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Title: | Germanium on Silicon Near-Infrared Photodetectors |
Authors: | Sorianello, Vito |
Tutor: | Colace, Lorenzo |
Issue Date: | 23-Apr-2010 |
Publisher: | Università degli studi Roma Tre |
Abstract: | In recent years, the of Germanium on Silicon approach has been recognized
as the best alternative to the well-established III-V technology for the fabrication of high performance near-infrared photodetectors. Recent results
demonstrate that Ge heteroepitaxy on Si is by now mature to compete with
standard III-V devices. Unfortunately, the integration of Ge-on-Si technology in standard CMOS process flows is still an open challenge due to the
sophisticated growth techniques as well as the high thermal budget involved.
This work proposes an alternative approach to the growth of Ge on Si for
NIR optoelectronics applications.
The first chapter introduces NIR detection for optical communication systems, with particular emphasis on Ge as a suitable material for the monolithic integration into NIR photodetectors on a Si platform.
In the second chapter, the deposition process is described. Ge is deposited
on Si by thermal evaporation, a very simple and low temperature (300◦ C )
technique suitable for both streamline process and back-end monolithic integration of Ge on Si CMOS electronics. Material characterization, both
morphological and electrical, is also discussed. Raman and X-Ray analysis,
as well as Transmission Electron Microscopy evidenced that Ge is epitaxially grown in a monocrystalline form with a high dislocation density. Hall
measurements demonstrated high unintentional p -type doping (1017 ÷ 1018
cm−3 ) associated to the acceptor-like levels due to the large defect density.
The transport and detection properties of evaporated Ge on Si heterojunctions are presented in the third chapter. Results demonstrated a trapassisted conduction mechanism explained by energy band pinning at the
Ge/Si interface. The NIR detection properties were also investigated by
illumination at normal incidence. The high doping together with the short
diffusion length were found to drastically limit the responsivity of normal
incidence devices.
The last part of this work is dedicated to the design and fabrication of
optimized NIR photodetector and their integration on SOI optical chips.
Waveguide photodetectors (WPD) were fabricated to take advantage from
the distributed absorption of light in guiding structures. WPD exhibit very
promising performance with typical responsivities exceeding 0.2 A/W at 1
V reverse bias and 1.55 µm wavelength. These devices were monolithically
integrated on SOI optical chips for the realization of channel monitors. The
integrated devices exhibit very promising performance, with sensitivity of
10 nW and good linearity over about four orders of magnitude. ...more |
URI: | http://hdl.handle.net/2307/663 |
Appears in Collections: | X_Dipartimento di Ingegneria elettronica T - Tesi di dottorato
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Germanium on Silicon Near-Infrared Photodetectors.pdf | | 47.22 MB | Adobe PDF | | |
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