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Huiyun Liu

Dr Huiyun Liu

Dr Huiyun Liu

Research Fellow

Interests and expertise (Subject groups)

Grants awarded

Long-wavelength semiconductor quantum-dot materials and devices

Scheme: University Research Fellowship

Organisation: University College London

Dates: Oct 2012-Sep 2015

Value: £312,710.43

Summary: I have been working on two research areas in last 12 months: Si photonics and solar cells. 1. Si photonics: The next critical problem in the evolution of modern information system is to overcome the limitations of metal interconnects. Incorporating photonic components into silicon microelectronics has the potential to overcome this issue while pushing forward the silicon microelectronics beyond the classical CMOS era. Si-based light generation and modulation technologies have been severely limited due to the indirect bandgap of Si. Direct bandgap III-V compounds have robust photonic properties that can be tailored for for many photonic applications. Integrating III-V photonic components with Si microelectronics would thus provide the ideal solution for Si photonics. In my group, the III-V quantum dots (QD) – semiconductor nanosize crystal- have been used to develop III-V QD lasers on Si based on their special properties including low operating current, stable operation at high temperature, and less sensitive to defects. 2. Solar cells: Solar energy seems to be the most viable choice to meet our clean energy demand. The major barrier for the large-scale use of solar energy is the high cost and inadequate efficiencies of existing solar cells. Innovations are needed to harvest incident solar photons with greater efficiency and economical viability. Si-based solar cell modules currently dominate the solar energy market because of their low-cost and long-term reliability, but convert only about 8-20% of the available solar energy. Very high efficiencies (>40%) can be obtained using III-V multi-junction solar cells, which are very expensive. Due to the special properties of nanostructures, high-efficiency III-V solar cells with nanostructures, such as quantum dots and nanowires, could be fabricated on cheap Si substrates. We have been working on the development III-V nanostructures onto silicon substrates for high-efficiency and low-cost solar cells.

Long-wavelength semiconductor quantum-dot materials and devices

Scheme: University Research Fellowship

Organisation: University College London

Dates: Oct 2007-Sep 2012

Value: £525,686.40

Summary: Si microelectronics has been the engine of the modern information for almost 50 years. In our everlasting quest to process more and more data at faster speeds, while using the smallest components the $100 billion silicon industry has successfully overcome many critical issues. The next critical problem in the evolution of modern information system is to overcome the limitations of metal interconnects. Incorporating photonic components into silicon microelectronics has the potential to overcome this issue while pushing forward the silicon microelectronics beyond the classical CMOS era. Although Si-based light generation and modulation technologies have been explored extensively, their practicality has been severely limited due to the indirect bandgap of Si, the significant challenge posed by nature. Direct bandgap III-V compounds have robust photonic properties that can be tailored for III-V emitters operating at various wavelengths with high efficiency, large direct modulation bandwidth, and sufficient optical power output for many photonic applications. Integrating III-V photonic components with Si microelectronics would thus provide the ideal solution for Si photonics. In my group at UCL, the III-V quantum dots – semiconductor nanosize crystal- have been used to develop III-V QD lasers on Si based on their special properties including low operating current and voltage, a high overall efficiency, stable operation at high temperature, and less sensitive to defects. During the last year, continuous-wave quantum-dot lasers on silicon substrates with low room-temperature threshold current density have been first demonstrated at UCL, which paths a way for the long-dreamed III-V/Si integration. In addition, by combining low-cost silicon substrates and high-efficiency III-V solar cells, we developed III-V nanowire solar cells grown on silicon substrates with record high efficiency for nanowire solar cells grown on silicon substrates.

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