Ryoichiro Suzuki

Photoluminescence Characteristics of InAs Quantum Dots with GaInP Cover Layer Grown by Metalorganic Chemical Vapor Deposition

The photoluminescence (PL) characteristics of InAs quantum dots (QDs) with a GaInP cover layer grown by metalorganic chemical vapor deposition were investigated to clarify the effect of the cover layer. By comparing the PL peak wavelength between the GaInP and GaInAs covered structures, the strain of the cover layer was identified as the main mechanism responsible for the emission wavelength shift of the InAs QDs. The PL emission efficiency and the thermal annealing effect of the GaInP-covered structure were also investigated.

Reduction of spacer layer thickness of InAs quantum dots using GaNAs strain compensation layer

Emission and shape characteristics of the InGaAs covered InAs quantum dots with GaNAs strain compensation layers (SCLs) are investigated, focusing on the reduction of the spacer thickness for device applications. Using the GaNAs SCL, the suppression of inhomogeneous emission broadening induced by the compressive strain from lower dot layers was confirmed with the suppression of increase in the dot size of upper dot layers. This result is effective for the suppression of the spacer thickness.

Photoluminescence Characterization of InAs Quantum Dots on GaNAs Buffer Layer by Metalorganic Chemical Vapor Deposition

The photoluminescence (PL) characteristics of InAs quantum dots on a GaNAs buffer layer grown by metalorganic chemical vapor deposition were investigated. A maximum 60 nm redshift was observed for a nitrogen composition of less than 3% in the buffer layer with an increase in emission efficiency in comparison with a conventional GaAs buffer layer. A large intensity increase with a blueshift of PL was observed for a buffer layer of 3% nitrogen composition. These were due to a change in the dot morphology on the GaNAs buffer layer. The InAs supply and growth temperature dependences of PL properties were also examined in detail.

InAs Quantum Dot Growth on a Thin GaNP Buffer Layer on GaP by Metalorganic Chemical Vapor Deposition

InAs quantum dots (QDs) on a 2-nm-thick GaNP buffer layer on GaP were investigated using low-pressure metalorganic chemical vapor deposition. The InAs QDs density was significantly increased from 2.6×109 to 2.0×1010 cm-2 by increasing the nitrogen composition from 0 to 4.5% in GaNP. The formation characteristics of InAs QDs were also investigated at various InAs supply amounts from 0.7 to 2.5 monolayers (ML). The generation of QDs on the GaNP and GaP buffer layers started at the InAs supplies of 1.0 and 1.1 ML, respectively. Since the lattice mismatches were large, these supply amounts were definitely smaller than that on GaAs.

Post-thermal Annealing Effects on Photoluminescence Properties of InAs Quantum Dots on GaNAs Buffer Layer

The thermal annealing characteristics of InAs quantum dots (QDs) on a GaNAs buffer layer grown by the metalorganic chemical vapor deposition were investigated. Although the photoluminescence efficiency was deteriorated by annealing, the improved tolerance in the annealing time and temperature was confirmed in comparison with the GaAs buffer sample. The wavelength blue shift was similar in both buffer layers. The improvements in the PL efficiency were considered to be related to the decreased coalescent QDs upon introducing the dilute-nitrogen into the buffer layer.

Multilayer InAs Quantum Dot with GaNAs Strain Compensation Layers Partly Inserted in a Thin Spacer Layer

Multilayer InAs quantum dot with a thin spacer prepared using a GaNAs strain compensation layer was investigated by metalorganic chemical vapor deposition. The GaNAs tensile strained layer was inserted partly in the spacer without contacting with the compressively strained InAs dot and GaInAs cover layer. The stacking number of up to 5 with a thin spacer of 18 nm was realized at a wavelength of 1.4 µm without severe degradation of optical quality although a slight dot size increase in the upper layer was confirmed. The result indicates the advantageousness of GaNAs for a thin spacer structure of the multilayer quantum dot.

Reduction of surface roughness of GaP on Si substrate using strained GaInP interlayer by MOCVD

Epitaxial growth of GaP on a Si substrate with a GaInP interlayer by a low-pressure metalorganic chemical vapor deposition were investigated using the atomic force microscopy. The surface roughness Ra was decreased from 2.7 nm to 1.3 nm by only inserting the GaInP interlayer under the 600°C. The GaP layer using the GaInP interlayer was optimized under various growth temperature between 500°C and 650°C. The surface roughness Ra was drastically decreased to 0.5 nm when both the GaP and the GaInP interlayer was grown at 550°C.

Photoluminescence characteristics of MOCVD grown-InAs quantum dots covered by GaInP layer

PL characteristics of MOCVD-grown InAs QDs using a GaInP cover layer were investigated. It is confirmed that the strain modification effect of the cover layer regardless of growth methods is a cause of wavelength shift of QDs.

InAs QDs on thin GaP 1−x N x buffer on GaP by MOCVD

GaP-based InAs quantum dots (QDs) on a thin GaP<inf>1−x</inf>N<inf>x</inf> buffer layer grown by the low-pressure metalorganic chemical vapor deposition were investigated by the atomic force microscopy. The InAs dot density was significantly increased from 2.6×10⁹ cm⁻² to 2.0×10¹⁰ cm⁻² with increasing the nitrogen composition of the GaP<inf>1−x</inf>N<inf>x</inf> from x = 0 to 4.5. The InAs QDs grown on GaP and GaPN with various InAs supply from 0.7 monolayer (ML) to 2.5 ML was also investigated. The dot density of the InAs QDs on GaPN and GaP buffer layers drastically increased at the InAs supply of 1.0 ML and 1.1 ML, respectively. The InAs dot density was saturated when the InAs supply was more than 1.4 ML.

Self-assembled GaInNAs quantum dot by MOCVD

MOCVD grown self-assembled quantum dot using dilute nitrogen material system (GaInNAs) is presented for GaAs-based long wavelength VCSELs. Suppression of Coalescence and inhomogeneous broadening by incorporating nitrogen into dot structure is particularly discussed.