ZnO Nanowire UV Photodetectors with High Internal Gain

C. Soci,† A. Zhang,† B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, and D. Wang*
Department of Electrical and Computer Engineering, Jacobs School of Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0407
Nano Lett., 2007, 7 (4), pp 1003–1009
DOI: 10.1021/nl070111x
Publication Date (Web): March 15, 2007
Copyright © 2007 American Chemical Society
†

 These authors contributed equally to this work.

,
*

 Author to whom the correspondence should be addressed. E-mail:  dwang@ece.ucsd.edu.

Abstract

Abstract Image

ZnO nanowire (NW) visible-blind UV photodetectors with internal photoconductive gain as high as G 108 have been fabricated and characterized. The photoconduction mechanism in these devices has been elucidated by means of time-resolved measurements spanning a wide temporal domain, from 10-9 to 102 s, revealing the coexistence of fast (τ 20 ns) and slow (τ 10 s) components of the carrier relaxation dynamics. The extremely high photoconductive gain is attributed to the presence of oxygen-related hole-trap states at the NW surface, which prevents charge-carrier recombination and prolongs the photocarrier lifetime, as evidenced by the sensitivity of the photocurrrent to ambient conditions. Surprisingly, this mechanism appears to be effective even at the shortest time scale investigated of t < 1 ns. Despite the slow relaxation time, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products (GB) higher than 10 GHz. The high gain and low power consumption of NW photodetectors promise a new generation of phototransistors for applications such as sensing, imaging, and intrachip optical interconnects.

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History

  • Published In Issue April 11, 2007
  • Received January 15, 2007
    Revised Manuscript Received February 26, 2007

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