  11. 11.
    F. Boulitrop, D.J. Dunstan, and A. Chenevas-Paule, “New model of the temperature dependence of the 1.4-eVemission tan J of amorplious silicon,” Phys. Rev. B 25, 7860, (1990). ADSCrossRefGoogle Scholar
  12. 12.
    D. J. Dunstan, “New evidence for a fluctuating band-gap in amorphous semiconductors,” J. Phys. C.16,L567 (1983).ADSCrossRefGoogle Scholar
  13. 13.
    T. Skettrup, “Urbach’s rule derived from thermal fluctuations in the band-gap energy,” Phys. Rev. B 18,2622 (1978).ADSCrossRefGoogle Scholar
  14. 14.
    M. Roberts and D.J. Dunstan, “A theory of band-gap fluctuations in amorphous semiconductors,” J. Phys. C 18,5429 (1985).ADSCrossRefGoogle Scholar
  15. 15.
    H. Overhof and W. Beyer, “A model for the electronic transport in hydrogenated amorphous silicon,” Philos. Mag. B 43,433 (1981).CrossRefGoogle Scholar
  16. 16.
    B.I. Shklovskii, “Percolation mechanism of electrical conduction in strong electric fields,” Sov. Phys. Semicond.,13,53 (1979) (translated from Fiz. Tekh. Poluprovodn.13,93 (1979)).Google Scholar
  17. 17.
    G. Pfister, “Pressure-dependent electronic transport in amorphous As2Se3,” Phys. Rev. Lett.33,1474 (1974).ADSCrossRefGoogle Scholar
  18. 18.
    L. Friedman, “Hall conductivity of amorphous semiconductors in the random-phase model,” J. Non-cryst. Solids 6,49 (1971).ADSCrossRefGoogle Scholar
  19. 19.
    A.J. Grant and E.A. Davis “Hopping conduction in amorphous semiconductors,” Solid State Commun.15,563 (1974).ADSCrossRefGoogle Scholar
  20. 20.
    P. Nagels, R. Callaerts, and M. Denayer, “Conduction in extended and localized states in the amorphous system As-Te-Si,” in Amorphous and Liquid Semiconductors,J. Stuke and W. Brenig, eds., Taylor and Francis, London (1974).Google Scholar
  21. 21.
    M. Griinewald and P. Thomas, “A hopping model for activated charge transport in amorphous silicon,” phys. stat. sol. (b) 94,125 (1975). Several years later, I rederived their results, of which I had been unaware, in the context of transient experiments. I would like to apologize for failing to give them proper credit.ADSCrossRefGoogle Scholar
  22. 22.
    B. Movaghar, M. Griinewald, B. Pohlmann, D. Wurtz, and W. Schirmacher, J. Stat. Phys.30,315 (1983).ADSCrossRefGoogle Scholar
  23. 22a.
    B. Movaghar and W. Schirmacher, “On the theory of hopping conductivity in disordered systems,” J. Phys. C.14,859 (1981).ADSCrossRefGoogle Scholar
  24. 22b.
    S. Summerfield and P.N. Butcher, “Analysis of AC and DC hopping conductivity in impurity bands and amorphous semiconductors,” J. Phys. G.16,295 (1983).CrossRefGoogle Scholar
  25. 23.
    Fred W. Schmidlin, “Kinetic theory of hopping transport I. The formalism and its relationship to random walks,” Philos. Mag. B41, 535 (1980).CrossRefGoogle Scholar
  26. 24.
    Don Monroe, “Hopping in exponential band tails,” Phys. Rev. Lett.54,146 (1985).ADSCrossRefGoogle Scholar
  27. 25.
    Don Monroe, Transient Transport and Optical Studies of Chalcogenide Glasses,Ph.D. thesis, Massachusetts Institute of Technology, 1985 (unpublished).Google Scholar
  28. 26.
    G.H. Dohler, “Conductivity, thermopower, and statistical shift in amorphous semiconductors,” Phys. Rev. B. 19,2083 (1979).ADSCrossRefGoogle Scholar
  29. 27.
    Finley R. Shapiro and David Adler, “Electrical conductivity and thermoelectric power in amorphous semiconductors,” Non-cryst. Solids 77&;78 139, (1985).Google Scholar
  30. 28.
    D. Monroe, J. Orenstein, and M.A. Kastner, “Density of states in the gap of a—As2Se3by photocurrent transient spectroscopy,” J. Phys. (Paris),Colloq. 42,C4–559 (1981).CrossRefGoogle Scholar
  31. 29.
    M. Silver, G. Schonherr, and H. Bassler, “Dispersive hopping transport from an exponential distribution of sites,” Phys. Rev. Lett.48,352 (1982).ADSCrossRefGoogle Scholar
  32. 30.
    T. Tiedje, “Information about band tail states from time-of-flight experiments,” in Semiconductors and Semimetals, Vol. 21, Part CJ.I. Pankove, ed. Academic, New York (1984).Google Scholar
  33. 31.
    I.K. Kristensen and J.M. Hvam, “Dispersive transport and trap saturation in doped hydrogenated amorphous silicon,” Solid State Commun.50,845 (1984).ADSCrossRefGoogle Scholar
  34. 32.
    Joseph Orenstein, Transient Photo-induced Optical Absorption and Photoconductivity in Chalcogenide Glasses,Ph.D. thesis, Massachusetts Institute of Technology, 1981 (unpublished).Google Scholar
  35. 33.
    Don Monroe and MA. Kastner, “Photo-induced optical absorption in glassy As2Se3,” in Physics of Disordered Materials,D. Adler, H. Fritzsche, and S. R.Ovshinsky, eds. Plenum, New York (1985).Google Scholar
  36. 34.
    Marc Kastner, “Defects in lone-pair semiconductors. The valence alternation model and new directions,” J. Non-cryst. Solids 35–38,807 (1980).ADSCrossRefGoogle Scholar
  37. 35.
    B.A. Wilson, T.P Kerwin, and J.P. Harbison, “Optical Studies of Thermalization Mechanisms in a-Si:H,” Phys. Rev.31,7953 (1985).ADSCrossRefGoogle Scholar
  38. 36.
    D.J. Dunstan and F. Boulitrop, “Photoluminescence in hydrogenated amorphous silicon,” Phys. Rev. B 30,5945 (1984).ADSCrossRefGoogle Scholar
  39. 37.
    M. Griinewald, B. Movaghar, B. Pohlmann, and D. Wiirtz, “Hopping theory of band-tail relaxation in disordered semiconductors,” Phys. Rev. B 32,8191 (1985).ADSCrossRefGoogle Scholar
  40. 38.
    T.E. Orlowski and H. Scher, “Picosecond photoluminescence: A probe of band-tail thermalization in amorphous semiconductors,” Phys. Rev. Lett.54,254 (1985).ADSCrossRefGoogle Scholar
  41. 39.
    Harvey Scher and Elliot W. Montroll, “Anomalous Transit-time Dispersion in Amorphous Solids,” Phys. Rev. B 12,2455 (1975).ADSCrossRefGoogle Scholar
  42. 40.
    M. Pollak, “On dispersive transport by hopping and by trapping,” Philos. Mag.38, 1157 (1977).ADSCrossRefGoogle Scholar
  43. 41.
    H. Fritzsche, “A review of some electronic properties of amorphous substances,” in Electronic and Structural Properties of Amorphous Semiconductors,P.G. LeCbmber and J.Mort, eds, Clarendon Press, Oxford (1971).Google Scholar

Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • Don Monroe
    • 1
  1. 1.AT&T Bell LaboratoriesMurray HillUSA

Personalised recommendations