• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.439-443
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• 2018

The outstanding characteristics of high quality GaN single crystal substrates make it possible to apply the manufacture of high brightness light emitting diodes and power devices. However, it is very difficult to obtain high quality GaN substrate because the process conditions are hard to control. In order to effectively control the formation of GaN polycrystals during the bulk GaN single crystal growth by the HVPE (hydride vapor phase epitaxy) method, a quartz ring was introduced in the edge of substrate. A variety of evaluating method such as high resolution X-ray diffraction, Raman spectroscopy and photoluminescence was used in order to measure the effectiveness of the quartz ring. A secondary ion mass spectroscopy was also used for evaluating the variations of impurity concentration in the resulting GaN single crystal. Through the detailed investigations, we could confirm that the introduction of a quartz ring during the GaN single crystal growth process using HVPE is a very effective strategy to obtain a high quality GaN single crystal.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.10
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• pp.1202-1208
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• 1988

The electron density and electronic states in n- AlGaAs/GaAs heterointerface are calculated by using classical- and quantum-mechanics, respectively. We examine the effects of spacer layer thickness and doping concentration in AlGaAs layer on 2DEG density. Also, the dependences of electronic states of 2DEG upon temperature and acceptor concentration in GaAs layer are investigated.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.149-153
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• 2019

HVPE is one of the GaN single crystal manufacturing methods which has been commercially widely used due to its high growth rate. HVPE method consists of a number of processes, in particular the nitridation of the substrate prior to GaN growth has a significant effect on the crystalline quality of the manufactured GaN single crystal. In this study, we investigated the effect of nitridation for crystalline quality of GaN when it was grown on the sapphire substrate. The whole growth conditions except for the nitridation process were the same, and the gas flow rate supplied to the sapphire substrate was variously changed during the nitridation. Here, we examined the effect of nitridation via the surface characterization of GaN single crystal grown by HVPE.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.4
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• pp.159-165
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• 2018

The demand on use of GaN single crystal substrates for high efficient and environment - friended high power electronic semiconductor has be increased. The industrial business trend on GaN substrate along with its research activities has been reviewed through the recent scientific and technical in formations on the basic of Yole report (2013). The research on the GaN single crystal substrate has been performed continuously for the purpose of the high quality and larger diameter, but its market has not been activated yet.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.83-88
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• 2022

To improve the crystallinity of GaN, there are researches on surface treatment to control the difference in physical properties between GaN and heterogeneous substrate. 'Low-temperature GaN (LT-GaN)' is one of the ways to solve the problem and we investigated the relationship between growth temperature and properties of LT-GaN in our homemade vertical type HVPE. The LT-GaN nuclei were formed on the sapphire surface at low growth temperatures and they presented differences in the density and crystallinity depending on the growth temperature. Significantly, the stress relaxation effect on the epitaxial GaN (epi-GaN) was affected by the crystallinity of LT-GaN. However, the high crystallinity of LT-GaN exacerbated the crystal quality of epi-GaN because they worked as a catalyst and seed of polycrystalline.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.89-93
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• 2017

GaN single crystals were grown by controlling of various processing parameters such as growing temperature, V/III ratio and growing rate. We optimized thickness of bulk GaN single crystal by analyzing defect of surface and inside of the GaN single crystal for application to high brightness and power device. 2-inch bulk GaN single crystals were grown by HVPE (hydride vapor phase epitaxy) on sapphire and their thickness was 0.3~7.0 mm. Crystal structure of the grown bulk GaN was analyzed by XRD (X-ray diffraction). The surface characteristics of the grown bulk GaN were observed by OM (optical microscope) and SEM (scanning electron microscopy) with measuring EPD (etch pits density) of the GaN crystals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.2
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• pp.41-46
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• 2020

The characteristics of the residual stress on the types of the substrate was investigated with adjusting the V/III ratio during GaN growth via the HVPE method. GaN single crystal layers were grown on a sapphire substrate and a GaN template under the conditions of V/III ratio 5, 10, and 15, respectively. During GaN growth, multiple hexagonal pits in GaN single crystal were differently revealed in accordance with growth condition and substrate type, and their distribution and depth were measured via optical microscopy(OM) and white light interferometry(WLI). As a result, it was confirmed that the distribution area and depth of hexagonal pit tended to increase as the V/III ratio increased. Moreover, it was found that the residual stress in GaN single crystal decreased as the distribution area and depth of the pit increased through measuring micro Raman spectrophotometer. In the case of GaN growth according to substrate type, the GaN on GaN template showed lower residual stress than the GaN grown on sapphire substrate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.196-201
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• 2014

We investigated defects and surface polarity in AlN and GaN by using wet chemical etching. Therefore, the effectiveness and reliability of estimating the single crystals by defect selective etching in NaOH/KOH eutectic alloy have been successfully demonstrated. High-quality AlN and GaN single crystals were etched in molten NaOH/KOH eutectic alloy. The etching characteristics and surface morphologies were carried out by scanning electron microscope (SEM) and atomic force microscope (AFM). The etch rates of AlN and GaN surface were calculated by etching depth as a function of etching time. As a result, two-types of etch pits with different sizes were revealed on AlN and GaN surface, respectively. Etching produced hexagonal pits on the metal-face (Al, Ga) (0001) plane, while hexagonal hillocks formed on the N-face. On etching rate calibration, it was found that N-face had approximately 109 and 15 times higher etch rate than the metal-face of AlN and GaN, respectively. The size of etch pits increased with an increase of the etching time and they tend to merge together with a neighbouring etch pits. Also, the chemical mechanism of each etching process was discussed. It was found that hydroxide ion ($OH^-$) and the dangling bond of nitrogen play an important role in the selective etching of the metal-face and N-face.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.6
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• pp.261-264
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• 2012

In this paper, we investigated characteristics of etching induced surface morphology variation by wet etching of GaN epilayer were grown on sapphire (0001) substrate by hydride vapor phase epitaxy (HVPE). As a results of scanning electron microscope (SEM) observation, three types of hexagonal etch pits (Edge, Screw, Mixed) were formed by the GaN epilayer thickness variations. A lot of etch pits, attributed to screw and mixed type TD, were observed at thinner epilayer, leading to high etch pit density. On the other hand, the thickness of GaN epilayer increased with the number of etch pits corresponding to edge and mixed dislocations, which are the majority of TDs are observed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.101-104
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• 2008

GaN films were grown on the vertical and horizontal reactors by the hydride vapour phase epitaxy (HVPE). The structural and optical characteristics of the GaN films were investigated depending on the reactor-type. GaN epilayers were characterized by double crystal X-ray diffraction (DC-XRD), transmission electron microscopy (TEM) and photoluminescence (PL). Surface defects of two kinds of the GaN films were revealed by the wet chemical etching method, using $H_3PO_4$ acid at $200^{\circ}C$ for 8 minutes. Hexagonal etch pits were analyzed by optical microscopy and SEM. Etch pit densities were calculated to be approximately $1.4{\times}10^7$ and $1.2{\times}10^6\;cm^{-2}$ for GaN layers grown on horizontal and vertical reactors, respectively. Those results show GaN grown in the vertical reactor having a better quality of optical properties and crystallinity than that in the horizontal reactor.