Mi-Seon Park

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.

Crystal structure investigation of AlN crystal grown on 6H-SiC seed by a physical vapor transport method

The effect of process parameters such as the growth pressure and temperature on the AlN crystal growth has been investigated. AlN crystal was grown onto 6H-SiC seed crystal using PVT (Physical Vapor Transport) method. Crystal properties and morphology of AlN crystal was changed with growth pressure and temperature. Raman analysis confirmed that AlN crystals with different orientation were successfully grown on SiC seed crystal.

The role of porous graphite plate for high quality SiC crystal growth by PVT method

The present research is focused on the effect of porous graphite what is influenced on the 4H-SiC crystal growth by PVT method. We expect that it produces more C-rich and a change of temperature gradient for polytype stability of 4H-SiC crystal as adding the porous graphite in the growth cell. The SiC seeds and high purity SiC source materials were placed on opposite side in a sealed graphite crucible which was surrounded by graphite insulator. The growth temperature was around and the growth pressure was 10~30 Torr of an argon pressure with 5~15 % nitrogen. 2 inch off-axis 4H-SiC with C-face (000-1) was used as a seed material. The porous graphite plate was inserted on SiC powder source to produce a more C-rich for polytype stability of 4H-SiC crystal and uniform radial temperature gradient. While in case of the conventional crucible, various polytypes such as 6H-, 15R-SiC were observed on SiC wafers, only 4H-SiC polytype was observed on SiC wafers prepared in porous graphite inserted crucible. The defect level such as MP and EP density of SiC crystal grown in the conventional crucible was observed to be higher than that of porous graphite inserted crucible. The better crystal quality of SiC grown using porous graphite plate was also confirmed by rocking curve measurement and Raman spectra analysis.

Seed Crystal Surface Properties for Polytype Stability of SiC Crystals Growth

SiC crystal ingots were grown on 6H-SiC dual-seed crystals with different surface roughness and different seed orientation by a PVT (Physical Vapor Transport) method. 4H and 15R-SiC were grown on seed crystal with high root-mean-square (rms) value. The polytype of grown crystal on the seed crystal with lower rms value was confirmed to be 6H-SiC. On the other hand, all SiC crystals grown on seed crystals with different seed orientation were proven to be 6H-SiC. The surface roughness of seed crystals had no effect on the crystal structure of the grown crystals. However, the crystal quality of 6H-SiC single crystals grown on the on-axis seed were revealed to be slightly better than that of 6H-SiC crystal grown on the off-axis seed.

The Characteristics of Mg 0.1 Zn 0.9 O Thin Films on PES Substrate According to Fabricated Conditions by PLD

Concern for the TOS (Transparent Oxide Semiconductor) is increasing with the recent increase in interest for flexible device. Especially MgZnO has attracted a lot of attention. , which ZnO-based wideband-gap alloys is tuneable the band-gap ranges from 3.36 eV to 7.8 eV. In particular, the flexible substrate, the crystal structure of the amorphous as well as the surface morphology is not good. So research of MgZnO thin films growth on flexible substrate is essential. Therefore, in this study, we studied on the effects of the oxygen partial pressure on the structural and crystalline of thin films. MgZnO thin films were deposited on PES substrate by using pulsed laser deposition. We used XRD and AFM in order to observe the structural characteristics of MgZnO thin films. UV-visible spectrophotometer was used to get the band gap and transmittance. Crystallization was done at a low oxygen partial pressure. The crystallinity of MgZnO thin films with increasing temperature was improved, Grain size and RMS of the films were increased. MgZnO thin films showed high transmittance over 80% in the visible region.

Effect of Oxygen Pressure on the Structure Properties of Mg 0.5 Zn 0.5 O Thin Films Grown by Pulsed Laser Deposition

In this work, we study on the effects of the oxygen pressure on the structural and crystalline of MgZnO thin films. MgZnO thin films were deposited on p-Si (111) substrates by using pulsed laser deposition. The X-ray diffraction analysis and energy-dispersive X-ray results revealed that as the oxygen pressure increased and Mg content in the MgZnO films decreased. Also Crystal structure was changed from cubic rock salt to hexagonal wurtzite. Alpha step and atomic force microscopy results showed that the thickness of the films are about 100 nm, and it has been found that the MgZnO (002) preferred orientation were deposited with increasing the oxygen pressure. Therefore, the effect of the preferred orientation, the crystallization grew in the form of the columnar; Grain size and RMS of the films were increased with increasing oxygen pressure.

The Polytype Transformation Research During SiC Crystal Growth by the Effect of Doping Level in Seed

In this study, SiC single-crystal ingots were prepared on two seed crystals with different doping level by using the physical vapor transport (PVT) technique; then, SiC crystal wafers sliced from the grown SiC ingot were systematically investigated to find the effect of seed doping level on the doping concentration and crystal quality of the SiC. To exclude extra effects induced by adjustment of the process parameters, we simultaneously grew the SiC crystals on two seed crystals with different level, which were fabricated from previous two SiC crystal ingots.

Effect of Thickness on the Properties of Al Doped ZnO Thin Films Deposited by Using PLD

AZO (Al doped ZnO) thin films were deposited on the quartz substrates with thickness variation from 25 to 300 nm by using PLD (pulsed laser deposition). XRD (x-ray diffractometer), SPM (scanning probe microscopy), Hall effect measurement and uv-visible spectrophotometer were employed to investigate the structural, morphological, electrical and optical properties of the thin films. XRD results demonstrated that films were preferrentially oriented along the c-axis and crystallinity of film was improved with increase of film thickness. As for the surface morphologies, the mean diameter and root mean square of grains were increased as the film thickness was increased. When the film thickness was 200 nm, the lowest resistivity of obtained with carrier concentration of and mobility of . All samples showed more than 80% of transmittance in the visible range. Upon these results, it is found that the samples thickness can affect their structural, morphological, optical and electrical properties. This study suggests that the resistivity can be improved by controlling film thickness.