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.