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Selective growth of (001) GaAs with graphene mask

Yujirou Hirota ,  Yuya Shirai ,  Hiromu Iha ,  Yusuke Kito ,  Manabu Suzuki ,  Hironao Kato ,  Nao Yamamoto ,  Takahiro Maruyama ,  Shigeya Naritsuka 

Department of Materials Science and Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan

Abstract

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

 

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Related papers

Presentation: Poster at 15th Summer School on Crystal Growth - ISSCG-15, by Yujirou Hirota
See On-line Journal of 15th Summer School on Crystal Growth - ISSCG-15

Submitted: 2013-06-13 14:24
Revised:   2013-06-13 14:25