• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.273-279
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• 1999

The home-made hot wall epitaxy (HWE) system was utilized for GaN epitaxial layer growth on the Si(001) substrate. It was appeared that GaN epilayer grow with mixed phase of Zinc blende and Wurtzite structure from photoluminescence (PL) and x-ray diffraction (XRD) analysis at the room temperature. We found that intial growth layer has Wurtzite structure from photoluminescence (PL) and x-ray diffractio (XRD) analyses at the room temperature. Wefound that initial growth layer has Wurtzite structure when initial deposition time, the temperature of substrate and source are 4 min, $720^{\circ}C$ and $860^{\circ}C$ respectively, and at the epi growth process GaN, epilayer was grown with relatively stable Wurtzite structure when the temperature of substrate and source are $1020^{\circ}C$ and $910^{\circ}C$ respectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.301-305
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• 2012

In this work the mechanical behaviors of GaN nanowires are analyzed during tension, compression, and unloading deformations. The thermal conductivity of the nanowires at each deformed state is evaluated using an equilibrium Green-Kubo approach. Under tensile loading, the [0001]-oriented nanowires with hexagonal cross-sections undergo a phase transformation from wurtzite to a tetragonal structure. The phase transformation is not observed under compressive loading. The thermal conductivity decreases on going from compressive strains to tensile strains. The strain dependence of the thermal conductivity results from the relaxation time of phonon. A reverse transformation from the tetragonal structure to the wurtzite structure is observed during unloading. The thermal conductivities in the intermediate states are lower than the conductivity in the wurtzite structure at same strain. Such differences in the thermal conductivity between different atomic structures are mainly due to changes in the group velocity of phonon.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.290-291
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• 2005

We have presented a comprehensive effective-mass Hamiltonian for strained Wurtzite semiconductors using k${\cdot}$p method and Kane's model. This theoretical groundwork provides a foundation for investigating the electrical and optical properties of wurtzite strained quantum-well lasers.

• Advances in nano research
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• v.2 no.3
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• pp.157-172
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• 2014

The three-dimensional Nano-Electronic Modeling toolkit (NEMO 3-D) is an open source software package that allows the atomistic calculation of single-particle electronic states and optical response of various semiconductor structures including bulk materials, quantum dots, impurities, quantum wires, quantum wells and nanocrystals containing millions of atoms. This paper, first, describes a software module introduced in the NEMO 3-D toolkit for the calculation of electronic bandstructure and interband optical transitions in nanowires having wurtzite crystal symmetry. The energetics (Hamiltonian) of the quantum system under study is described via the tight-binding (TB) formalism (including $sp^3$, $sp^3s^*$ and $sp^3d^5s^*$ models as appropriate). Emphasis has been given in the treatment of surface atoms that, if left unpassivated, can lead to the creation of energy states within the bandgap of the sample. Furthermore, the developed software has been validated via the calculation of: a) modulation of the energy bandgap and the effective masses in [0001] oriented wurtzite nanowires as compared to the experimentally reported values in bulk structures, and b) the localization of wavefunctions and the optical anisotropy in GaN/AlN disk-in-wire nanowires.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.354-358
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• 1997

Crystal properties of wurtzite GaN films grown on $Al_2O_3$(0001) substrates under various nitrogen pressure and plasma power by electron cyclotron resonance molecular beam epitaxy were investigated by full width at half maximum of X-ray diffraction peak and scanning electron microscope. It was found that the nitrogen pressure has a large effect on the FWHM value of XRD, and the GaN film grown under the optimum nitrogen pressure contains high density of dislocations. These results suggest that the crystal quality is sensitive to the plasma source conditions and that the relaxation of stress depends of V/III ratio. However, substrate-surface nitridation has little effect on the relaxation of misfit stress.

• Journal of Magnetics
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• v.17 no.1
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• pp.13-18
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• 2012

Starting with Kubo's formula and using the projection operator technique introduced by Kawabata, EPR lineprofile function for a $Mn^{2+}$-doped wurtzite structure GaN semiconductor was derived as a function of temperature at a frequency of 9.49 GHz (X-band) in the presence of external electromagnetic field. The line-width is barely affected in the low-temperature region because there is no correlation between the resonance fields and the distribution function. At higher temperature the line-width increases with increasing temperature due to the interaction of electrons with acoustic phonons. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.95-96
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• 2005

The general method and mechanism for the polarity control of heteroepitaxial wurtzite films, such as ZnO and GaN, by interface engineering via plasma-assisted molecular beam epitaxy are addressed. We proposed the principle and method controlling the crystal polarity of ZnO on GaN and GaN on ZnO. The crystal polarity of the lower film was maintained by forming a heterointerfce without any interface layer between the upper and the lower layers. However the crystal polarity could be changed by forming the heterointerface with the interface layer having an inversion center. The principle and method suggested here give us a promising tool to fabricate polarity inverted heterostructures, which applicable to invent novel heterostructures and devices.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.06a
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• pp.84-84
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• 1998

• Journal of the Optical Society of Korea
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• v.12 no.1
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• pp.42-48
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• 2008

The relative intensity noise (RIN) characteristics in 405 nm blue laser diodes grown on wurtzite AlGaInN multiple quantum well structures were investigated using the rate equations with the quantum Langevin noise model. The device parameters were extracted from the optical gain properties of the MQW active region using the self-consistent numerical method developed for calculating the multiband Hamiltonian in the strained wurtzite crystal. These methods have been applied to laser diodes for various conditions including the external feedback and the high frequency current injection.

• Journal of the Korean Magnetic Resonance Society
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• v.25 no.4
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• pp.51-57
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• 2021

We study optical quantum transition line widths in relation to magnetic field dependence properties of the electrons confined in an infinite square well potential system between z = 0 and z = L_z in the z - direction. We consider two systems-one is subject to right circularly oscillating external fields and the other is subject to left circularly oscillatory external fields. Our results indicate that the line widths of right circularly oscillating external fields is larger than the line widths of left, while the opposite result is obtained for the line widths.