• Journal of the Microelectronics and Packaging Society
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• v.18 no.3
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• pp.25-32
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• 2011

We have studied on the slicing and polishing processes of R-plane sapphire wafers for the substrates of UHB nonpolar a-plane GaN LED. The fabrication conditions of the R-plane and c-plane wafers were influenced by the large anisotropic properties (mechanical properties) of the sapphire. The slicing process was more affected by the anisotropic properties of R-plane than the polishing process. When the slicing direction was $45^{\circ}$ to the a-flat, the slicing time was shorter and the quality of as-slicing wafers was better than the slicing direction of normal to the a-flat. The MRR(Material removal rate) of mechanical polishing processes such as lapping and DMP(Diamond mechanical polishing) did not show significant differences between the R-plane and c-plane. The MRR of the c-plane was about two times higher than that of R-planes at the CMP(Chemical mechanical polishing) process due to the formation of hydrolysis reaction layers on the surface of the c-plane.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.636-641
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• 2012

In this study, we have investigated highly efficient nanoscale surface corrugated light emitting diodes (LEDs) for the enhancement of light extraction efficiency (LEE) of nitride semiconductor LEDs. Nanoscale indium tin oxide (ITO) surface corrugations are fabricated by using the conformal nanoimprint technique; it was possible to observe an enhancement of LEE for the ITO surface corrugated LEDs. By incorporating this novel method, we determined that the total output power of the surface corrugated LEDs were enhanced by 45.6% for patterned sapphire substrate LEDs and by 41.9% for flat c-plane substrate LEDs. The enhancement of LEE through nanoscale surface corrugations was studied using 3-dimensional Finite Different Time Domain (FDTD) calculation. From the FDTD calculations, we were able to separate the light extraction from the top and bottom sides of device. This process revealed that light extraction from the top and bottom sides of a device strongly depends on the substrate and the surface corrugation. We found that enhanced LEE could be understood through the mechanism of enhanced light transmission due to refractive index matching and the increase of light scattering from the corrugated surface. LEE calculations for the encapsulated LEDs devices also revealed that low LEE enhancement is expected after encapsulation due to the reduction of the refractive index contrast.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.41-47
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• 1999

Ion implanted GaAs MESFET with low resistive layer was fabricated using Si diffusion into GaAs from SiN. During the thermal annealing at 95$0^{\circ}C$ for 30s, Si diffused into ion implanted region of GaAs from SiN and they formed low resistive layer of 350$\AA$ thickness. The diffusion of Si decreased the sheet resistance of source and drain region from 1000$\Omega$/sq. to 400$\Omega$/sq. and the AuGe/Ni/Au ohmic contact resitivity from 2.5$\times$10sub -6$\Omega$-cmsup 2 to $1.5\times$10sup -6$\Omega$-cmsup 2. The fabricated lum gate length MESFET with Si diffused surface layer shows the transconductance of 360ms/mm, 8.5dB of associated gain and 3.57dB of minimum noise figure at 12GHz. These performances are better than that of MESFET without Si diffused layer.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.4
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• pp.80-85
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• 2007

The passivation is one of the important technologies for protection of the devies from damage. In this paper, we fabricated $0.1{\mu}m\;{\Gamma}$--gate InAIAs/InGaAs metamorphic high electron mobility transistors (MHEMTs) on a GaAs substrate. And then the wafer with MHEMTs was divided into two pieces; one for passivation and another for without passivation experiments. The passivations were done by using both low-k BCB and Si3N4 thin films. DC and RF performances were measured and the results are compared. The MHEMTs with BCB passivation show lower degradation than ones with Si3N4 passivation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.11-20
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• 1994

GaAs and AlGaAs epi-layers were grown on semi-insulating (100) GaAs substrate by molecular beam epitaxy (MBE) and their electrical and optical properties have been investigated by several measurements. In undoped GaAs, the p-type GaAs layers with the good surface morphology were obtained under the growth conditions of the substrate temperatures ranging from 570 to $585^{\circ}C$ and the $As_4$/Ga ratios from 17 to 22. In the samples with the growth rates of the ranges of $0.9~1.1 {\mu}m/h$, the impurity concentrations were in the ranges of $1.5{\times}10^{14}~5.6{\times}10^{14}cm^{-3}$ with the Hall mobilities of $590~410cm^2/V-s$. In the Si-doped GaAs, the n-type GaAs layers with low electro trap, only two hole deep levels were observed with uniform doping profiles (<1%). AlGaAs layers with good surface morphology and crystallinity were grown under an optimum condition of the substrate temperature, $600^{\circ}C $. 8 deep level defects were observed between 0.17~0.85eV in undoped AlGaAs layers.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.116-121
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• 2000

