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Busan, South Korea

Lee S.C.,Jeju National University | Ahn H.S.,Korea Maritime University | Kwon S.H.,Andong National University | Kim S.W.,Andong National University
Physica B: Condensed Matter | Year: 2012

A finite type-I superlattice with different dielectric media on either side of the surfaces is considered under a perturbing electric fields parallel to the superlattice axis on the basis of an infinite square potential well. Using the random-phase approximation, the density-density correlation function including intra- and inter-level transitions in a multiple-quantum-well (MQW) is calculated. The dispersion relations for the surface and the bulk states are obtained as functions of the momentum wave vector and the averaged electric field strength over the quantum well. The Raman intensities due to the bulk and the surface plasmons for the intra- and the inter-level transitions are also obtained for incoming light energy. © 2012 Elsevier B.V. All rights reserved.

Park S.-H.,Catholic University of Daegu | Shim J.-I.,Hanyang University | Yi S.N.,Korea Maritime University
Journal of Applied Physics | Year: 2010

Electronic properties of compressively strained InGaAs/InP vertically stacked multiple quantum wires were investigated using an six-band strain-dependent kp Hamiltonian. The strain tensor ∈yy (∈xx) is found to relax from its initial strain. The amount of relaxation is dependent on the number of wire layers in the vertical stack and increases with the number of wire layers. The interband transition energy also decreases with the number of wire layers. This is mainly attributed to the decrease in the conduction band energy because subband energies in the valence band are nearly independent of the strain. The matrix element is shown to slightly decrease with increasing number of the wire layer in the vertical stack. © 2010 American Institute of Physics.

Lee S.C.,Jeju National University | Ahn H.S.,Korea Maritime University | Kim S.W.,Andong National University
New Physics: Sae Mulli | Year: 2015

In this paper, the density-density correlation function for an n-Ge/SiO2 type-I superlattice with an infinite confining potential well and surfaces of different dielectric media under a perturbing electric field parallel to the superlattice axis is calculated. This includes intrasubband and intersubband transitions in a multiple quantum well (MQW) consisting of n-Ge quantum wells separated by a SiO2 barrier, and the random-phase approximation is used. We also obtain the dispersion relations for the bulk and the surface subband states as functions of the electric field strength averaged over the quantum well and the momentum wavevector, respectively. Furthermore, we obtain the Raman intensities due to the bulk and the surface states of the intrasubband and the intersubband states as a function of the energy of the incident light.

Shin M.J.,Korea Maritime University | Kim M.J.,Korea Maritime University | Jeon H.S.,Korea Maritime University | Ahn H.S.,Korea Maritime University | And 4 more authors.
Japanese Journal of Applied Physics | Year: 2012

We studied GaN nanorods grown by hydride vapour phase epitaxy processes to identify optimal growth conditions that yield nanorods appropriate for use in nanodevices. The growth temperature was varied over the range 625-670°C, and the morphology of the samples changed with increasing growth temperature. GaN nanorods formed at growth temperatures of 645°C on a Si(111) substrate. At a fixed growth temperature of 645°C, the HCl:NH 3 gas flow ratio was adjusted from 1 : 37 to 1 : 41. GaN nanorods with a small diameter of 26nm formed at a HCl:NH 3 ratio of 1 : 38. Individual GaN nanorods clearly grew along the axial direction, perpendicular to the substrate. Cathodoluminescence measurements at room temperature revealed a red shift as the acceleration energy was increased to 15 keV, possibly associated with the internal electric field. © 2012 The Japan Society of Applied Physics.

Shin M.J.,Korea Maritime University | Gwon D.-O.,Korea Maritime University | Lee G.S.,Korea Maritime University | Ahn H.S.,Korea Maritime University | And 2 more authors.
Journal of Luminescence | Year: 2014

We fabricated hybrid structures using combined properties of organic and inorganic materials for application in light emitting diode. The hybrid structures were demonstrated using poly[2-methoxy-5-(3′,7′- dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as organic materials and n-GaN as inorganic materials. To investigate the effects of organic layer thickness, we changed polymer concentration and spin speed of MDMO-PPV solution. We obtained current rectifying behaviour with MDMO-PPV layer of approximate 60 nm thickness. The hybrid structure shows broad emissions covering orange range in both photoluminescence and electroluminescence spectra and its band structures matched well with energy band gap of GaN and MDOM-PPV. We expect the potential applications and the enhanced efficiency in optoelectronic devices with hybrid structure by making progress the results. © 2013 Elsevier B.V.

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