Uk Hyun Lee
Chungnam National University
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Featured researches published by Uk Hyun Lee.
Applied Physics Letters | 1999
Uk Hyun Lee; Dong-Ryul Lee; Heesoon Lee; S. K. Noh; Jae-Young Leem; H. J. Lee
Photoluminescence (PL) from InAs self-assembled quantum dots (QD) embedded in the AlAs matrix was strong and clean around 700 nm. PL efficiency remained quite high at room temperature compared to other QD systems embedded in GaAs cladding layers. Transmission electron microscope pictures from the structure showed a clear formation of relatively small and coherently strained InAs QD. The observed blueshift with accompanying broadening of PL spectra with the increase of excitation power is interpreted in terms of local carrier tunneling in a dense QD system. The PL peak redshift with the increase of temperature was very large, as much as 228 meV. The anomalous shift is interpreted as due to activation-energy differences between dots of different sizes.
Applied Physics Letters | 2001
J. S. Kim; P. W. Yu; Jae-Young Leem; J. I. Lee; S. K. Noh; Jong Su Kim; S. M. Kim; J. S. Son; Uk Hyun Lee; J. S. Yim; Dong-Ryul Lee
Ground-state energy of InAs quantum dots (QDs) in the GaAs matrix can be changed significantly by introducing a thin AlAs layer (1 nm). The photoluminescence (PL) peak position of the QDs grown directly on the thin AlAs layer is blueshifted by 171 meV from that of the QDs grown without the AlAs layer. QDs grown on an additional GaAs thin layer on top of the AlAs layer have PL peaks systematically redshifted to lower energy as the GaAs layer becomes thicker. Time-resolved PL shows that the QDs have similar lifetimes, attesting to the fact that all the QDs grown in this way are of high quality, although the energy level change is large and a thin AlAs layer is introduced.
Journal of Crystal Growth | 2002
Jin-Soo Kim; P. W. Yu; Jae-Young Leem; Joo In Lee; Sam Kyu Noh; Jong Su Kim; Gu Hyun Kim; Se-Kyung Kang; Seung Il Ban; Song Gang Kim; Y. D. Jang; Uk Hyun Lee; Jung Soon Yim; Donghan Lee
We investigated the Si-doped InAs quantum dots (QDs) grown by molecular beam epitaxy and the annealing effects on the QD size distribution through photoluminescence (PL) spectroscopy. A double-peak feature in PL was observed from as-grown InAs QDs with Si-doping, and excitation intensity dependence of PL indicated that the double-peak feature is related to the ground-state emission from InAs QDs with bimodal size distribution. The PL spectrum from Si-doped InAs QDs subjected to annealing treatment at 800°C in nitrogen ambient showed three additional PL peaks and blue-shift of the double-peak feature observed from as-grown sample. The excitation-intensity-dependent PL and consideration of thermal stability of carriers through temperature-dependent PL measurement demonstrated that three additional peaks come from the InAs QDs with three new branches of QD occurring during annealing process.
Physica E-low-dimensional Systems & Nanostructures | 2003
Y. D. Jang; J. S. Yim; Uk Hyun Lee; Donghan Lee; J.W. Jang; Kang Hyun Park; Weon Guk Jeong; Jeun-Woo Lee; D.K. Oh
Abstract A strong and narrow photoluminescence (PL) signal with a full-width at half-maximum of 34 meV emitting at 1.3 μm at room temperature has been obtained from InAsN quantum dots (QD) on GaAs. The PL yield of the 1.3 μm peak at room temperature remains at 8% of the value at 10 K and the carrier lifetime at 10 K is measured to be 600 ps . We believe these values indicate that the grown InAsN QDs are of high crystal quality.
Japanese Journal of Applied Physics | 2003
Uk Hyun Lee; Yong Hoon Kang; Joon Ho Oum; Sang-Jun Lee; Moondok Kim; Sam Kyu Noh; Y. D. Jang; Donghan Lee; Hyung Seok Kim; Chan Hyung Park; Songcheol Hong
We study the influence of doping density and the resulting optimum operation voltage on the performance of quantum dot infrared photodetectors (QDIPs). The optimum operation voltage, where detectivity becomes maximum, becomes smaller as the doping density increases. This is because the optimum dark current levels are similar regardless of the doping density. We confirmed experimentally that the optimum dark current level is ~5 mA (current density: ~A/cm2) for our samples. It is found that the higher doping density improves the performance in the range used in this experiment (5×1016–5×1017/cm3). The response to a normal incident light is confirmed and the possibility of high-temperature operation of QDIP is shown.
The Japan Society of Applied Physics | 2004
Joon Ho Oum; Uk Hyun Lee; Yong Hoon Kang; Jong Ryul Yang; Songcheol Hong
This work was supported, in part, by KISTEP (under Nano-Structure Technology Projects and IMT2000 R&D donation support program) and the MOE BK21 program
Journal of Electronic Materials | 2000
Sukho Yoon; Youngboo Moon; Tae-Wan Lee; Heedon Hwang; Euijoon Yoon; Young Dong Kim; Uk Hyun Lee; Donghan Lee; Hong-Seung Kim; Jeong Yong Lee
Journal of the Korean Physical Society | 2003
Y. D. Jang; Uk Hyun Lee; H. Lee; Dooyong Lee; Jong Su Kim; Jae-Young Leem; Seunguk Noh
Journal of the Korean Physical Society | 2003
Se-Kyung Kang; S. J. Lee; Jungil Lee; Moon-Deock Kim; Seunguk Noh; Yong Hoon Kang; Uk Hyun Lee; Songcheol Hong; Hyun-Taek Kim; Chan Gyung Park
Journal of the Korean Physical Society | 2000
Uk Hyun Lee; J. S. Yim; D. Lee; H. G. Lee; Seunguk Noh; Jae-Young Leem; Hwack Joo Lee