Improvement of the crystallinity of GaN epitaxial layers grown on porous Si (100) layers by using a two-step method

摘要

A new approach was used for combining GaN and porous Si with the goal of producing high-quality GaN epitaxial layers for optoelectronic integrated circuit devices based on Si substrates. Reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), photoluminescence (PL), and Van der Pauw-Hall effect measurements were performed to investigate the structural, optical, and electrical properties of the GaN epitaxial films grown on porous Si(l00) by plasma-assisted molecular-beam epitaxy with a two-step method. The RHEED patterns were streaky with clear Kikuchi lines, which was direct evidence for layer-by-layer two-dimensional growth of GaN epitaxial layers on porous Si layers. The XRD curves showed that the grown layers were GaN(000l) epitaxial films. The results of the XRD and the PL measurements showed that the crystallinities of the GaN epilayers grown on porous Si by using a two-step growth were remarkably improved because the porous Si layer reduced the strains in the GaN epilayers by sharing them with the Si substrates. Hall-effect measurements showed that the mobility of the GaN active layer was higher than that of the GaN initial layer. These results indicate that high-quality GaN epitaxial films grown on porous Si(100) by using two-step growth hold promise for potential applications in new kinds of optoelectronic monolithic and ultralarge integrated circuits.