• Korean Journal of Materials Research
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• v.12 no.4
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• pp.304-307
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• 2002

A zinc oxide (ZnO) single crystal was used as a substrate in the hydride vapor-phase epitaxy (HVPE) growth of GaN and the structural and optical properties of GaN layer were characterized by x- ray diffraction, transmission electron microscopy, secondary ion mass spectrometry, and photoluminescence (PL) analysis. Despite a good lattice match and an identical structure, ZnO is not an appropriate substrate for application of HVPE growth of GaN. Thick film could not be grown. The substrate reacted with process gases and Ga, being unstable at high temperatures. The crystallinity of ZnO substrate deteriorated seriously with growth time, and a thin alloy layer formed at the growth interface due to the reaction between ZnO and GaN. The PL from a GaN layer demonstrated the impurity contamination during growth possibly due to the out-diffusion from the substrate.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.170-170
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• 2003

We have implanted on sapphire substrate with various ions and investigated the properties of GaN epilayers grown on implanted sapphire substrate by metal organic chemical vapor deposition (MOCVD). Sapphire is typical substrate for GaN epilayers. However, there are many problems such as lattice mismatch and thermal coefficient difference between sapphire substrate and GaN. The ion implanted substrate's surface had decreased internal tree energies during the growth of the GaN epilayer, md the misfit strain was relieved through the formation of an AlN phase on the ions implanted sapphire(0001) substrates. [1] The crystal and optical properties of GaN epilayer grown in ions implanted sapphire(0001) substrate were improved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.11
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• pp.702-706
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• 2016

We demonstrated that self-separation FS-GaN (freestanding-GaN) was grown on MELO (maskless epitaxially lateral overgrowth) GaN template by horizontal HVPE (hydride vapor phase epitaxy). Before thick GaN grwoth, MELO GaN template was grown on patterned GaN template by MOCVD (metal organic chemical vapor deposition). The laterally overgrown GaN would consist of a continuous well coalesced layer. The mixed TDD (threading dislocation density) of seed and wing region were $8{\times}10^8cm^{-2}$ and $7{\times}10^7cm^{-2}$, respectively. After thick GaN grown by HVPE, the self-separation between thick GaN and sapphire substrate was generated at seed region. The regions of self-separation for FS-GaN and sapphire were observed by FE-SEM. Moreover, Raman results indicated that the compressive strain of seed and wing regions at FS-GaN substrate were slightly released compared to that of thick GaN grown on conventional GaN template. The optical properties of the FS-GaN substrate were examined by using PL (photoluminescence). The PL exhibited that donor bound exciton and donor acceptor pair were observed at low temperature. The effects on optical and structural properties of FS-GaN substrate have been discussed in detail.

• Journal of the Korean Vacuum Society
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• v.11 no.1
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• pp.50-58
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• 2002

The growth of GaN films on Si substrate has many advantages in that Si is less expensive than sapphire substrate and that integration of GaN-based devices with Si substrate is easier The difference of lattice constant and thermal expansion coefficient between GaN and Si is larger than those between GaN and sapphire. However, which results in many defects into the grown GaN. In order to obtain high duality GaN films on Si substrate, we need to reduce defects using the buffer layer such as AlN. In this study, we prepared three types of AlN buffer layer with various crystallinity on Si (111) substrate using MOCVD, Sputtering and MOMBE methods. GaN was grown by MOCVD on three types of AlN/Si substrate. Using TEM and XRD, we carried out comparative investigation of growth and properties of GaN deposited on the various AlN buffers by characterizing lattice coherency, crystallinity, growth orientation and defects formed (voids, stacking faults, dislocations, etc). It is found that the crystallinity of AlN buffer layer has strong effects on growth of GaN. The AlN buffer layers grown by MOCVD and MOMBE showed the reduction of out-of-plane misorientation of GaN at the initial growth stage.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.51-51
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• 2010

