Jong-Jae Kim

Heat treatment effects on electrical and optical properties of ternary compound In2O3–ZnO films

Heat treatment effects on the electrical and optical properties are investigated for In2O3–ZnO film with a Zn content [Zn/(In+Zn)] of 33 at. %. Thin films deposited in a mixed gas atmosphere (Ar+20% O2) by a magnetron sputtering method show high resistivity of about 1.7×10−1 Ω cm. A mixture of In2O3 (99.999%) and ZnO (99.999%) powders calcined at 1000 °C in an Ar atmosphere for 2 h was used as the target. On the other hand, the films deposited in a pure Ar gas environment show low resistivity of about 3×10−4 Ω cm, comparable to that of indium tin oxide films (10−4 Ω cm). After heat treatment at 650 °C in vacuum, it was found that the films deposited in a mixed gas atmosphere revealed low resistivity similar to that of films deposited in a pure Ar gas. For these annealed films, their electrical properties are very stable when treated at temperatures up to 500 °C in air or 650 °C in vacuum. Also, it is found that the optical band gap of In2O3–ZnO films increase (or decrease) after the heat treatment in vacu...

New Solitary-Wave Solutions for the Generalized Reaction Duffing Model and their Dynamics

We find new analytic solitary-wave solutions, having a nonzero background at infinity, of the generalized reaction Duffing model using the auxiliary function method. We study the dynamical properties of the solitary-waves by numerical simulations. It is shown that the solitary-waves can be stable or unstable depending on the coefficients of the model. We study the interaction dynamics by using the solitary-waves as initial profiles to show that the nonlinear terms may act as an effective driving force. - PACS numbers: 03.40.Kf, 02.30.Jr, 47.20.Ky, 52.35.Mw

Characteristics of built-in polarization potentials in vertically and laterally arranged InGaN/GaN quantum dots

Built-in polarization potentials for vertically and laterally arranged InGaN/GaN quantum dot (QD) structures are investigated using the finite-element method based on the theory of continuum elasticity. The potential for vertically arranged QD structures is shown to depend significantly on the number of arranged QD. On the other hand, in the case of laterally arranged QD structures, the potential is shown to be nearly independent of the number of arranged QD. In the case of three vertically arranged QDs, the potential in the central QD is greatly reduced. Similar result is observed in structures with more QDs than three. On the other hand, the reduction effect is not observed in the case of two QDs. The electric field in the central QD region for three vertically arranged QDs is nearly constant and is shown to be smaller compared to that in the left or right QD region. We observe that the potential in the central QD increases with increasing spacer layer thickness.

Properties of ZrO 2 Gas Barrier Film using Facing Target Sputtering System with Low Temperature Deposition Process for Flexible Displays

film was deposited by facing target sputtering (FTS) system on polyethylene naphthalate (PEN) substrate as a gas barrier layer for flexible organic light emitting devices (FOLEDs), In order to control the heat of the FTS system caused by the ion bombardment in the cathode compared with the conventional sputtering system, the process characteristics of the FTS apparatus are investigated under various sputtering conditions such as the distance between two targets (), the distance between the target and the substrate (), and the deposition time. The film by the FTS system can reduce the damage on the films because the ion bombardment with high-energy particles like gamma-electrons, Moreover, the film with optimized condition (

High-efficiency BGaN/AlN quantum wells for optoelectronic applications in ultraviolet spectral region

Light emission characteristics of ultraviolet (UV) BGaN/AlN quantum well (QW) structures were investigated using the multiband effective-mass theory and non-Markovian model. The BGaN/AlN QW structures show a much larger light intensity than the conventional AlGaN/AlN QW structures. This is mainly due to the fact that the internal field is significantly reduced by increasing boron contents. The spontaneous emission peak shows a maximum at the critical value (x= 0.04) and begins to decrease when the boron content is further increased. Hence, we expect that BGaN/AlN QW structures with small boron contents can be used as a TE-polarized light source with a high efficiency in UV region.

Effects of spontaneous polarization on optical properties of ultraviolet BAlGaN/AlN quantum well structures

Effects of spontaneous polarization on electronic and optical properties of ultraviolet (UV) BxAlyGa1-x-yN/AlN quantum well (QW) structures were using the multiband effective-mass theory. The spontaneous emission peak begins to decrease when the boron composition exceeds a critical value. The critical value is found to increase rapidly with decreasing the absolute value of the spontaneous polarization constant. In addition, the light intensity is reduced with decreasing spontaneous polarization. However, the spontaneous emission peak of BAlGaN/AlN QW structures is found to be greatly improved with the inclusion of the boron, irrespective of the spontaneous polarization. Hence, we expect that BAlGaN/AlN QW structures can be used as a high-efficiency light source for optoelectronic applications in ultraviolet spectral region.

Exciton binding energies in wurtzite ZnO/MgZnO quantum wells

The exciton binding energies of ZnO/MgZnO quantum well (QW) structures were investigated by considering piezoelectric (PZ) and spontaneous (SP) polarizations. These results are compared with those of GaN/AlGaN QW lasers. With increasing sheet carrier density, both QW structures show that the exciton binding energy is significantly reduced, suggesting that excitons are nearly bleached at typical densities ( approximately 1013cm-2 ) for which lasing occurs. The flat-band model of the both QW structure shows that, with decreasing well width, the exciton binding energy increases due to the increasing confinement effect in the well. However, the self-consistent model of both QW structures shows that, with the inclusion of the internal field, the exciton binding energy is substantially reduced compared to that of the flat-band value. This is resulted from the smaller overlap due to spatial separation between the conduction and the valence wave functions as the well width gets larger. We also know that the exciton binding energy of ZnO/MgZnO QW structures is much larger than that of GaN/AlGaN QW structures. The larger exciton binding energy observed in ZnO/MgZnO QW structure can be explained by the larger matrix element than the GaN/AlGaN QW stucture, in addition to its smaller dielectric constant.

Dynamics of solitary-waves in the coupled Korteweg-De Vries equations

We find new analytic solitary-wave solutions, having a nonzero background at infinity, of the coupled Korteweg-De Vries equation, using the auxiliary function method. We study the dynamical properties of the solitary-waves by numerical simulations. It is shown that the solitary-waves can be stable or unstable, depending on the coefficients of the model. We study the interaction dynamics by using the solitary-waves as initial profiles to show that the mass and energy of the coupled Korteweg- De Vries can be conserved for a negative third-order dispersion term. - PACS numbers: 03.40.Kf, 02.30.Jr, 47.20.Ky, 52.35.Mw