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Optical Properties of InGaN/GaN Multiple Quantum Wells
JooInLee,ChangMyungLee,Jae-YoungLeem,Ki-SooLim,한일기 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.3
We have used steady-state and time-resolved photoluminescence to investigate optical properties of In0:13Ga0:87N/GaN multiple quantum wells (MQW) grown by using metalorganic chemical vapor deposition. The quantum well spectra were explained in terms of the radiative recombination of excitons in the localized states. Exciton formation of the InGaN MQW might be delayed for excitations above the GaN barrier excitation compared with exciton formation in excitations below the GaN barrier. The critical temperature at which nonradiative recombination dominantly occurred was increased under the excitation below the GaN barrier because screening caused by carriers in the GaN barrier vanished.
Post-Growth Annealing Effects of In0.5Ga0.5As Quantum Dots Grown by Heterogeneous Droplet Epitaxy
ChangMyungLee,JooInLee,Jae-YoungLeem,Dong-HanLee,TakaakiMano,T.Tateno,NobuyukiKoguchi 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.1
Post-growth rapid thermal annealing modifies the structural and the optical properties of the In$_{0.5}$Ga$_{0.5}$As quantum dots grown on GaAs substrates by using heterogeneous droplet epitaxy. It is found that at annealing temperatures up to 750 $^\circ$C, a significant decrease in the intersublevel ($E_{01}=E_{1} - E_{0}$) from 55 to 23.7 meV occurs together with about a 62-meV blueshift. Also, we observe a decrease in the activation energy of about 200 meV. These results are explained by interdiffusion of In-Ga atoms at the interface between the QD and the GaAs barrier, which changes the composition of the QDs.
Joo in Lee,Jae-Young Leem,J. S. Son,A. Kasi Viswanath 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.3
We have studied the photoluminescence properties of undoped epitaxial layers of GaN on sapphire substrate grown by horizontal low pressure metal organic chemical vapor deposition method in the temperature range of 9-300 K. At 9 K the spectra are dominated by the well resolved interband free excitons A and B as well as bound excitons. Temperature dependence of free exciton transitions was studied and Varshni′s coefficients for the temperature variation of bandgap were determined.
Phonon bottleneck effects of InAs quantum dots
Joo In Lee,Sungkyu Yu,Jae Young Leem,Hyung Gyoo Lee 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.1
We have studied the carrier relaxation of InAs/GaAs modulation-doped quantum dots depending on the excitation wavelength and modulation-doping concentration by using the time-ressolved spectroscopy. At the excitation below GaAs barrier band gap, the relaxation processes become very slow, implying to observe the phonon bottleneck effects. On the other hand, at the excitation far above GaAs band gap, phonon bottleneck effects are broken down due to Auger processes. Increasing modulation-doping concentration, the relaxation times, by virtue of Coulomb scattering between electrons in GaAs doped layer and carriers in InAs quantum dots, are observed to become fast.
Exciton Dynamics of GaAs / AlGaAs Quantum Wells
Joo In Lee,Jae-Young Leem,Sungkyu Yu,Chang Myung Lee 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.2
We present a study of exciton relaxation in GaAs/AlGaAs quantum well structures by using time-resolved photoluminescence techniques. We observed that light-hole exciton has a longer decay time than heavy-hole exciton, which results from the difference of the exciton population factor. We considered the thermal population time to explain the observed exciton dynamics.
Time - resolved photoluminescence spectroscopy of InGaN multiple quantum wells
Joo In Lee,Eun-joo Shin,J. Y. Leem,S. T. Kim,G. S. Lim,H. G. Lee 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.1
We have fabricated by metal organic chemical vapor deposition (MOCVD) In_(0.13)Ga_(0.87)N/GaN multiple quantum well (MQW) with thickness as thin as 10 Å and barriers also of th same width on (0001) sapphire substrate. We have investigated this thin MQW by steady-state and time-resolved photoluminescence (PL) in picosecond time scale in a wide temperature range from 10 to 290 K. In the PL at 10 K, we observed a broad peak at 3.134 eV which was attributed to the quantum well emission of InGaN. The full width at half maximum (FWHM) of this peak was 129 meV at 10 K and its broadening at low temperatures was considered to be due to compositional fluctuations and interfacial disorder in the alloy. The narrow width of the quantum well was mainly responsible for the broadening of the emission linewidth. We also observed an intense and sharp peak at 3.471 eV of GaN barrier. From the temperature dependent PL measurements, the activation energy of the InGaN quantum well emision peak was estimated to be 69 meV. The lifetime of the quantum well emission was found to be 720 ㎰ at 10 K, which was explained in terms of the exciton localization arising from potential fluctuations.