Abstract

With the recent development of an electropolishing technique for producing optically smooth and flat surfaces with a minimum amount of surface damage, a quantitative study of the influence of surface damage and lattice disorder on the optical properties of semiconductors has become possible. In this investigation precise absolute specular reflectance measurements at normal incidence are reported for electropolished and mechanically polished germanium single crystals and for amorphous and polycrystalline germanium films in the 2650-10 000-Å wavelength range. The highest reflectance maxima and considerable structure were exhibited by the electropolished sample. Splitting of the 2.1-eV peak, which had previously been reported only for etched samples, was observed, and shoulders at 3.25 and 2.47-eV were found. The latter shoulder has apparently not been reported previously. The wavelength at which the 2.1-eV peak occurred shifted for the mechanically polished single crystal and for the polycrystalline film and disappeared entirely for the amorphous film. However the 4.4-eV peak, although changing greatly in magnitude, occurred at the same wavelength for all the samples tested. The results of the experiment show that the optical properties of this material are a strong function of the lattice disorder present and emphasize the importance of adequate sample preparation techniques if meaningful optical measurements are to be made.

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  1. T. M. Buck, The Surface Chemistry of Metals and Semiconductors (John Wiley & Sons, Inc., New York, 1959), p. 107.
  2. The skin depth is sometimes defined as the distance beneath the surface at which the intensity of the incident light falls to 1/e of its initial value (see Ref. 3). However, since the field acting at the lattice sites in the crystal is determined by the amplitude of the E vector rather than the intensity, the measure of the distance from the surface at which the electromagnetic disturbance acts is more properly an amplitude function. The two definitions of skin depth differ by a factor of 2.
  3. F. Seitz, The Modern Theory of Solids (McGraw-Hill Book Company, Inc., New York, 1940), p. 642.
  4. R. J. Archer, Phys. Rev. 110, 354 (1958).
  5. J. R. Beattie and G. K. T. Conn, Phil. Mag. 46, 989 (1955).
  6. T. M. Donovan and B. O. Seraphin, J. Electrochem. Soc. 109, 877 (1962).
  7. The sources for these boules were Semimetals, Inc., Westbury, Long Island, New York, and Semi-Elements, Inc., Saxonburg, Pennsylvania.
  8. Tergidal, nonionic detergent, NP44, obtained from Union Carbide Chemicals Company, New York, 17, New York.
  9. No. 1800 lapmaster abrasive obtained from the Crane Packing Company, Morton Grove, Illinois, was used for the lapping operations.
  10. Polishing wheel and materials were obtained from Buehler, Ltd., Evanston, Illinois: Microcloth, Cat. No. 1576; Metadi fluid, Cat. No. 1542-2SS; polishing compound, Cat. No. 1544-AB.
  11. The electrolyte used consisted of KOH dissolved in Buehler Metadi fluid (50 g KOH, 250 ml fluid).
  12. G. R. Booker and R. Stickler, J. Electrochem. Soc. 109, 1167 (1962).
  13. H. E. Bennett, Jean M. Bennett, and E. J. Ashley, J. Opt. Soc. Am. 52, 1245 (1962).
  14. H. E. Bennett and W. F. Koehler, J. Opt. Soc. Am. 50, 1 (1960).
  15. H. R. Philipp and E. A. Taft, Phys. Rev. 113, 1002 (1959).
  16. H. E. Bennett and J. O. Porteus, J. Opt. Soc. Am. 51, 123 (1961).
  17. H. Ehrenreich, H. R. Philipp, and J. C. Phillips, Phys. Rev. Letters 8, 59 (1962).
  18. W. G. Spitzer and H. Y. Fan, Phys. Rev. 106, 882 (1957).
  19. If the correction for the increasing surface roughness present in films deposited at higher temperatures was not made, the observed reflectance maximum appeared to shift to longer wavelengths.
  20. J. Tauc and E. Antoncik, Phys. Rev. Letters 5, 253 (1960).
  21. L. M. Roth and B. Lax, Phys. Rev. Letters 3, 217 (1959).
  22. M. Cardona and H. S. Sommers, Jr., Phys. Rev. 122, 1382 (1961).
  23. H. R. Philipp, W. C. Dash, and H. Ehrenreich, Phys. Rev. 127, 762 (1962).
  24. J. C. Phillips, J. Phys. Chem. Solids 12, 208 (1960).
  25. V. S. Vavilov, A. A. Gippius, and M. M. Gorschkov, Zh. Tekhn. Fiz. 28, 254 (1958) [Engl. Transl. Soviet Phys.—Tech. Phys. 3, 230 (1958)].
  26. H. J. Queisser, J. Appl. Phys. 32, 1776 (1961).