The temperature profiles of gas phase and the concentration profiles of GaN precursors in an inverted OMVPE reactor have been carried out by in-situ Raman spectroscopy. Pure rotational Raman scattering from the carrier gas (rd) was used to determine the temperature profiles in the reactor, and a large temperature gradient perpendicular the susceptor surface was observed. The homogeneous gas phase decompositions of the OMVPE precursors were investigated by the vibrational Raman spectra, and it was found that the pyrolyses of $NH_3$ and TMGa begin above 800 K and 650 K, respectively, but a noticeable amount of precursors remain undecomposed even in the region very close to the susceptor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.252-255
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• 2004

Various Semiconductor/Metal structured nanowires were synthesized from the simple thermal annealing of ball-milled compound powders and the thermal evaporation of metals. Their structural properties were investigated by Scanning Electron Microscopy(SEM) and Transmission Electron Microscopy(TEM), Energy Dispersive X-ray spectroscopy(EDX). Depending on the type of metals and the material of nanowires, uniform somiconductor/metal nanowires(GaN/Al, GaN/Ag) or isolated metal particles on semiconductor nanowires$(SnO_2/Ti,\;Si/Ti)$ were formed on the surface of nanowires.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.219-224
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• 2001

Pd/Ge/Ti/Pt ohmic contact to n-type InCaAs was investigated. Minimum specific contact resistivity of $3.7\times10^{-6}\; \Omega\textrm{cm}^2$ was achieved by rapid thermal annealing at $400^{\circ}C$ for 10 seconds. This was related to the formation of Pd-Ge compounds and the in-diffusion of Ge atoms to InGaAs surface. However, the specific contact resistivity increased slightly to $low-10^5\; \Omega\textrm{cm}^2$ in the case of longer annealing time. Superior ohmic contact and non-spiking planar interface between ohmic materials and InGaAs were maintained after annealing at high temperature. Therefore, this thermally stable ohmic contact system is a promising candidate for compound semiconductor devices.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.575-580
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• 2012

The purpose of this study is to investigate the crystalline structure and optical properties of (GaZn)(NO) powders prepared by solid-state reaction between GaOOH and ZnO mixture under $NH_3$ gas flow. While ammoniation of the GaOOH and ZnO mixture successfully produces the single phase of (GaZn)(NO) solid solution within a GaOOH rich composition of under 50 mol% of ZnO content, this process also produces a powder with coexisting (GaZn)(NO) and ZnO in a ZnO rich composition over 50 mol%. The GaOOH in the starting material was phase-transformed to ${\alpha}$-, ${\beta}-Ga_2O_3$ in the $NH_3$ environment; it was then reacted with ZnO to produce $ZnGa_2O_4$. Finally, the exchange reaction between nitrogen and oxygen atoms at the $ZnGa_2O_4$ powder surface forms a (GaZn)(NO) solid solution. Photoluminescence spectra from the (GaZn)(NO) solid solution consisted of oxygen-related red-emission bands and yellow-, green- and blue-emission bands from the Zn acceptor energy levels in the energy bandgap of the (GaZn)(NO) solid solutions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.2
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• pp.45-50
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• 2022

Ga₂O₃ thin films were grown on n-type Si substrates at various growth temperatures of 500, 550, 600, 650 and 700℃. The Ga₂O₃ thin films grown at 500℃ and 550℃ were characterized as featureless flat surface. Grown at higher temperatures (600, 650, and 700℃) showed very rough surface morphology. To figure out the annealing effect on the thin films grown at relatively low temperatures (500, 550, 600, 650 and 700℃), the Ga₂O₃ films were thermally treated at 900℃ for 10 minutes. Crystal structure of the Ga₂O₃ films grown at 500 and 550℃ were changed from amorphous to polycrystalline structure with flat surface. Ga₂O₃ film grown at 550℃ was chosen for the fabrication of a Schottky barrier diode (SBD). Electrical properties of the SBDs depend on the thermal treatment were evaluated. A MSM type photodetector was made on the low temperature grown Ga₂O₃ thin film. The photocurrent for the illumination of 266 nm wavelength showed 5.32 times higher than dark current at the operating voltage of 10 V.