To develop porous Si as substrate for better quality GaN layer
In this work, we prepare porous Si substrates via anodic etching process. The etching parameters such as time and current would be optimized for the best porous substrate, which is defined by having high porous density. The estimated average of porous density of the substrate is determined through the observation via scanning electron microscopy (SEM). After that, a thin GaN film is deposited onto the best porous Si substrate, using RF-sputtering machine. The grown layer is then will be characterized by photoluminescence (PL), X-ray diffraction (XRD) and Hall-effect measurements. As a comparison, we also grow and characterize a thin GaN on non-porous Si substrate, with the adoption of AlN buffer layer.
High quality GaN layers on Si(111) substrates: AlN buffer layer optimisation and insertion of a SiN intermediate layer
We present a study on the material properties of GaN films grown on (111) silicon substrates by low-pressure metalorganic chemical vapour deposition using AlN buffer layers. This buffer layer is optimised with respect to growth temperature and time for the optical and structural properties of the GaN epilayers. The insertion of a Si x N y intermediate layer significantly increases the optical and structural properties. It results in a reduction of the D 0 X FWHM to 10 meV and in a 2.5-fold increase of its luminescence intensity. The FWHM of symmetric and asymmetric ω-scans are reduced from 832 to 669 arcsec and from 702 to 547 arcsec, respectively.
Heteroepitaxial growth of cubic GaN on Si(001) coated with thin flat SiC by plasma-assisted molecular-beam epitaxy
High-quality cubic GaN films were grown on Si(001) coated with flat ultrathin SiC under different Ga/N flux ratios. The 2.5-nm-thick cubic SiC film proved to be an effective buffer layer for cubic GaN growth on Si(001). Under a Ga-rich condition, films with local atomically flat surfaces were obtained, and the x-ray diffraction full-width at half maximum of (002) peak was 19 min for a 0.82-μm-thick film. The reduced SiC surface roughness decreased the defect density in the GaN epilayers. Under a N-rich condition, the GaN films showed statistical roughening of the surface and a characteristic columnar structure. Under the Ga-rich condition, the columns grew up and then laterally coalesced, so that an atomically flat surface with flat areas in size from 0.05 to 0.40 μm was formed.