약속어음의 발행인과 배서인이 소지인에 대하여 지는 합동책임

박승환 한국상사판례학회 1989 상사판례연구 Vol.3 No.1

Modulation Doping Effect in the Optical Gain of Type-II GaAsSb/GaAs Quantum-Well Structures

박승환 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4

The effect of modulation doping on the optical gain characteristics of type-II GaAsSb/GaAs quantum-well (QW) lasers was investigated using a self-consistent method. The interband transition energy gradually increased with n-type modulation doping. However, in the case of p-type modulation doping, the rate of increase was found to be smaller than that of n-type modulation doping. The optical gain was found to be largely enhanced by an increasing n-type modulation doping density. This could be explained by the fact that the optical matrix element was greatly increased due to the band-bending effect. On the other hand, in the case of p-type modulation doping, the optical gain was slightly smaller than that for n-type modulation doping because the optical matrix element was reduced by the negative charge from the ionized acceptors near the well. The effect of modulation doping on the optical gain characteristics of type-II GaAsSb/GaAs quantum-well (QW) lasers was investigated using a self-consistent method. The interband transition energy gradually increased with n-type modulation doping. However, in the case of p-type modulation doping, the rate of increase was found to be smaller than that of n-type modulation doping. The optical gain was found to be largely enhanced by an increasing n-type modulation doping density. This could be explained by the fact that the optical matrix element was greatly increased due to the band-bending effect. On the other hand, in the case of p-type modulation doping, the optical gain was slightly smaller than that for n-type modulation doping because the optical matrix element was reduced by the negative charge from the ionized acceptors near the well.

Electrical and Optical Properties of Al-Doped ITO Thin Films

박승환,김용기,Sung-Won Ryu,김덕수,이병로,김종재,홍우표,김화민 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

The electrical and the optical properties of Al-doped ITO films deposited by using an rf-magnetron sputtering method on Corning glass and plastic (PET and PEN) substrates are investigated. Films deposited on Corning glass show a resistivity that continuously dereases with reducing distance dst between the substrate and the target due to the improved mobility. On the other hand, in the case of the lms deposited on plastic substrates, the resistivity increases with decreasing dst in a range of small dst. The optical bandgap of the films deposited on plastic substrates is observed to be smaller than that of the films deposited on Corning glass. Films deposited on Corning glass change from microcrystalline to amorphous with increasing distance. On the other hand, in films deposited on the plastic substrate, the XRD peak in the (400) plane is observed even at a large distance between the substrate and the target. The transmittance of the film deposited on a PEN substrate is found to be comparable to that of the film deposited on Corning glass.

Many-Body Optical Gain in Zinc-Blende GaN/AlGaN Quantum Wells with (001), (111) and (110) Crystal Orientations

박승환 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3

Many-body optical gain in (001)-, (111)- and (110)-oriented zinc-blende GaN/AlGaN quantum-wells (QWs) was investigated by using a non-Markovian optical gain model with many-body effects. The transition energy of the (110)-oriented QW structure was shown to be larger than that of the (001)- or the (111)-oriented QW. For a given carrier density, the (111)-oriented QW structure has a smaller optical gain and a larger transparency carrier density than the (001)- or the (110)-oriented QW structure. This can be explained by the fact that the (111)-oriented QW has a smaller matrix element and a larger heavy-hole effective mass than the (001)- or the (110)-oriented QW structure. In addition, the (111)-oriented QW structure showed a larger transparency carrier density compared to the (001)- or the (110)-oriented QW. The increase in the transparency carrier density observed in the (111)-oriented QW is attributed to the fact that the quasi-Fermi level separation is reduced due to the larger hole effective mass. Many-body optical gain in (001)-, (111)- and (110)-oriented zinc-blende GaN/AlGaN quantum-wells (QWs) was investigated by using a non-Markovian optical gain model with many-body effects. The transition energy of the (110)-oriented QW structure was shown to be larger than that of the (001)- or the (111)-oriented QW. For a given carrier density, the (111)-oriented QW structure has a smaller optical gain and a larger transparency carrier density than the (001)- or the (110)-oriented QW structure. This can be explained by the fact that the (111)-oriented QW has a smaller matrix element and a larger heavy-hole effective mass than the (001)- or the (110)-oriented QW structure. In addition, the (111)-oriented QW structure showed a larger transparency carrier density compared to the (001)- or the (110)-oriented QW. The increase in the transparency carrier density observed in the (111)-oriented QW is attributed to the fact that the quasi-Fermi level separation is reduced due to the larger hole effective mass.

Effect of Modulation Doping on the Spontaneous Emission Characteristics of Wurtzite GaN/AlGaN Quantum Well Structures

박승환 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

The effect of modulation doping on the spontaneous emission characteristics of wurtzite GaN/AlGaN QW structureswas investigated. The overall potential profile is nearly not affected by the modulation doping, except for the fact that the potential well bottom in the conduction band becomes deeper while that in the valence band becomes shallower. The interband transition wavelength gradually decreases with increasing injection carrier density due to an increase in the screening electric field. In the range of relatively low carrier densities, the spontaneous emission coefficient is observed to be greatly enhanced with increasing doping density. This can be explained mainly by the fact that the quasi-Fermi level separation is increased by modulation doping because the optical matrix element is nearly not affected by doping. Also, the spontaneous emission coefficient is shown to be nearly saturated at a higher modulation doping density (Nδ = 7 × 1012 cm−2).

