Selective Growth of GaAs on GaAs-Coated Si Substrate by Liquid Phase Electro-Epitaxy
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SELECTIVE GROWTH OF GaAs on GaAs-COATED Si SUBSTRATE BY LIQUID PHASE ELECTRO-EPITAXY Shiro Sakai and Yasuno Ohashi. Department of Electric and Electronic Engineering, Tokushima University, minami-josanjima, Tolkshima 770, Japan ABSTRACT The selective LPEE (liquid phase electro-epitaxy) growth of GaAs on GaAscoated Si substrate prepared by MOCVD has been performed. Several attempts, the use of the insulator melt cap, lowering of the melt height and optimization of the stripe direction, have been tried to increase the lateral growth rate. Very wide (60 pm) lateral overgrowth on the SiO 2 mask is obtained by making the stripe window in and equivalent directions and by increasing the lateral current component in the LPEE. The GaAs layer laterally grown on the SiO 2 has much less EPD (etch pit density) showing that the defect in the MOCVD-GaAs is blocked by the SiO 2. The growth mechanism and the method of increasing the lateral growth rate are discussed. Introduction The selective lateral growth of GaAs on GaAs-coated Si substrate is one of the promising ways to improve the film quality of GaAs grown on Si substrate [1]. The hybrid growth which is performed as follows is adapted to obtain the lateral growth. First, the GaAs layer is grown on Si substrate by MOCVD (metalorganic chemical vapor deposition) or by MBE (molecular beam epitaxy), and then the grown surface is covered by the SiO 2 or SiN except for the small area which acts as a seed for growing GaAs on SiO 2 in the lateral direction. The dislocation generated at GaAs/Si interface is blocked by the Si0 2 mask and no longer propagates in the laterally grown layer as schematically shown in Fig. 1. LPE(liquid phase epitaxy) is used as a second growth method, because it gives large lateral growth rate. This hybrid growth technique was first applied in growing GaAs on Si by Sakai, et al [1], and later by Ujiie and Nishinaga [21 who could obtain lateral overgrowth on the SiO 2 mask using (111) Si substrate. The lateral growth rate, however, was found to be very small if (100) Si substrate was used. One of the reasons for this slow lateral growth rate is due to • LPEE-GaAs the growth mechanism [3]. V-MOCVD-GaAs The growth nucleates at the dislocation existing in the Si substrate MOCVD-GaAs on Si making the growth mechanism transportFig. 1 The structure fabricated by LPEE Mat. Res. Soc. Symp. Proc. Vol. 237. 01992 Materials Research Society
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limited,
while it is surface reaction ratelimited in the growth on low-dislocation densityGaAs substrate. To enhance the lateral growth on the mask, we have applied LPEE (liquid phase electroepitaxy) in which the
rv=l
U+Ator)
LT
....
CURRENT
Poo PBN
current flows from the
substrate to the melt in the conventional temperature-controlled
LPE [4]. The growing
Si SUBSTRATE
CARBON
species arriving on the Fig.2 Melt and substrate holders SiO 2 surface is drawn into the window region by the electro-migration. The lateral growth rate reported in the previous paper, however, was not long, and the aspect ratio defined by t
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