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Integration of Thin Film Microscale III V Lasers onto Si_Grace Pakeltis_2
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Transcript of Integration of Thin Film Microscale III V Lasers onto Si_Grace Pakeltis_2
Conclusions
• In the future, this process can be implemented in
manufacturing since it is similar to processes already used.
• Other photonic components, like modulators through butt
coupling strategies and on-chip waveguides, can have III-V
lasers also integrated.
Method
• Lasers are grown on a GaAs baser with a 1μm sacrificial layer of
AL0.95Ga0.05As.
• A ~3μm layer of photoresist is applied to create anchors that will
allow the lasers to be protected and lightly attached to the
substrate when undercut.
• Transfer lasers using a soft printing process utilizing a
polydimethylsiloxane (PDMS) stem.
• Adhere the lasers onto the Si base using an In/Ag eutectic alloy
(97%In+3%Ag,Indalloy290, by Indium Corp.) and a thin-film of
gold (Au 100nm).
Introduction
• Silicon complementary metal-oxide-semiconductors have led the
integrated circuit industry in the past but have reached their
performance limit; therefore, an alternative semiconductor must
be found.
• Mismatched lattice and thermal conductivities cause difficulties
when fully integrating III-V lasers onto Si based platforms.
.
Experimental Results
• The GaAs laser (dimensions 400μm x 100μm, thickness 5.8μm) was able to be fully
integrated onto Si without losing its optoelectronic properties.
• Due to the strain induced splitting of the heavy/light hold bands, the emitted light from the
lasers is primarily TE polarized.
• The laser printed on the In/Ag interface exhibited the lowest temperature during
operation. The SU-8 interface experienced the highest temperature of the interfaces.
• The maximum temperature of the SU-8 interface is dependent on the thickness of the
layer. The In/Ag surface temperature is independent of the thickness of the layer.
Results
• The lasing threshold of the In/Ag interface (~43mA) is very
similar to that of the GaAs substrate which allows the laser to
have similar light intensity as the original laser. The SU-8
interface, however, has a much higher lasing threshold which
restricts light emission.
• Both the In/Ag interface and the original substrate emit
wavelengths centered about 820nm showing that there is no
loss of emission due to thermal degradation.
The graph above shows the maximum
temperatures reached on the surfaces for
the lasers depending on the interface
layer thickness.
Schematic illustration of the soft printing process using a
PDMS stem and then printed onto the Si substrate with
the In/Ag alloy paste.
Optical
micrograph (top
view) of lasers
attached to the
original GaAs
substrate. Some
of the lasers have
been removed
using the PDMS
stamp.
Cross sectional
schematic of a
GaAs based
laser with a
Al0.95Ga0.05As
sacrificial layer.
The graph shows
output light power
as a function of
current (CW
operation). The
plots are offset for
the illustration.
The diagram shows temperature
distributions for lasers with
different interfaces when injected
with 0.15W of electric power
Integration of Thin-Film Microscale III-V Lasers onto Si
Grace Pakeltis1, Dr. Xing Sheng1, Cedric Robert2, Shuodao Wang3, Brian Corbett2, Dr. John Rogers1 1Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign
2Tyndall National Institute, Univeristy College Cork, Lee Maltings, Cork, Ireland 3Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK
Introduction
Method
Results Cont.
Conclusion
Results
The graph shows
the emission
spectrum of the
laser printed with
the In/Ag interface
and the original
GaAs substrate at
a current above
the lasing
threshold.
Top view SEM image of GaAs lasers
integrated onto Si Cross sectional SEM image of
GaAs laser with In/Ag alloy
interface
Calculated
electric field
intensity, |E|2
show the TE
mode at 820nm.