Barrier Effects on Exciton Binding Energies in Zinc-blende CdZnSe/ZnSSe Quantum Well Structures

박승환,김종재,김화민 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.1

Barrier effects on the exciton binding energies of CdZnSe/ZnSSe quantum well (QW) structures were investigated within the framework of effective mass theory. The exciton binding energy gradually increases with increasing S composition in the barrier for the QW structure with a relatively thin well width (Lw = 10 Å). On the other hand, in the case of the QW structure with a relatively thick well width (Lw = 30 Å), the exciton binding energy is found to be a weak function of the S composition in the barrier. Also, the QW structure with a thin well width (Lw = 10 Å) has a larger exciton binding energy than that with a thick well width (Lw = 30 Å). This can be explained by the fact that the three-dimensional character of the exciton is restored due to the increase of the spatial extent of the electron and the hole wavefunctions for the QW structure with the thick well width.

1.3 및 1.55㎛ GaAsSb/InGaNAs/GaAs Trilayer 양자우물 구조의 광학적이득 특성

박승환 한국물리학회 2010 새물리 Vol.60 No.10

The optical gain characteristics of 1.3 ㎛ GaAsSb/InGaNAs/GaAs trilayer quantum well structures were studied using multi-band effective mass theory. The results were compared with those of 1.55㎛ GaAsSb/InGaNAs/GaAs trilayer quantum well structures. The transition wavelength gradually decreases with increasing carrier density due to the band-bending effect. In the case of the 1.3㎛ GaAsSb/InGaNAs/GaAs trilayer quantumwell structure, the rate of decrease is shown to be smaller than that of the 1.55㎛GaAsSb/InGaNAs/GaAs trilayer quantum well structure due to a reduced band-bending effect. Also, the 1.3 ㎛ quantumwell structure shows a larger optical gain than the 1.55 ㎛ quantumwell structure because the former has a larger optical matrix element than the latter. On the other hand, the quasi-Fermi level of the 1.3㎛ quantum well structure is slightly smaller than that of the 1.55 ㎛ quantumwell structure. 본 연구에서는 1.3 ㎛ 와 1.55 ㎛ 파장을 가진 type-Ⅱ GaAsSb /InGaNAs / GaAs trilayer 양자우물 레이저에 대한 광학적특성을 조사하고이것을 서로 비교 연구하였다. 천이 파장은 운반자 밀도가 증가함에 따라band-bending 효과에 의해 감소하였으며, 특히 1.55 ㎛ 의 양자우물구조의 경우 1.3 ㎛ 의 양자우물 구조에 비해 감소 효과가 더 크게나타났다. 1.3 ㎛ 의 양자우물 구조가 1.55 ㎛ 의 양자우물 구조보다 더 큰 광학적 이득 값을 보여주었는데, 이것은 주로 광학적매트릭스 요소가 크기 때문인 것으로 나타났다. 반면, 준페르미 준위는포텐셜 우물의 깊이가 더 깊은 1.55 ㎛ 의 양자우물 구조의 경우가더 크게 나타났다.

Optical Properties of Green InGaN/GaN Quantum-Wel Light-Emitting Diodes with Embedded AlGaN Layer

박승환,Yong-Tak Lee,Jongwoon Park 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1

The optical characteristics of green InGaN/GaN double-quantum-well (QW) structures with embedded AlGaN layers are investigated using the multiband effective mass theory. These results are compared with those of single QW structure without a layer. A double QW structure has a much larger spontaneous emission than a single QW structure for a relatively thick well width (Lw= 5 nm) because a double QW structure has a larger optical matrix element and a smaller effecive well width than a single QW structure. The inclusion effect of a layer is found to be dominant at a relatively thick well width. However, the double QW structure is shown to need a slightly larger In composition to obtain the same transition wavelength as the single QW structure.

Light Emission Characteristics of Blue Strain-compensated InGaN/InGaN/InGaN Light-Emitting Diodes

박승환 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.2

The light emission characteristics of blue strain-compensated InGaN/InGaN light emitting diodes(LEDs) grown on InGaN substrates were investigated using the multiband effective mass theory. The radiative recombination rate of the strain-compensated LED structure is shown to be largerthan that of the conventional LED structure due to the decrease in the lattice mismatch with thesubstrate. Also, the light emission distribution in quantum wells (QWs) for the strain-compensatedLED structure is found to be much more uniform than that for the conventional LED structure. As a result, the simulation results suggest that the efficiency droop is significantly improved whena conventional GaN barrier and substrate are replaced by an InGaN barrier and substrate. Thus,a possibility exists to employ a strain-compensated QW to improve the optical performance ofInGaN-based blue LEDs.

Theoretical Study of a Two-dimensional Electron Gas in Wurtzite ZnO/MgZnO Heterostructures and Comparison with Experiment

박승환,홍우표,김종재,안도열 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.10

The effect of polarization on a two-dimensional electron gas in the ZnO/MgZnO heterostructure were investigated by using an effective mass theory. The O-face MgZnO/ZnO structure is shown to have a larger sheet carrier density than the Zn-face structure. This can be explained by the fact that, in the case of the O-face, the ZnO layer is under tensile strain, and the strain-induced polarization is parallel to the orientation of the spontaneous polarization. The calculated results for the O-face agree well with the experiment. Also, the contribution of additional donor impurities on the electron sheet concentration is shown to be less effective when the Mg mole fraction is large.