Kwangmin Park

Effects of thin GaAs insertion layer on InAs∕(InGaAs)∕InP(001) quantum dots grown by metalorganic chemical vapor deposition

We studied the influence of a thin GaAs insertion layer (5–10 monolayers) on the optical properties of InAs QDs grown by metalorganic chemical vapor deposition. The insertion of a 10 monolayer (ML) thick GaAs layer on the InAs QDs led to significant photoluminescence blueshifts of 54 and 111meV when they were grown on InGaAs and InP, respectively. In addition, a narrowing of full width at half maximum was observed when the thicker GaAs insertion layers and higher overgrowth temperature for the top capping layer were used. These results can be applied for tuning the emission wavelength around 1.55μm for optical fiber communication.

Anomalous strain profiles and electronic structures of a GaAs-capped InAs/In0.53Ga0.47As quantum ring

We investigate the strain profiles and electronic structures of a novel quantum ring capped by a material different from the substrate. By comparing the novel quantum ring with an ordinary quantum dot and quantum ring, which are capped by the same material as the substrate, we find that the novel quantum ring exhibits noticeably different properties, such as an anomalous strain relaxation, band alignments, and blueshift of the emission energy. We investigate the novel properties of our quantum ring by separating the ring evolution process into (i) the step of geometric change from a dot to ring and (ii) the step of GaAs capping. The GaAs embedded in the In0.53Ga0.47As matrix provides sufficient space for the relaxation of InAs and, thus, individual strain and biaxial strain of the InAs ring are considerably reduced by the GaAs layer. We show that the blueshift in the emission energies due to ring formation is mainly caused by (i) the geometric change from a dot to ring and (ii) the weakened heavy hole–lig...

Growth and in situ analysis of InAs/InP quantum dot stack and its far infrared absorption properties

InAs/InP self-assembled quantum dots (SAQDs) are promising active layers for optical devices for fiber-optic communication. Furthermore, they may be used for the fabrication of uncooled mid and far infrared detectors. InAs/InP SAQDs were grown by low pressure-metalorganic chemical vapor deposition, where As/P exchange reaction and growth interruption step play an important role. The InAs quantum dot (QD) stacks were successfully grown on (001) InP substrate and their optical properties were characterized. Far-infrared absorption peaks were observed at 819 cm-1 (12.20 μm) and 518 cm-1 (19.35 μm) at room temperature by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Raman analysis showed that the peak at 819 cm-1 was attributed to a plasmon related peak in the n-type InP substrate. On the other hand, the absorption peak at 518 cm-1 was regarded as a peak related with intersubband transition in the InAs QDs, suggesting that room temperature operating quantum dot infrared photodetectors (QDIPs) can be fabricated. In situ monitoring of the QD evolution and stacking sequences were also discussed.

Effects of thin GaAs cap layer on optical properties of InAs/InGaAs/InP quantum dot

We have studied the influence of thin GaAs capping layer (5-10 monolayers) on optical properties of InAs QDs. After the growth of thin GaAs capping layer, the 70 nm thick top InGaAs capping layer was deposited at 570 /sup o/C or 610 /sup o/C. The insertion of thin GaAs cap layer on QDs led to blue shift of peak of photoluminescence (PL). In addition, full width at half maximum (FWHM) of the PL peak decreases from 35 mev to 20 mev by inserting 10 ML GaAs layer.