Group III-nitride semiconductors have been widely studied as the materials for growth of light emitting devices. Currently, GaN devices are predominantly grown in the (0001) c-plane orientation. However, in case of using polar substrate, an important physical problem of nitride semiconductors with the wurtzite crystal structure is their spontaneous electrical polarization. An alternative method of reducing polarization effects is to grow on non-polar planes or semi-polar planes. However, non-polar and semipolar GaN grown onto r-plane and m-plane sapphire, respectively, basically have numerous defects density compared with c-plane GaN. The purpose of our work is to reduce these defects in non-polar and semi-polar GaN and to fabricate high efficiency LED on non/semi-polar substrate. Non-polar and semi-polar GaN layers were grown onto patterned sapphire substrates (PSS) and nano-porous GaN/sapphire substrates, respectively. Using PSS with the hemispherical patterns, we could achieve high luminous intensity. In case of semi-polar GaN, photo-enhanced electrochemical etching (PEC) was applied to make porous GaN substrates, and semi-polar GaN was grown onto nano-porous substrates. Our results showed the improvement of device characteristics as well as micro-structural and optical properties of non-polar and semi-polar GaN. Patterning and nano-porous etching technologies will be promising for the fabrication of high efficiency non-polar and semi-polar InGaN LED on sapphire substrate.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.494-499
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• 2004

The structural, electrical and optical properties of GaN epilayers grown on various ion-implanted sapphire(0001) substrates by MOCVD were investigated. Sapphire substrates have been widely adopted to grow high quality GaN epilayer despite the large differences of lattice constant and thermal expansion coefficient between them. So, GaN or AlN buffer layer and pre-treatment was indispensably introduced before the GaN epilayer growth. The ion-implanted substrate's surface had decreased internal free energies during the growth of the ions implanted sapphire(0001) substrates. The crystal and optical properties of GaN epilayers grown in ions implanted sapphire(0001) substrate were improved. Also, excessively roughened and modified surface by ions degraded the GaN epilyers. Not only the ionic radius but also the chemical species of implanted sapphire(0001) substrates could improve the properties of GaN epilayers grown by MOCVD. This result implies that higher quality of GaN epilayers was achieved by using ion-implanted sapphire(0001) substrate with various ions.

• Journal of Ceramic Processing Research
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• v.13 no.spc1
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• pp.128-131
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• 2012

The selective area growth light emitting diode on GaN substrate was grown using mixed-source HVPE method with multi-sliding boat system. The GaN substrate was grown using mixed-source HVPE system. Te-doped AlGaN/AlGaN/Mg-doped AlGaN/Mg-doped GaN multi-layers were grown on the GaN substrate. The appearance of epi-layers and the thickness of the DH was evaluated by SEM measurement. The DH metallization was performed by e-beam evaporator. n-type metal and p-type metal were evaporated Ti/Al and Ni/Au, respectively. At the I-V measurement, the turn-on voltage is 3 V and the differential resistance is 13 Ω. It was found that the SAG-LED grown on GaN substrate using mixed-source HVPE method with multi-sliding boat system could be applied for developing high quality LEDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.7-11
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• 2011

Sapphire substrate was patterned by a selective chemical wet etching technique, and GaN/InGaN structures were grown on this substrate by MOVPE (Metal Organic Vapor Phase Epitaxy). The surface of grown GaN on patterned sapphire substrate (PSS) has good morphology and uniformity. The patterned sapphire substrate LED showed better light output than conventional LED that improvement 50%. We think these results come from enhancement of internal quantum efficiency by decrease of threading dislocation and increase of light extraction efficiency. Also these LED showed more uniform emission distribution in angle than conventional LED.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.194-197
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• 1997

A hydride vapor phase epitaxy (HVPE) method was performed to prepare the thick-fi lm GaN on AIN/Si substrates. We obtained substrate-free GaN. The foul t-width at half maximum of double crystal X-ray rocking curve from 350 ${\mu}{\textrm}{m}$ thick substrate-free GaN was ~1000 arcsec. The photoluminescence spectrum (at 20 K) shows the narrow bound exiton (I$_2$) line and wealth donor-acceptor pair recombination however. there was not observed deep donor-accepter pair recombination indicate the substrate-free GaN crystal prepared in this study are of high purity and high crystalline quality.

• 전자공학회논문지 IE
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• v.43 no.2
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• pp.7-10
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• 2006

A GaN-based metal-insulator-semiconductor (MIS) structure has been fabricated by using $BaTa_2O_6$ instead of conventional oxide as insulator gate. The leakage current o) films are in order of $10^{-12}-10^{-13}A/cm^2$ for GaN on $Al_2O_3$(0001) substrate and in order of $10^{-6}-10^{-7}A/cm^2$ for GaN on GaAs(001) substrate. The leakage current of thses films is governed by space-charge-limited current over 45 MV/cm in case of GaN on $Al_2O_3$(0001) substrate and by Poole-Frenkel emission in case of GaN on GaAs(001).