1. Introduction
          Selective growth is important not only for the fabrication of nanostructures but also for the dislocation reduction in highly lattice-mismatched heteroepitaxy [1]. We have been studying selective growth of GaAs using molecular beam epitaxy (MBE) [2]. However, the window for the selective growth is very narrow because the selective growth is achieved by the re-evaporation of the adatoms on the mask. At the same time, the surface of the epitaxial layer becomes rough because of the high temperature of the growth. The rough surface deteriorates the performance of the devices grown on it. Therefore, a new material for the mask is required to realize selective growth with a smooth surface at low temperature. In this study we focus on graphene as a mask material because it has two-dimensional structure and no bond towards the vertical direction. The critical temperature for the selective growth is investigated with changing the growth temperature. The selectivity is compared with that of a conventional SiO₂ mask.

2. Experimental
          GaAs selective growth was performed by molecular beam epitaxy with using SiO₂ and graphene masks, respectively. Substrate temperature was changed from 580℃ to 600 ℃ to derive a condition for selective growth.While SiO₂ mask was produced by spin-coat method on a GaAs (001) substrate, graphene mask was grown by alcohol chemical vapor deposition (CVD). The grown layers were investigated using a scanning electron microscope (SEM).

3. Results and discussion
          The surface SEM images of selective growth on SiO₂ mask are shown in Fig.1. Although the polycrystal nucleations spread over the whole surface at 580 ℃, the coverage was decreased with increasing the substrate temperature from 590℃ to 600℃. The surface SEM images of selective growth on grapheme mask are shown in Fig.2. Some polycrystal nucleations were found at 580℃, but they almost disappeared above 590℃. The result indicates that the critical temperature of the selective growth on graphene is lower than that on SiO₂, as that on SiO₂ is reported as about 630℃ [2]. The weak bonding characteristics of the graphene is thought to increase the re-evaporation and/or the surface migration of the Ga adatoms. Consequently, the selective growth is able to realize about 30℃ lower on the graphene.

Acknowledgments
          This work was partly supported by Grant-in-Aid for Priority Area (B) No.22360131 from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

Reference
[1] For example, G.Bacchin and T.Nishinaga : J. Crystal Growth 208 (2000) 1-10.
[2] S. Naritsuka, S. Matsuoka, Y. Yamashita, T. Maruyama, J. Crystal Growth, 310 (2008) 1571-1575.

                  (a)                             (b)                           (c)
                       Fig.1 GaAs selective growth on SiO₂

                   (a)                            (b)                            (c)
                     Fig.2 GaAs selective growth on graphene

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/30207 must be provided.

1. Behavior of defects in a-plane GaN films grown by Low-Angle-Incidence Microchannel Epitaxy (LAIMCE)
2. Selective growth of (001) GaAs using patterned graphene mask
3. c-plane GaN selective growth by liquid phase electroepitaxy under atmospheric pressure