Improvement of the crystallinity of GaN epitaxial layers grown on porous Si (100) layers by using a two-step method
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T.W. Kim Department of Physics, Kwangwoon University 447-1 Wolgye-dong, Nowon-ku, Seoul 139-701, Korea (Received 7 June 2000; accepted 13 July 2000)
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(100) 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(0001) 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.
I. INTRODUCTION
Recently, the optical and the electrical properties of GaN epitaxial layers have been investigated due to their promising applications in optoelectronics devices for the ultraviolet–blue spectral region.1–11 Rapid advancements in epitaxial layer growth technologies have made possible the growth of high-quality GaN epitaxial layers on (0001) sapphire substrates. Although many works concerning the growth of the GaN epilayer have been reported, almost all of the substrates used were sapphire substrates. The new idea of combining GaN with Si materials is attractive due to the great potential for using Si as a low-cost, very large-area substrate in optoelectronic devices. Even though some works concerning the structural and the optical properties of GaN epitaxial layers on 3C–SiC-coated Si(100) and Si(100) substrates have been reported,12,13 to the best of our knowledge, the structural, the optical, and the electrical properties of GaN epitaxial layers grown on porous Si layers by using a two-step growth method have not yet been investigated. Since the stress due to the differences in the lattice constants and in the thermal expansion coefficients between GaN and Si 2602
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J. Mater. Res., Vol. 15, No. 12, Dec 2000 Downloaded: 24 Mar 2015
can probably be relaxed by using a porous Si layer, highquality GaN epitaxial layers can be achieved on porous Si layers.14,15 This paper reports structural, optical and electrical data for GaN epitaxial layers gr
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