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Defects in Semiconductors 

Important Results:

  1. Bond Center Hydrogen
  2. H/D Isotope Effect
  3. Structure Dependent Lifetimes
  4. Hydrogen Bending Modes
  5. Interstitial Oxygen in Si and Ge


>> H/D Isotope Effect

Hydrogen passivation of defects is a standard processing step in the production of metal-oxide-semiconductor (MOS) electronic devices. Devices treated with deuterium (D) have shown transconductance lifetimes 10-50 times longer than H-passivated devices, an effect that has been termed the “giant H/D isotope effect.”

Dissociation of Si-H and Si-D is believed to be caused by ineleastic electron scattering, which excites the bonds to either a dissociative electronic state or to excited vibrational states. The vibrational excitation mechanism has been described by the truncated harmonic oscillator (THO) model. This model describes the Si-H and Si-D bonds as harmonic oscillators, and assumes that the bonds dissociate at a rate R given by the rate of excitation from the highest bound vibrational state |Nmaxñ to the lowest unbound state |Nmax+1ñ. The THO model also provides a simple explanation for the H/D isotope effect. For instance, Nmax for Si-D is ~Ö2 times greater than for Si-H, which would lead to a great reduction in the dissociation rate. Moreover, Si-D modes are usually believed to have shorter lifetimes (T1’s) than the corresponding Si-H modes, which would make the isotope effect even greater.



Against conventional wisdom we find that lifetimes of Si-D modes typically are longer than for the corresponding Si-H modes. However, the inverted isotope dependence of T1 observed for HV·VH(110) implies that this defect and perhaps also Pb:H centers, exhibits much larger differences in Si-D and Si-H dissociation rates than most other H-related defects.

Text Box:


  1. L. C. Feldman, G. Lüpke, N. H. Tolk, Vibrational Lifetimes of Hydrogen and Silicon MOSFET Reliability, Solid State Phenomena 95-96, 2003, pp. 123-28.
  2. M. Budde, G. Lüpke, E. Chen, X. Zhang, N. H. Tolk, L. C. Feldman, E. Tarhan, A. K. Ramdas, M. Stavola, Liftetimes of hydrogen and deuterium related vibrational modes in silicon, Phys. Rev. Lett. 87, 2001, pp. 145501-4.

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>> Next :: Structure Dependent Llifetimes ::

Funding: NSF, DoE, Jeffress Foundation




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