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Physics Seminar

Compound semiconductor quantum dots: the solution of silicon-based laser for silicon photonics

Speaker: Prof Huiyun Liu (University College London)
Date: Wednesday 12 May 2021
Time: 15:00
Venue: Zoom

Silicon is one of the most important semiconductor materials. Although it has been the mainstays for modern electronics, it is not widely used for light emitting sources because bulk silicon is an inefficient emitter. Direct epitaxial growth of III-V compound nanostructures on silicon substrates is one of the most promising candidates for realizing photonic devices on a silicon platform. The major issue of monolithic integration of III-V on group IV platform is the formation of high-density threading dislocations (TDs). The propagation of TDs will cause high ratio of non-radiative recombination centre in III-V epitaxial active region. To stop the TD propagation, defects filter layers (DFLs) formed by InGaAs/GaAs strained-layer superlattices (SLSs) have been applied, which significantly reduce the density of TDs from ~1010/cm2 at the interface between III-V and Si to <10^6/cm^2 in III-V active region.

As a zero-dimensional material, quantum dot (QD) has three-dimensional quantum confinements, which create delta-function like density of states. Therefore, III-V QD lasers have low threshold currents, temperature insensitive operation, and less sensitivity to threading dislocations, which are the ideal candidate to form active region in III-V lasers grown on group IV substrates. High performance QD lasers grown on Si and Ge substrates have been developed since 2011. In this seminar, I will summery the development milestones of InAs/GaAs QD lasers monolithically grown on a Si platform, and predict the further steps on next few years to realize the low-cost silicon-based integrated photonics circuits (IPC) with monolithic III-V QD lasers.

Biography: Professor Liu received the Ph.D from the Institute of Semiconductor, Chinese Academy of Sciences. After receiving his PhD, he joined the EPSRC National Centre for III-V Technologies at University of Sheffield in August 2001. He was responsible for the development of Molecular Beam Epitaxy growth of semiconductor materials for the UK academic and industrial research community. In 2007, he was awarded Royal Society University Research Fellow and started his academic career in the Department of Electronic and Electrical Engineering at UCL as a Senior Lecturer. In 2012, he was promoted as Chair of Semiconductor Photonics.