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Impact ionization of excitons in Ge and Si

Smith, D. L. and Pan, D. S. and McGill, T. C. (1975) Impact ionization of excitons in Ge and Si. Physical Review B, 12 (10). pp. 4360-4366. ISSN 0163-1829.

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A charged free carrier in an applied electric field may pick up enough energy from the field to allow it to impact ionize an excition. For this to occur, the carrier must have an energy greater than the exciton binding energy. At low temperatures (T<~10°K in Ge and T<~30°K in Si) and modest electric fields (E∼2 V/cm in pure Ge and E∼20 V/cm in pure Si), the energy of a significant number of carriers exceed this threshold energy. Once this happens, the impact-ionization process can change the relative concentration of excitons and free carriers; the equilibrium law of mass action is no longer satisfied. Calculations of exciton concentration (for fixed carrier concentration) as a function of temperature and applied-field strength show that a sudden drop in exciton concentration occurs when electric fields exceed a temperature-dependent critical field.

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Additional Information:©1975 The American Physical Society. Received 23 June 1975. We thank C. Jacoboni for sending us his unpublished Monte Carlo calculations of the electron distribution function in Si and C. Canali, A. Loria, F. Nava, and G. Ottaviani for sending us electron drift-velocity measurements in Si and Ge prior to publication. We thank V. Marrello, R.B. Hammond, M. Chen, and J.W. Mayer for valuable conversations on low-temperature double-injection experiments. Work supported in part by the Office of Naval Research under Contract No. N00014-67-A-0094-0036. [T.C.M. was an] Alfred P. Sloan Foundation Fellow.
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ID Code:8501
Deposited By: Tony Diaz
Deposited On:16 Aug 2007
Last Modified:26 Dec 2012 09:39

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