Self-assembled GaSb/GaAs quantum dots and rings for light-emitting devices

Vertical-cavity surface-emitting-lasers (VCSELs) are cheap, fast and readily coupled to optical fibres, so ideal light sources for the datacoms and telecoms markets. However, commercial telecoms VCSELs are not available: conventional VCSELs are based on GaAs and it has proven difficult to get them emit beyond 1000 nm, placing the crucial 1260 to 1675 nm telecoms range out of reach for this technology. Furthermore, there is a market drive pushing the operational wavelength of datacoms from ~900 nm, where VCSELs are available, into the telecoms band, where they are not. High operating temperature (85C) is another key market demand. GaSb quantum dot/ring devices can fulfil both needs: a direct result of the unique deep hole-confining potential. An additional application, for which the technology is very similar, is cheap, electrically-driven, room-temperature, telecoms-wavelength, single-photon sources for quantum key distribution. The project will concentrate on improving GaSb quantum ring devices by (i) increasing radiative recombination rate, (ii) reducing carrier loss from non-radiative recombination, (iii) pushing emission further into the telecoms band.