University of Birmingham > Talks@bham > Condensed Matter Physics Seminars > Silicon-based Epitaxy for Photonics

Silicon-based Epitaxy for Photonics

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  • UserProf. David Leadley, University of Warwick
  • ClockFriday 02 March 2012, 14:00-15:00
  • HousePhysics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

Silicon photonics promises to unite the high speed data transmission of optics with the highly developed processing of silicon electronics. Combining the optical and electronic functions on a single chip and benefitting from the economies of scale inherent in silicon manufacturing should lead to major advances in consumer electronics. However, one first needs to efficiently generate, manipulate and detect light in silicon based materials, which is complicated by the indirect band gap and inversion symmetry of silicon. Significant progress has been made by academic groups and major semiconductor companies using just silicon devices; in this talk I will discuss how Ge can be introduced onto Si through epitaxy and what advantages that can bring.

The quantum-confined Stark effect (QCSE) is arguably the dominant technology for modulation in III -V optoelectronic systems. We have grown Ge/SiGe multiple quantum well QCSE structures on a on a strain-balanced SiGe virtual substrate and formed devices that show modulation at 1310 nm. The wavelength of operation can be changed by tuning the strain in the Ge quantum wells and adjusting the thickness of barrier and well layers, which can be controlled via the epitaxy to one monolayer. By comparing the measured output of devices with the original theoretical design it is possible to model the real system to account for effects such as inter-diffusion between Si and Ge that changes the confinement in the QWs.

Strain can also utilised to advantage in making light emitting devices from Ge. We have fashioned nanostructures on heavily doped Ge that use additional strain to shift the Gamma and L valleys closer and enable direct bandgap transitionsto emit light. This represents significant progress towards silicon based laser structures.

This talk is part of the Condensed Matter Physics Seminars series.

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