Beam Induced Lateral Epitaxy of GaAs on a GaAs/Si Template
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Beam Induced Lateral Epitaxy of GaAs on a GaAs/Si Template Shigeya Naritsuka1),2), Koji Saitoh1), Toshiyuki Kondo1) and Takahiro Maruyama1),2) 1) Meijo University, Dept. of Materials Science and Engineering, Nagoya, 468-8502 Japan 2) Meijo University, 21st century COE program “NANO FACTORY” ABSTRACT Beam induced lateral epitaxy (BILE) on truncated ridges was applied to the heteroepitaxial growth of GaAs on a Si substrate. A GaAs buffer layer was formed on the Si substrate, and then this GaAs/Si template was used as a substrate for the BILE process. As a result, overgrown regions of GaAs of widths as large as 6.5 µm were grown laterally from the sides of the truncated ridges. The growth regions had a flat, smooth top surface consisting of a (111) facet. Although stacking faults from the GaAs/Si template remained in the growth region, which are unfavorable for device applications, the lateral grown region has no dislocations. Thus, the BILE method is useful for reducing dislocations in heteroepitaxy. INTRODUCTION As microfabrication in Si technology has continued to follow Moore’s law, chip manufacturers now fabricate at the sub-micron scale. However, relatively long delays in the electrical signals occur due to the narrow patterns, and these delays limit the data transmission. It is necessary to overcome this limitation to achieve high performance integrated circuits. Optical communication is capable of fast and high-capacity data transmission. Therefore, optic and electronic techniques are brought together to produce optoelectronic integrated circuits (OEIC), which possess a tremendous power for data processing. To realize OEIC, the technology of heteroepitaxy of high quality GaAs on Si substrates is essential [1-3]. However, these two materials have a large lattice mismatch and a large difference in thermal expansion coefficient, both of which cause a large residual stress in the grown layers, which, in turn, result in a high density of dislocations. Many studies have been done to reduce these problems, but typical growth methods still produce dislocations densities of up to 106 cm-2 [4-6]. Thus, further improvement in crystallinity is needed. Epitaxial lateral overgrowth is an excellent technique for the fabrication of
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high performance electronic and optoelectronic devices because the dislocation density in the overgrown layer can be drastically reduced [7-9]. Recently, we described a new lateral overgrowth technique called beam induced lateral epitaxy (BILE) to achieve a low dislocation density [10]. In BILE, lateral overgrowth is achieved by directing molecular beams at a low angle to a substrate having a truncated ridge structure. Consequently, selective growth can be achieved under a relatively low growth temperature without a SiO2 mask during molecular beam epitaxy (MBE). BILE has a great advantage in this regard because selective growth is generally difficult in MBE because the growth temperature must be kept high to re-evaporate growth species on the mask, which will simultaneously degra
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