Fabrication and simulation of CMOS-compatible photodiodes
Name
243609679-MIT.pdf
Description
Full printable version
Size
20.6 MB
Format
Adobe PDF
Checksum (MD5)
9a70b2ff964962e79136c3805771d502
Author(s)
DiLello, Nicole Ann
Advisor(s)
Judy L. Hoyt.
Date Issued
2008
Publisher
Massachusetts Institute of Technology
Abstract
CMOS-compatible photodiodes are becoming increasinging important devices to study because of their application in combined electronic-photonic systems. They are already used as inexpensive optical transceivers in fiber optic telecommunications systems and they have the potential to be integrated in a number of applications. This thesis focuses on germanium photodiodes to be used in an integrated electronic-photonic analog-to-digital converter. It specifically studies the dark current, responsivity, and frequency response of Ge-on-Si LPCVD-grown diodes that will be used in such a system. It outlines a process that can be used to add metal contacts to pre-existing diodes and discusses characterization procedure. It was found that previously fabricated 50 pm square diodes had leakage current of 0.25 uA at -1 V, but responsivity of -5 mA/W. Diodes with higher leakage current, 1.1 piA at -1 V, had a higher responsivity of -0.5 A/W. Spreading resistance profiles (SRP) indicate that better control of the n-type contact is needed to systematically reproduce these results. Furthermore, spreading resistance analysis demonstrated that elimination of the p-type seed during growth will result in a more abrupt junction, for which simulations predict an improved frequency response. Simulations indicate that removal of the p-type seed and associated autodoping should increase the frequency response from -1.6 GHz to 1-4 GHz. Better control of the n-type profile can further increase the frequency response from '14 GHz to -27 GHz.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.
Includes bibliographical references (p. 65-67).
Subjects
Electrical Engineering and Computer Science.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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