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Nonlocal effects in thin 4H-SiC UV avalanche photodiodes

Ng, B.K., David, J.P.R., Tozer, R.C., Rees, G.J., Yan, F., Zhao, J.H. and Weiner, M. (2003) Nonlocal effects in thin 4H-SiC UV avalanche photodiodes. IEEE Transactions on Electron Devices, 50 (8). pp. 1724-1732. ISSN 0018-9383


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The avalanche multiplication and excess noise characteristics of 4H-SiC avalanche photodiodes with i-region widths of 0.105 and 0.285 mum have been investigated using 230-365-nm light, while the responsivities of the photodiodes at unity gain were examined for wavelengths up to 375 nm. Peak unity gain responsivities of more than 130 mA/W at 265 nm, equivalent to quantum efficiencies of more than 60%, were obtained for both structures. The measured avalanche characteristics show, that beta > alpha and that the beta/alpha ratio remains large even in thin 4H-SiC avalanche regions. Very low excess noise, corresponding to k(eff) < 0.15 in the local noise model, where k(eff) = alpha/beta(beta/alpha) for hole (electron) injection, was measured with 365-nm light in both structures. Modeling the experimental results using a simple quantum efficiency model and a nonlocal description yields effective ionization threshold energies of 12 and 8 eV for electrons and holes, respectively, and suggests that the dead space in 4H-SiC is soft. Although dead space is important, pure hole injection is still required to ensure low excess noise in thin 4H-SiC APDs owing to beta/alpha ratios that remain large, even at very high fields.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright © 2003 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: avalanche multiplication, avalanche photodiodes (APDs), breakdown voltage, dead space, impact ionization, ionization coefficients, nonlocal effects
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Electronic and Electrical Engineering (Sheffield)
Depositing User: Sherpa Assistant
Date Deposited: 19 Dec 2005
Last Modified: 07 Jun 2014 02:50
Published Version: http://dx.doi.org/10.1109/TED.2003.815144
Status: Published
Refereed: Yes
Identification Number: 10.1109/TED.2003.815144
URI: http://eprints.whiterose.ac.uk/id/eprint/898

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