Hae-Yong Lee

Effects of the V/III ratio on a-plane GaN epitaxial layer on r-plane sapphire grown by HVPE

Department of Materials and Component Engineering, Electronic Ceramics Center, Dong-Eui University, Busan 614-714, Korea*LumiGNtech Co., Ltd., Room 206, Business Incubator Building, Seoul 153-801, Korea(Received June 5, 2014)(Revised June 16, 2014)(Accepted June 18, 2014)Abstract In this study, effects of the V/III ratio on a-plane GaN epitaxial on r-plane grown by HVPE have beeninvestigated. According to increasing of V/III ratio, the value of FWHM of a-plane (11-20) GaN and the value of surfaceroughness (Ra) were decreased. Growth rate of a-plane GaN epitaxial layer were increased until V/III ratio = 7 as theincreasing of V/III ratio, but it was reduced at V/III ratio = 10. At V/III ratio = 10, the FWHM of a-plane (11-20) GaN RCand the surface roughness (Ra) were 829 arcsec and 1.58 nm, respectively, as the lowest value in this study. Also for V/IIIratio = 10, cracks under surface or voids were observed the lowest values in images of optical microscope. An M-shapedazimuthal dependence over 360

The effects of growth temperatures and V/III ratios at 1000℃ for a-plane GaN epi-layer on r-plane sapphire grown by HVPE

The effects of the growth temperature on the properties of a-plane GaN epi-layer on r-plane sapphire by HVPE were studied, when the constant V/III ratio and the flow rate of HCl for the Ga source channel was fixed at 10 and 700 sccm, respectively. Additionally the effects of V/III ratios for source gasses were studied when growth temperature and the flow rate of HCl for the Ga source channel was fixed at 1000 C and 700 sccm, respectively. As the growth temperature was increased, the values of Full Width Half Maximum (FWHM) for Rocking curve (RC) of a-plane GaN (11-20) epi- layer were decreased and thickness of a-plane GaN epi-layer were increased. As V/III ratios were increased at 1000 C, the values of FWHM for RC of a-plane GaN (11-20) were declined and thickness of a-plane GaN epi-layer were increased. The a-plane GaN (11-20) epi-layer grown at 1000 C and V/III ratio = 10 showed the lowest value FWHM for RC of a- plane GaN (11-20) for 734 arcsec and the smallest dependence of Azimuth angle for FWHM of (11-20) RCs.

Properties of GaN Film Grown on AlN/PSS Template by Hydride Vapor Phase Epitaxy

LumiGNtech Co., SK Techno Park, Gwangmyeong 14322, Korea(Received March 31, 2016; Revised May 24, 2016; Accepted May 24, 2016) Abstract: In this paper, GaN film was grown on AlN/PSS by hydride vapor phase epitaxy compared with GaN on planar sapphire. Thin AlN layer for buffer layer was deposited on patterned sapphire substrate (PSS) by metal organic chemical vapor deposition. Surface roughness of GaN/AlN on PSS was remarkably decreased from 28.31 to 5.53 nm. Transmittance of GaN/AlN grown on PSS was lower than that of planar sapphire at entire range. XRD spectra of GaN/AlN grown on PSS corresponded the wurzite structure and c-axis oriented. The full width at half maximum (FWHM) values of ω-scan X-ray rocking curve (XRC) for GaN/AlN grown on PSS were 196 and 208 arcsec for symmetric (0 0 2) and asymmetric (1 0 2), respectively. FWHM of GaN on AlN/PSS was improved more than 50% because of lateral overgrowth and AlN buffer effect.Keywords: GaN, PSS, HVPE, Refractive indexx1d./0 갈륨 나이트라이드 (gallium nitride, GaN)는 1990년 이후로 꾸준히 많이 연구가 이루어지고 있는 반도체 재료이다. 광전자기기인 레이저 다이오드 (laser diode)와 발광 다이오드 (light emitting diode)에 적합한 재료이다. 3.4 eV의 넓은 밴드갭 에너지, 높은 열안정성, 열전도도의 물성을 가지고 있어 고온에서 작

Control of Bowing in Free-standing GaN Substrate by Using Selective Etching of N-polar Face

In this paper, we report that selective etching on N-polar face by EC (electro-chemical)-etching effect on the reduction of bowing and strain of FS (free-standing)-GaN substrates. We applied the EC-etching to concave and convex type of FS-GaN substrates. After the EC-etching for FS-GaN, nano porous structure was formed on N-polar face of concave and convex type of FS-GaN. Consequently, the bowing in the convex type of FS-GaN substrate was decreased but the bowing in the concave type of FS-GaN substrate was increased. Furthermore, the FWHM (full width at half maximum) of (1 0 2) reflection for the convex type of FS-GaN was significantly decreased from 601 to 259 arcsec. In the case, we confirmed that the EC-etching method was very effective to reduce the bowing in the convex type of FS-GaN and the compressive stress in N-polar face of convex type of FS-GaN was fully released by Raman measurement.

Effect of the Control of Bowing in Free-standing GaN by Mechanical Polishing

In this paper, we have studied the effect of mechanical polishing to Ga-polar face for reducing the wafer bowing and strain in free-standing GaN. After the mechanical polishing to Ga-polar face, the bowing of the free-standing GaN substrate significantly decreased with increasing the size of diamond slurry, and eventually changed the bowing direction from concave to convex. Furthermore, the full width at half maximum (FWHM) of high-resolution X-ray diffraction (HR-XRD) were decreased, especially the FWHM of (1 0 2) reflection for 1.0 μm size of diamond slurry was significantly decreased from 630 to 203 arcsec. In the case, we confirmed that the compressive strain in Ga-polar face was fully released by Raman measurement.

Effect of V/III Ratio Variation on the Properties of AlN Epilayers in HVPE

AlN epilayers were grown on a c-plane sapphire substrate using hydride vapor phase epitaxy (HVPE). A series of AlN epilayers were grown at 1120˚C with V/III ratios 1.5, 2.5 and 3.5, and the influence of V/III ratio on their properties was investigated. As the V/III ratio was increased, the surface roughness (RMS roughness), Raman shift of E2 high peaks and full-width at half-maximum (FWHM) of symmetrical (002) & asymmetrical (102) of the AlN epilayers increased. However, the intensities of the Raman E2 high peaks were reduced. This indicates that the crystal quality of the grown AlN epilayers was degraded by activation of the parasitic reaction as the V/III ratio was increased. Smooth surface, stress free and high crystal quality AlN epilayers were obtained at the V/III ratio of 1.5. The crystal quality of AlNepilayers is worsened by the promotion of three-dimensional (3D) growth mode when the flow of NH3 is high.