Antoncik, E.

J. Tauc and E. Antoncik, Phys. Rev. Letters 5, 253 (1960).

Archer, R. J.

R. J. Archer, Phys. Rev. 110, 354 (1958).

Ashley, E. J.

H. E. Bennett, Jean M. Bennett, and E. J. Ashley, J. Opt. Soc. Am. 52, 1245 (1962).

Beattie, J. R.

J. R. Beattie and G. K. T. Conn, Phil. Mag. 46, 989 (1955).

Bennett, H. E.

H. E. Bennett and W. F. Koehler, J. Opt. Soc. Am. 50, 1 (1960).

H. E. Bennett, Jean M. Bennett, and E. J. Ashley, J. Opt. Soc. Am. 52, 1245 (1962).

H. E. Bennett and J. O. Porteus, J. Opt. Soc. Am. 51, 123 (1961).

Bennett, Jean M.

H. E. Bennett, Jean M. Bennett, and E. J. Ashley, J. Opt. Soc. Am. 52, 1245 (1962).

Booker, G. R.

G. R. Booker and R. Stickler, J. Electrochem. Soc. 109, 1167 (1962).

Buck, T. M.

T. M. Buck, The Surface Chemistry of Metals and Semiconductors (John Wiley & Sons, Inc., New York, 1959), p. 107.

Cardona, M.

M. Cardona and H. S. Sommers, Jr., Phys. Rev. 122, 1382 (1961).

Conn, G. K. T.

J. R. Beattie and G. K. T. Conn, Phil. Mag. 46, 989 (1955).

Dash, W. C.

H. R. Philipp, W. C. Dash, and H. Ehrenreich, Phys. Rev. 127, 762 (1962).

Donovan, T. M.

T. M. Donovan and B. O. Seraphin, J. Electrochem. Soc. 109, 877 (1962).

Ehrenreich, H.

H. R. Philipp, W. C. Dash, and H. Ehrenreich, Phys. Rev. 127, 762 (1962).

H. Ehrenreich, H. R. Philipp, and J. C. Phillips, Phys. Rev. Letters 8, 59 (1962).

Fan, H. Y.

W. G. Spitzer and H. Y. Fan, Phys. Rev. 106, 882 (1957).

Gippius, A. A.

V. S. Vavilov, A. A. Gippius, and M. M. Gorschkov, Zh. Tekhn. Fiz. 28, 254 (1958) [Engl. Transl. Soviet Phys.—Tech. Phys. 3, 230 (1958)].

Gorschkov, M. M.

V. S. Vavilov, A. A. Gippius, and M. M. Gorschkov, Zh. Tekhn. Fiz. 28, 254 (1958) [Engl. Transl. Soviet Phys.—Tech. Phys. 3, 230 (1958)].

Koehler, W. F.

H. E. Bennett and W. F. Koehler, J. Opt. Soc. Am. 50, 1 (1960).

Lax, B.

L. M. Roth and B. Lax, Phys. Rev. Letters 3, 217 (1959).

Philipp, H. R.

H. R. Philipp, W. C. Dash, and H. Ehrenreich, Phys. Rev. 127, 762 (1962).

H. Ehrenreich, H. R. Philipp, and J. C. Phillips, Phys. Rev. Letters 8, 59 (1962).

H. R. Philipp and E. A. Taft, Phys. Rev. 113, 1002 (1959).

Phillips, J. C.

H. Ehrenreich, H. R. Philipp, and J. C. Phillips, Phys. Rev. Letters 8, 59 (1962).

J. C. Phillips, J. Phys. Chem. Solids 12, 208 (1960).

Porteus, J. O.

H. E. Bennett and J. O. Porteus, J. Opt. Soc. Am. 51, 123 (1961).

Queisser, H. J.

H. J. Queisser, J. Appl. Phys. 32, 1776 (1961).

Roth, L. M.

L. M. Roth and B. Lax, Phys. Rev. Letters 3, 217 (1959).

Seitz, F.

F. Seitz, The Modern Theory of Solids (McGraw-Hill Book Company, Inc., New York, 1940), p. 642.

Seraphin, B. O.

