Showing papers by "Masao Nishioka published in 2006"

High density InAs∕GaAs quantum dots with enhanced photoluminescence intensity using antimony surfactant-mediated metal organic chemical vapor deposition

Abstract: The antimony surfactant-mediated growth of InAs∕GaAs quantum dots (QDs) by metal organic chemical vapor deposition was investigated. The authors show that the growth of InAs QDs on Sb:GaAs(100) can result in both a strong increase of the dot density, up to 1011cm−2, and the suppression of coalescence. They achieved InAs∕Sb:GaAs QDs with density above 4×1010cm−2, ground-state emission above 1.30μm, and enhanced photoluminescence intensity at room temperature compared to that of InAs∕GaAs QDs. Remarkably, InAs∕Sb:GaAs QDs do not exhibit an emission blueshift under annealing at temperatures as high as 630°C, contrary to InAs∕GaAs QDs.

1.55μm emission from InAs∕GaAs quantum dots grown by metal organic chemical vapor deposition via antimony incorporation

Abstract: The authors report a fabrication technique for redshifting the emission wavelength of InAs quantum dots (QDs) grown on GaAs substrate by metal organic chemical vapor deposition By introducing an antimony irradiation step during the InAs QD growth, the authors have achieved ground-state emission at 155μm (and beyond) from InAs∕GaAs QDs capped by an In024Ga076As strain-reducing layer (SRL) at room temperature (RT) Photoluminescence intensity is strongly enhanced (×100) at RT compared to Sb-free QDs capped by a higher In-content SRL in which ground-state emission saturates at wavelengths shorter than 151μm

Highly efficient optical pumping of photonic crystal nanocavity lasers using cavity resonant excitation

Abstract: The authors demonstrate highly efficient optical pumping of photonic crystal (PhC) nanocavity lasers with InGaAs single quantum wells (QWs) using cavity resonant excitation at 10K. The laser threshold power is largely reduced when the central wavelength of the excitation pulse is resonant with a higher-order cavity mode. The localized excitation by the cavity resonant effect increases the effective absorption of the QW region in the nanocavity. The direct photocarrier generation in the QW also results in the highly efficient optical pumping. This cavity resonant excitation technique can lower the laser threshold of PhC nanocavity lasers and avoid detrimental device heating.

Improved surface morphology of stacked 1.3 mu m InAs/GaAs quantum dot active regions by introducing annealing processes

Abstract: The authors report a simple but effective way to improve the surface morphology of stacked 1.3μm InAs∕GaAs quantum dot (QD) active regions grown by metal-organic chemical vapor deposition (MOCVD), in which GaAs middle spacer and top separate confining heterostructure (SCH) layers are deposited at a low temperature of 560°C to suppress postgrowth annealing effect that can blueshift emission wavelength of QDs. By introducing annealing processes just after depositing the GaAs spacer layers, the authors demonstrate that the surface morphology of the top GaAs SCH layer can be dramatically improved. For a model structure of five-layer QDs, the surface roughness with the introduced annealing processes (IAPs) is reduced to about 1.3nm (5×5μm2 area), much less than 4.2nm without the IAPs. Furthermore, photoluminescence measurements show that inserting the annealing steps does not induce any changes in emission wavelength. This dramatic improvement in surface morphology results from the improved GaAs spacer surface...

Lasing at ~1.3 μm from InAs Quantum Dots with GaInNAs Embedding Layers Grown by Metalorganic Chemical Vapor Deposition

Abstract: Self-assembled InAs quantum dot (QD) lasers emitting at 1.29 mum on GaAs substrates grown by metalorganic chemical vapor deposition (MOCVD) were achieved by using GaInNAs embedding layers. This emission wavelength is the longest wavelength ever reported for QD lasers grown by MOCVD