Hostname: page-component-7857688df4-mqpdw Total loading time: 0 Render date: 2025-11-19T14:08:40.289Z Has data issue: false hasContentIssue false
  • English
  • Français

Hole Drift-Mobility Measurements in Contemporary Amorphous Silicon

Published online by Cambridge University Press:  01 February 2011

S. Dinca ,
G. Ganguly ,
Z. Lu ,
E. A. Schiff ,
V. Vlahos ,
C. R. Wronski  and
Q. Yuan
S. Dinca
Affiliation:
Department of Physics, Syracuse University, Syracuse, NY 13244-1130
G. Ganguly
Affiliation:
Department of Physics, Syracuse University, Syracuse, NY 13244-1130
Z. Lu
Affiliation:
BP Solar, Inc., Toano, Virgina 23168
E. A. Schiff
Affiliation:
Department of Physics, Syracuse University, Syracuse, NY 13244-1130
V. Vlahos
Affiliation:
BP Solar, Inc., Toano, Virgina 23168
C. R. Wronski
Affiliation:
BP Solar, Inc., Toano, Virgina 23168
Q. Yuan
Affiliation:
Department of Physics, Syracuse University, Syracuse, NY 13244-1130 Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 18702
Get access

Abstract

We present hole drift-mobility measurements on hydrogenated amorphous silicon from several laboratories. These temperature-dependent measurements show significant variations of the hole mobility for the differing samples. Under standard conditions (displacement/field ratio of 2×10-9 cm2/V), hole mobilities reach values as large as 0.01 cm2/Vs at room-temperature; these values are improved about tenfold over drift-mobilities of materials made a decade or so ago. The improvement is due partly to narrowing of the exponential bandtail of the valence band, but there is presently little other insight into how deposition procedures affect the hole drift-mobility.

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.)

Article purchase

Temporarily unavailable

References

1. Wang, Qi, Antoniadis, H., Schiff, E.A., and Guha, S., Phys. Rev. B, 47, 9435 1993.Google Scholar
2. Gu, Q., Wang, Q., Schiff, E.A., Li, Y.-M., and Malone, C.T., J. Appl. Phys. 76, 2310 (1994).Google Scholar
3. Ganguly, G. and Matsuda, A., J. Non-Cryst. Solids 198-200, 1003 (1996); Ganguly's hole drift-mobility measurements are consistent with later measurements on the same materials by P. Rao at Syracuse University (private communication).Google Scholar
4. Brinza, M., Adriaennsens, G. J., Iakoubovskii, K., Stesmans, A., Kessels, W. M. M., Smets, A. H. M, Sanden, M. C. M. van de, J. Non-Cryst. Solids 299-302, 420 (2002). In this paper, mobilities for several samples with varying thickness are reported for a common displacement-field ratio about L/E =9.5×10-9 cm2/V. The fact that these mobilities are essentially the same for the three differing thicknesses is a very nice experimental confirmation that the displacement/field ratio determines drift-mobilities for a given type of material. These authors use a definition of the drift-mobility that yields values twice as large as the definition used in the present paper. In preparing Figure 1, we corrected for the lower value of L/E =2×10-9 cm2/V by using the result for dispersive transport μD ∞ (L/E)1-1/α [1]. The authors gave a room-temperature dispersion parameter of 0.7; for other temperatures, we assumed the dispersion parameter to be proportional to the absolute temperature, as expected for bandtail multiple-trappingGoogle Scholar
5.The constant K is based on two sources. One is the expression connecting the transient photocurrent before carrier transit to the multiple trapping parameters (Schiff, E. A., Phys. Rev. B 24, 6189 1981 – equation (6)); after integration, this expression yields: where α = kT/EV, NV is the effective density of states of the valence band, and gV 0 is the density-of-states (cm-3eV-1) for the valence bandtail at the upper edge of the valence band. The second source is the relationship NV/gV0 = kT (1-α) that obtains from the assumption that the valence band edge lies within the exponential bandtail (E. A. Schiff, Solar Energy Materials and Solar Cells, in press (2003).Google Scholar
6. Gu, Q., Schiff, E.A., Chevrier, J.-B., and Equer, B., in Amorphous Silicon Technology - 1993, edited by Schiff, E. A., et al (Materials Research Society, Symposium Proceedings Vol. 297, Pittsburgh, 1993), pp. 425–430.Google Scholar