H. Naoi

Epitaxial lateral overgrowth of GaN on selected-area Si(1 1 1) substrate with nitrided Si mask

Abstract Epitaxial lateral overgrowth (ELO) of GaN by metalorganic vapor phase epitaxy was carried out on Si substrates using new ELO-mask patterns. The groove or SiO 2 mask pattern employed was a stripe in combination with a larger period grid (100xa0μm×100xa0μm): the former is for the ELO of the GaN to reduce the threading dislocation (TD) density and the latter is for limiting the area of growth and to suppress the formation of cracks in the grown GaN. Crack-free GaN layers with a reduced TD density were successfully obtained for both types of Si substrate, i.e., the grooved Si substrate and the SiO 2 -masked Si substrate. The properties of GaN layers grown on these Si substrates are compared.

Growth of Crack‐Free and High‐Quality AlGaN with High Al Content Using Epitaxial AlN (0001) Films on Sapphire

High-quality AlGaN with high Al content was grown on high-quality epitaxial AlN film on sapphire (0001) by low-pressure metal organic vapour phase epitaxy (LP-MOVPE). The obtained Al x Ga 1-x N (0.2 < x < 0.8) thicker than 0.9 μm had atomically smooth surface without any cracks. Full width at half maximum (FWHM) values of X-ray rocking curve (XRC) from the AlGaN were less than 200 arcsec for (0002) diffraction. It is considered that in-plane compressive stress in the AlGaN due to larger in-plane lattice constant of the AlGaN than that of the underlying AlN plays an important role in restraining generation of cracks.

High Quality GaN Grown by Facet‐Controlled ELO (FACELO) Technique

We fabricated high-quality GaN by low-pressure metalorganic vapour phase epitaxy (LP-MOVPE) using Facet Controlled Epitaxial Lateral Overgrowth (FACELO) technique. Density and distribution of threading dislocations (TDs) in the GaN epitaxial layer strongly depended on the ELO mask and window widths, and were related to facet structures during the ELO process. It was found that tilt and twist of c-axis in the FACELO GaN were very small. Low temperature cathodoluminescence (CL) spectra of the FACELO GaN with low TD density exhibited excellent crystallographic quality.

High Quality GaN Grown by Raised-Pressure HVPE

Effects of reactor pressure on growth of GaN by hydride vapour phase epitaxy (HVPE) have been investigated. For growth at 0.4 atm for 1 h, a large number of cracks were observed in GaN layers with the thickness about 30 μm and the FWHM values in (0004) and (10-10) X-ray rocking curves (XRCs) were larger than 350 arcsec. For growth at 1.2 atm for 1 h, GaN layers with the thickness about 60 μm were free from cracks and the FWHMs in both (0004) and (10-10) XRC were dramatically reduced to narrower than 200 arcsec.

Distribution of Threading Dislocations in Epitaxial Lateral Overgrowth GaN by Hydride Vapor-Phase Epitaxy Using Mixed Carrier Gas of H2 and N2

Distribution of threading dislocations (TDs) in epitaxial lateral overgrowth (ELO) GaN by hydride vapor-phase epitaxy (HVPE) has been investigated. Two types of carrier gas, i.e., N2 and H2+N2, were used in the HVPE in order to change the facet structure of the ELO layer. Results of cathodoluminescence (CL) mapping and HCl vapor-phase etching revealed lower TD density in the ELO layer grown using the H2+N2 mixed carrier gas than that using the N2 carrier gas.

Fabrication and Optical Characterization of Facet-Controlled ELO (FACELO) GaN by LP-MOVPE

The fabrication and characterization of GaN grown by metalorganic vapor phase epitaxy (MOVPE) using Facet Controlled Epitaxial Lateral Overgrowth (FACELO) technique were carried out. The density and distribution of threading dislocations (TDs) in the GaN epitaxial layer strongly depended on the ELO mask and window widths, and were related to facet structures during the ELO process. It was found that tilt and twist of c-axis in the FACELO GaN was very small. The temperature dependence of PL spectra of the FACELO GaN exhibits that the quality of the crystal is fairly good.