Young Jun Choi

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.

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.