Capping of InAs/GaAs Quantum Dots for GaAs Based Lasers
Nowadays, self-assembled InAs quantum dots grown on GaAs substrates are intensively studied due to their potential applications: quantum dot ensembles are employed in laser active regions and mid-infrared detectors, single quantum dots have a potential for application in memories, two-level information processing or single photon sources (Henini& Bugajski, 2005; Mowbray& Skolnick, 2005; Battacharya, 2007).
Emission dynamics of InAs self-assembled quantum dots with different cap layer structures
The emission dynamics properties of self-assembled InAs quantum dots with different cap layers are investigated by steady-state and time-resolved photoluminescence (PL). The uniformity of the dots can be improved by the proper cap layer structure. It is found that the InGaAs and InAlAs combination cap layer structure could more effectively release the strain in QDs, suppress the indium segregation, enhance the confinement effect on carriers and reduce the thermally induced carrier escape from QDs. This has led to QDs with narrower emission, above 1.3 µm, and to improved temperature stability of PL intensity and has resulted in an increase of the PL decay time to 10 ns at 160 K.
Characterization of self-assembled InAs quantum dots with InAlAs∕InGaAs strain-reduced layers by photoluminescence spectroscopy
The optoelectronic characteristics of self-assembled InAs quantum dots (QDs) with strain-reduced layers (SRLs) were investigated using photoluminescence (PL) spectroscopy. Various SRLs that combine In0.14Al0.86As and In0.14Ga0.86As with the same total thickness were examined to ascertain their confining effect on carriers in InAs QDs. The emission wavelength is blueshifted as the thickness of InAlAs is increased. The energy separation between the ground state and the first excited state of QDs with InAlAs SRLs greatly exceeds that of QDs with InGaAs SRLs. Atomic force microscopic images and PL spectra of the QD samples demonstrated that high-quality InAs QDs with long emission wavelengths and a large energy separation can be generated by growing a low-temperature, thin InAlAs SRL onto self-assembled QDs.