23 February 2012 The impact of growth rate and barrier thickness on the thermal stability of photoluminescence for coupled InAs/GaAs quantum dot heterostructures with quaternary(InAlGaAs) capping
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Abstract
Multilayer quantum dots were grown using SSMBE. Seed layer of InAs QD was grown over 1000Å intrinsic GaAs layer on semi-insulating GaAs (001) substrate and capped with 30Å quaternary In0.21Al0.21Ga0.58As and 90Å intrinsic GaAs layer for samples A and B while for sample C it was 20Å and 80Å. Growth rate was 0.2011 ML/s for samples A and C whereas 0.094 ML/s for sample B. Each sample was annealed at 650°C, 700°C, 750°C and 800°C. Greater growth-rate produced more strain in samples A and C producing more dot families and for sample B these increased with annealing because of the interdiffusion of constituents among the QDs. 750°C annealed samples A and C showed higher integrated PL intensity and activation energy because carriers found lower minimum energy states for relaxation, attributed to higher growth rate. In/Ga interdiffusion caused blue shift in photoluminescence(PL) spectra for samples B and C at higher annealing temperatures whereas due to greater capping layer thickness almost no shift for sample A due to intermixing of In-Al between the quaternary alloy and wetting layer, making it thermally stable. Decrease in FWHM due to enhanced carrier relaxation is counterbalanced by non-resonant multi-phonon assisted tunneling processes, suggesting good uniformity.
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A. Mandal, U. Verma, S. Chakrabarti, "The impact of growth rate and barrier thickness on the thermal stability of photoluminescence for coupled InAs/GaAs quantum dot heterostructures with quaternary(InAlGaAs) capping", Proc. SPIE 8271, Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling IX, 82710N (23 February 2012); doi: 10.1117/12.907867; https://doi.org/10.1117/12.907867
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