T. M. Donovan and B. O. Seraphin, J. Electrochem. Soc. 109, 877 (1962).

Sommers, Jr., H. S.

M. Cardona and H. S. Sommers, Jr., Phys. Rev. 122, 1382 (1961).

Spitzer, W. G.

W. G. Spitzer and H. Y. Fan, Phys. Rev. 106, 882 (1957).

Stickler, R.

G. R. Booker and R. Stickler, J. Electrochem. Soc. 109, 1167 (1962).

Taft, E. A.

H. R. Philipp and E. A. Taft, Phys. Rev. 113, 1002 (1959).

Tauc, J.

J. Tauc and E. Antoncik, Phys. Rev. Letters 5, 253 (1960).

Vavilov, V. S.

V. S. Vavilov, A. A. Gippius, and M. M. Gorschkov, Zh. Tekhn. Fiz. 28, 254 (1958) [Engl. Transl. Soviet Phys.—Tech. Phys. 3, 230 (1958)].

Other

T. M. Buck, The Surface Chemistry of Metals and Semiconductors (John Wiley & Sons, Inc., New York, 1959), p. 107.

The skin depth is sometimes defined as the distance beneath the surface at which the intensity of the incident light falls to 1/e of its initial value (see Ref. 3). However, since the field acting at the lattice sites in the crystal is determined by the amplitude of the E vector rather than the intensity, the measure of the distance from the surface at which the electromagnetic disturbance acts is more properly an amplitude function. The two definitions of skin depth differ by a factor of 2.

F. Seitz, The Modern Theory of Solids (McGraw-Hill Book Company, Inc., New York, 1940), p. 642.

R. J. Archer, Phys. Rev. 110, 354 (1958).

J. R. Beattie and G. K. T. Conn, Phil. Mag. 46, 989 (1955).

T. M. Donovan and B. O. Seraphin, J. Electrochem. Soc. 109, 877 (1962).

The sources for these boules were Semimetals, Inc., Westbury, Long Island, New York, and Semi-Elements, Inc., Saxonburg, Pennsylvania.

Tergidal, nonionic detergent, NP44, obtained from Union Carbide Chemicals Company, New York, 17, New York.

No. 1800 lapmaster abrasive obtained from the Crane Packing Company, Morton Grove, Illinois, was used for the lapping operations.

Polishing wheel and materials were obtained from Buehler, Ltd., Evanston, Illinois: Microcloth, Cat. No. 1576; Metadi fluid, Cat. No. 1542-2SS; polishing compound, Cat. No. 1544-AB.

The electrolyte used consisted of KOH dissolved in Buehler Metadi fluid (50 g KOH, 250 ml fluid).

G. R. Booker and R. Stickler, J. Electrochem. Soc. 109, 1167 (1962).

H. E. Bennett, Jean M. Bennett, and E. J. Ashley, J. Opt. Soc. Am. 52, 1245 (1962).

H. E. Bennett and W. F. Koehler, J. Opt. Soc. Am. 50, 1 (1960).

H. R. Philipp and E. A. Taft, Phys. Rev. 113, 1002 (1959).

H. E. Bennett and J. O. Porteus, J. Opt. Soc. Am. 51, 123 (1961).

H. Ehrenreich, H. R. Philipp, and J. C. Phillips, Phys. Rev. Letters 8, 59 (1962).

W. G. Spitzer and H. Y. Fan, Phys. Rev. 106, 882 (1957).

If the correction for the increasing surface roughness present in films deposited at higher temperatures was not made, the observed reflectance maximum appeared to shift to longer wavelengths.

J. Tauc and E. Antoncik, Phys. Rev. Letters 5, 253 (1960).

L. M. Roth and B. Lax, Phys. Rev. Letters 3, 217 (1959).

M. Cardona and H. S. Sommers, Jr., Phys. Rev. 122, 1382 (1961).

H. R. Philipp, W. C. Dash, and H. Ehrenreich, Phys. Rev. 127, 762 (1962).

J. C. Phillips, J. Phys. Chem. Solids 12, 208 (1960).

V. S. Vavilov, A. A. Gippius, and M. M. Gorschkov, Zh. Tekhn. Fiz. 28, 254 (1958) [Engl. Transl. Soviet Phys.—Tech. Phys. 3, 230 (1958)].

H. J. Queisser, J. Appl. Phys. 32, 1776 (1961).

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