Hostname: page-component-848d4c4894-hfldf Total loading time: 0 Render date: 2024-05-22T15:07:47.952Z Has data issue: false hasContentIssue false
  • English
  • Français

Identification of the Dominant Electron Deep Trap in a-Si:H: A Critical Test of the Defect Pool vs. Defect Relaxation Pictures

Published online by Cambridge University Press:  15 February 2011

Daewon Kwon  and
J. David Cohen
Daewon Kwon
Affiliation:
Department of Physics and Materials Science Institute, University of Oregon, Eugene, OR 97403
Get access

Abstract

Modulated photocurrent (MPC) measurements in intrinsic a-Si:H reveal a prominent band of electron deep traps with a thermal emission energy near 0.6eV. We have identified this defect band by directly comparing MPC and ESR spectra for both an intrinsic and a lightly n-type doped sample for a various metastable states such that the Fermi level, EF, ranges from less than 0.5eV to more than 0.7eV below Ec. This comparsion unambiguously demonstrates that the MPC band arises from the Do charge state of the defects (specifically, the D−&Do transition). This identification is also confirmed when the quasi-Fermi level is varied by the application of light bias even though the peak emission rate from the MPC defect band is changed by more than a factor of 100. These observations specifically rule out the possibility of large populations of charged defects in intrinsic samples predicted by proponents of the defect pool model. Instead, observed behaviors have a natural explanation in terms of a defect relaxation process.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 467: Symposium A – Amorphous and Microcrystalline Silicon Technology - 1997 , 1997 , 197
Copyright
Copyright © Materials Research Society 1997

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Powell, M.J. and Deane, S.C., Phys. Rev. B48, 10815 (1993).Google Scholar
2. Schumm, G., Phys. Rev. B49, 2427 (1994).Google Scholar
3. Zhong, F. and Cohen, J.D., Phys. Rev. Lett. 71, 597 (1993).Google Scholar
4. Oheda, H., J. Appl. Phys. 52, 6693 (1981).Google Scholar
5. Schumm, G. and Bauer, G.H., Phys. Rev. B39, 5311 (1989).Google Scholar
6. Brüggemann, R., Main, C., Berkin, J., and Reynolds, S., Philos. Mag. B62, 29 (1990).Google Scholar
7. Hattori, K., Niwano, Y., Okamoto, H., and Hamakawa, Y., J. Non-Cryst. Solids 137&138, 363 (1991).Google Scholar
8. Han, D., Melcher, D.C., Schiff, E.A., and Silver, M., Phys. Rev. B48, 8658 (1993).Google Scholar
9. Longeaud, C. and Kleider, J.P., Phys. Rev. B53, 16133 (1996).Google Scholar
10. Cohen, J.D. and Zhong, Fan, J. Non-Cryst. Solids 198–200, 512 (1996).Google Scholar
11. Michelson, C.E., Gelatos, A.V., and Cohen, J.D., Appl. Phys. Lett. 47, 412 (1985).Google Scholar
12. See, for example, Unold, T., Hautala, J., and Cohen, J.D., Phys. Rev. B50, 16985 (1994).Google Scholar
13. Such dopant activation is believed to occur, but only when the Fermi level is shallower than about 0.4eV below Ec. See Cohen, J.D. and Leen, T.M., in Amorphous Silicon Materials and Solar Cells, ed. by Stafford, B.L. (AIP Conf. Proc. 234, New York, 1991), pp. 91–97; and,Google Scholar
Okushi, H., Orita, N., Arai, K., and Tanaka, K., J. Non-Cryst. Solids 137&138, 175 (1991).Google Scholar