Abstract
An in-depth optimization of growth conditions and investigation of optical properties including discussions on band alignment of GaAsSb/GaAs quantum well (QW) on GaAs by molecular beam epitaxy (MBE) are reported. Optimal MBE growth temperature of GaAsSb QW is found to be 470 ± 10 °C. GaAsSb/GaAs QW with Sb content ~0.36 has a weak type-II band alignment with valence band offset ratio QV ~1.06. A full width at half maximum (FWHM) of ~60 meV in room temperature (RT) photoluminescence (PL) indicates fluctuation in electrostatic potential to be less than 20 meV. Samples grown under optimal conditions do not exhibit any blue shift of peak in RT PL spectra under varying excitation.
Highlights
GaAs1-xSbx/GaAs material system—preferably near 0.36 mole fraction—has been keenly investigated due to its potential for commercial manufacturing of monolithic vertical cavity surface emitting lasers (VCSELs), which operate near 1.3 μm fiber-optic telecommunication spectrum
The devices are based on combination of GaAsSb/GaAs quantum well (QW) and AlGaAs/GaAs distributed Bragg reflectors (DBR)
Similar conclusion can safely be made about fluctuations in electrostatic potential caused by spatial non-uniformity of Sb content in GaAsSb QW because of miscibility gap and Sb segregation driven by lattice mismatch
Summary
GaAs1-xSbx/GaAs material system—preferably near 0.36 mole fraction—has been keenly investigated due to its potential for commercial manufacturing of monolithic vertical cavity surface emitting lasers (VCSELs), which operate near 1.3 μm fiber-optic telecommunication spectrum. There is no clear consensus yet on the type of band alignment in GaAsSb/GaAs system. Blueshift of PL peak is typically attributed to electrostatic band-bending and band-filling of localized states, caused by fluctuations of electrostatic potential in QW, as a consequence of interface roughness or spatial non-uniformity in Sb alloy. There are several reasons for spatial non-uniformity in Sb alloy in GaAsSb layer grown on GaAs. A miscibility gap and Sb segregation caused by built-in mechanical strain are most important among them. An in-depth optimization of growth conditions of GaAsSb on GaAs (1 0 0) by MBE and investigation of optical properties of GaAsSb/GaAs QW, including discussions on possibility of different types of band alignment—through various designs of barrier and cladding layers—are discussed
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