Fanglu Lu

EECS Department, University of California, Berkeley

Technical Report No. UCB/EECS-2017-8

May 1, 2017

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-8.pdf

Using optical signal rather than electrical signal to transmit information on silicon-based computer chips, also known as intra-chip optical interconnect, can potentially boost computation speed and reduce energy consumption. This requires a laser source on silicon, which is a challenging task. Almost all commercial semiconductor lasers are made of III-V material because silicon is an inefficient emitter due to its indirect bandgap. Therefore, integration of III-V laser on silicon is a must towards practical optical interconnect. However, both lattice constant and thermal expansion coefficient mismatch between III-V and silicon fundamentally restricted high quality III-V thin film growth on top of silicon substrates. III-V nanostructures on silicon, on the other hand, can overcome this issue thanks to their small footprint and fully relaxed strain from lattice mismatch. As a result, III-V nanolaser becomes a promising candidate as the on-chip light source for optical interconnect.

In this dissertation, our III-V nanopillar lasers experimentally demonstrate integration capabilities with silicon-based electronics and photonics. The nucleation and growth mechanism of InGaAs and InP nanopillars is first studied with characterization observations, unveiling the reason accounting for the high quality nanopillar. The superior crystal quality, together with unique 3D whispering gallery mode, enables the laser oscillation in as-grown nanopillars. To prove the CMOS compatibility, these nanolasers are monolithically grown onto silicon-based transistor chips, without compromising the electronic performance of chips. In addition, horizontal nanopillar growth is developed to integrate nanolasers with silicon waveguides in an end-fire manner. The coupling between laser and waveguide is prominently observed under photoluminescence experiment, serving as a proof-of-concept for integration with more complicated photonic circuits. To avoid laser emission absorbed by silicon, long wavelength lasers are obtained with InP/InGaAs/InP quantum well nanpillars and three novel optical cavities. Detailed laser modeling is also performed to provide guidance for further laser optimization. For electrical pumping, we also explores methods to make perfect nanopillar diodes. Furthermore, an optical link with nanopillar devices and polymer waveguide is shown to be functional to transmit signals on silicon substrate. With these experimental demonstrations, this III-V nanolaser strategy presents a great potential to achieve on-chip laser source.

Advisors: Constance Chang-Hasnain

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BibTeX citation:

@phdthesis{Lu:EECS-2017-8,
    Author= {Lu, Fanglu},
    Title= {III-V Nanolaser Integration with CMOS Electronics and Silicon Photonics},
    School= {EECS Department, University of California, Berkeley},
    Year= {2017},
    Month= {May},
    Url= {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-8.html},
    Number= {UCB/EECS-2017-8},
    Abstract= {Using optical signal rather than electrical signal to transmit information on silicon-based computer chips, also known as intra-chip optical interconnect, can potentially boost computation speed and reduce energy consumption. This requires a laser source on silicon, which is a challenging task. Almost all commercial semiconductor lasers are made of III-V material because silicon is an inefficient emitter due to its indirect bandgap. Therefore, integration of III-V laser on silicon is a must towards practical optical interconnect. However, both lattice constant and thermal expansion coefficient mismatch between III-V and silicon fundamentally restricted high quality III-V thin film growth on top of silicon substrates. III-V nanostructures on silicon, on the other hand, can overcome this issue thanks to their small footprint and fully relaxed strain from lattice mismatch. As a result, III-V nanolaser becomes a promising candidate as the on-chip light source for optical interconnect.  

In this dissertation, our III-V nanopillar lasers experimentally demonstrate integration capabilities with silicon-based electronics and photonics. The nucleation and growth mechanism of InGaAs and InP nanopillars is first studied with characterization observations, unveiling the reason accounting for the high quality nanopillar. The superior crystal quality, together with unique 3D whispering gallery mode, enables the laser oscillation in as-grown nanopillars. To prove the CMOS compatibility, these nanolasers are monolithically grown onto silicon-based transistor chips, without compromising the electronic performance of chips. In addition, horizontal nanopillar growth is developed to integrate nanolasers with silicon waveguides in an end-fire manner. The coupling between laser and waveguide is prominently observed under photoluminescence experiment, serving as a proof-of-concept for integration with more complicated photonic circuits. To avoid laser emission absorbed by silicon, long wavelength lasers are obtained with InP/InGaAs/InP quantum well nanpillars and three novel optical cavities. Detailed laser modeling is also performed to provide guidance for further laser optimization. For electrical pumping, we also explores methods to make perfect nanopillar diodes. Furthermore, an optical link with nanopillar devices and polymer waveguide is shown to be functional to transmit signals on silicon substrate. With these experimental demonstrations, this III-V nanolaser strategy presents a great potential to achieve on-chip laser source.},
}

EndNote citation:

%0 Thesis
%A Lu, Fanglu 
%T III-V Nanolaser Integration with CMOS Electronics and Silicon Photonics
%I EECS Department, University of California, Berkeley
%D 2017
%8 May 1
%@ UCB/EECS-2017-8
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-8.html
%F Lu:EECS-2017-8