Hostname: page-component-6bf8c574d5-qdpjg Total loading time: 0 Render date: 2025-02-22T17:00:34.122Z Has data issue: false hasContentIssue false
  • English
  • Français

Dependence of Image Transient Behavior on Operating Parameters of Amorphous Silicon Image Sensors

Published online by Cambridge University Press:  15 February 2011

Koorosh Aflatooni ,
Richard Weisfield ,
Fan Zhong ,
Jon Bornstein ,
Mike Hack  and
Carlos Gomcz
Koorosh Aflatooni
Affiliation:
dpiX, A Xerox New Enterprise Co., Palo Alto, CA
Richard Weisfield
Affiliation:
dpiX, A Xerox New Enterprise Co., Palo Alto, CA
Fan Zhong
Affiliation:
dpiX, A Xerox New Enterprise Co., Palo Alto, CA
Jon Bornstein
Affiliation:
dpiX, A Xerox New Enterprise Co., Palo Alto, CA
Mike Hack
Affiliation:
dpiX, A Xerox New Enterprise Co., Palo Alto, CA
Carlos Gomcz
Affiliation:
dpiX, A Xerox New Enterprise Co., Palo Alto, CA
Get access

Abstract

The growing interests for real-time applications of our amorphous silicon X-ray image sensors requires a better understanding of transient behavior in imaging characteristics. In our pixel structure, which consists of a p-i-n photodiode and an addressing thin film transistor (TFT), the image lag can stem from a number of mechanisms, including charge retention on the photodiode, TFT charge transfer efficiency, and data-line charge sharing. The exact prevailing mechanism depends on the array design and the operating conditions of the sensors. This paper describes the results of our systematic studies on image lag, and its dependence on various operating conditions of the image sensors, such as applied bias, light intensity, frame time, and applied gate voltages. We find that the charge retention in the intrinsic region of the photodiode is an important source of the image lag, and it is correlated to the forward transient characteristics of the diode. This correlation can be explained by the common underlying mechanisms leading to depletion region formation and charge transport through the diode. Furthermore, we notice that the time dependent decay of the image lag, originated mainly from charge retention in the diode, presents power-law time dependence, which is consistent with the release of trapped charges from a continuous distribution of defect states. We also find only a small variation in the image lag, <%3, for a wide range of gate on-periods, 10μs-80μs, and gate on-voltages, 15V- 30V, which indicates an efficient charge transfer by the switching TFT. These results demonstrate that in our devices, the image lag is controlled by the intrinsic defect levels in the a-Si:H photodiode.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 827
Copyright
Copyright © Materials Research Society 1999

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

1) Weisfield, R. L., Hartney, M. A., Schneider, R., Aflatooni, K., and Lujan, R., SPIE Physics of Medical Imaging, in press (1999).Google Scholar
2) Weisfield, R. L., Hartney, M. A., Street, R. A., and Apte, R. B., SPIE Physics of Medical Imaging 3336, p. 444 (1998).Google Scholar
3) Fujieda, I., Nelson, S., Street, R. A., and Weisfield, R. L., IEEE Trans. Nucl. Sci. 39, p. 1056 (1992).Google Scholar
4) Street, R. A., Hydrogenated Amorphous Silicon, Cambridge University Press, London, 1991.Google Scholar
5) Tiedje, T., and Rose, A., Solid State Communication 37, p. 49 (1980).Google Scholar
6) Street, R. A., and Hack, M., Mat. Res. Soc. Symp. Proc. 258, p. 315 (1992).Google Scholar
7) Hack, M., and Street, R. A., J. Appl. Phys. 72, p. 2331 (1992).Google Scholar
8) Han, D., Wang, K., and Silver, M., J. Non-Cryst. Solids 164–166, p. 339 (1993).Google Scholar