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Shi Jong Leem,Young Chul Shin,Eun Hong Kim,Chul Min Kim,이병규,이완호,Youngboo Moon,김태근 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
We report the effect of the barrier growth temperature of InGaN/GaN multi-quantum wells on the breakdown voltage of light emitting diodes. We adopted a two-step varied-barrier-growth temperature method to improve the structural and the electrical properties of the InGaN/GaN MQW layers. The depth of the V defect of InGaN/GaN MQW surfaces was decreased up to 20 °A by using a GaN barrier layer grown at a high growth temperature of 1000 C as compared to the conventional sample without varying the GaN barrier growth temperature. we found that the breakdown voltage increased to as high as about –25 V at a 10 μA reverse current.
Optical Properties of Europium-Silicate Thin Films Fabricated on Different SiOx Intermediate Layer
Young Chul Shin,김태근,Cheol Koo Hahn,Eun Hong Kim,Shi Jong Leem 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.6
We report the effect of SiO$_x$ intermediate layers on the photoluminescence properties of europium-silicate thin films. Layer structures of Eu$_2$O$_3$/SiO$_x$/Si (100) were deposited by using an rf-sputtering method and were annealed at 1100 $^{\circ}\mathrm{C}$ by rapid thermal annealing (RTA). Two methods were used for the deposition of the SiO$_x$ layer: sputtering using a SiO$_2$ target (Ar gas at a rate of 50 sccm) and reactive sputtering using a Si target (Ar gas at a rate of 45 sccm with O$_2$ gas at a rate of 5 sccm). The photoluminescence peak at 430 nm was observed in the sample with a SiO$_x$ interlayer sputtered from a SiO$_2$ target. In comparison, a PL peak at 570 nm was observed in the sample where SiO$_x$ layer had been deposited by reactive sputtering from a Si target.
Dong Ho Kim,김태근,Cheol-Koo Hahn,Cheong Hyun Roh,Hong Joo Song,Hoon Kim,Shi Jong Leem 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
We report on the electrical characteristics of the InAs self-assembled quantum dots (SA-QDs) resonant-cavity separate absorption, charge, and multiplication avalanche photodetector (RC-SACM APD) improved by optimizing the layer parameters, such as the anti-node position of an incident optical standing wave of the InAs QDs as an light-absorbing layer, the doping concentration of the Al$_{0.2}$Ga$_{0.8}$As charge layer (N$_{a}$ = 1 $\times$ 10$^{18}$/cm$^{3}$), and the layer thickness calibrated by using Bragg's quarter-wavelength rule. The optimized InAs QDs RC-SACM APD exhibited very low dark current of 163 pA, a high photocurrent of 66 nA, and a very low breakdown voltage of --12.3 V. In addition, the avalanche multiplication gain was remarkably increased up to 1648.
Characteristics of Nitride-Based Laser Diode Grown on SiO2-Removed Laterally Overgrown GaN
윤호 최,Hee-Suk Song,Hwan Kuk Yuh,Jae Hyung Yi,Jina Jeon,Junghoon Lee,Min Hong Kim,Shi-Jong Leem,Sungwon Khym 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Systematic study on SiO$_2$-removed laterally epitaxially overgrown (SR-LEO) GaN layers was carried out to determine the effects of SiO$_2$ removal and thermal annealing. After the first phase of SR-LEO preparation when the growth is stopped just before coalescence of adjacent wings, X-ray diffraction (XRD) measurements showed broad split peaks with tilting angle of about 0.5$^\circ$. After the oxide masks were etched away the broad peaks were replaced by sharp peaks with tilting angle of only about 0.2$^\circ$, suggesting elastic deformation originating from the interface between overgrown GaN and SiO$_2$ mask to be a major source of crystallographic tilting in conventional LEO layers. The low-angle tilt is attributed to plastic deformation from in-plane defects that arise during the initial lateral growth phase and residual elastic deformation within the wing region. In order to assess the practicality of this novel LEO technique for device applications, a SR-LEO GaN was used as a base layer to fabricate index guided laser diodes with cavity length of 500 $\mu$m and ridge width of 2.3 $\mu$m. Under continuous wave operation at room temperature, the threshold current was 68 mA, which corresponded to a threshold current density of 5.9 kA/cm$^2$, and the operating voltage at threshold was 5.3 V.
High-Power 0.81 m Tensile Strained GaAsP/InGaP Diode Lasers
철회 김,Eun-Ah Lee,Ki-Young Um,Kyoung-Hee Moon,Sang-Hyun Lee,Shi-Jong Leem,Sung-Min Hwang 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
In this paper, we present high-power Al-free active laser diodes of 0.81 $\mu$m wavelength. For high power and narrow beam divergence, threshold current density, efficiency and transverse beamwidth are calculated. The epilayers are grown by low-pressure metalorganic chemical vapor deposition. The active region consists of a tensile strained GaAsP quantum well and InGaP barriers. We have obtained a maximum optical power of 3.2 W and an internal optical power density of 12.2 MW/cm$^{2}$ with cavity length of 1mm, ridge width of 50 $\mu$m, waveguide thickness of 0.6 $\mu$m and 9 mm TO-CAN type package. The characteristic temperature for threshold current density is 148.6 K in the range of 10-60 $^\circ$C. Also, it is expected that Al-free GaAsP/InGaP quantum well laser diodes will have good reliability without a facet treatment.
Optimization of 660-nm-Band AlGaInP Laser Diodes by Using Deep-Level Transient Spectroscopy Analyses
Young Chul Shin,김태근,Bum Jun Kim,Byoungjin Ma,Chang Yun Lee,Dong Hoon Kang,Joon Seok Kang,김문덕,Sang Bum Lee,Shi Jong Leem,조수행,Yongjo Park,Young Min Kim 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
We report high power and high temperature operation of 660-nm-band AlGaInP laser diodes. The double-channel ridge waveguide structure was used, and the growth conditions for each layer of the AlGaInP laser were optimized to have the lowest defect density by using deep-level transient spectroscopy (DLTS) analyses. The optimized AlGaInP lasers showed better performance than those fabricated without optimization. One of the optimized AlGaInP lasers showed a very stable fundamental transverse mode even at 200 mW and 70 $^{\circ}\mathrm{C}$, a typical threshold current of 64 mA at 660 nm, a slope efficiency of 1.0 W/A, and a characteristic temperature of 212 K. The beam divergences perpendicular and parallel to the junction plane were 15.3$^{\circ}$ and 8.6$^{\circ}$, respectively, at 80 mW CW, which is small enough for a DVD-R/RW system.