A selective growth of GaAs microcrystals grown on Se-terminated GaAlAs surface for the quantum well box structure
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A selective growth of GaAs microcrystals grown on Se-terminated GaALAs surface for the quantum well box structure Toyohiro Chikyow and Nobuyuki Koguchi
National Research Institute for Metals,Tsukuba Laboratories, 1-2-1 Sengen Tsukuba-shi Ibaraki 305 Japan
ABSTRACT Aselective growth of GaAs microcrystals was demonstrated on a Se-terminated GaAIAs surface. Ga molecules were supplied to the Se-terminated GaAIAs surface at first. The surface consisted of Ga droplets and bared Se-terminated GaAIAs surface. After the following As molecule supply to the surface, a selective GaAs microcrystal growth from Ga droplets was observed. The cross sectional investigations by the high resolution electron microscope revealed epitaxial growth of GaAs microcrystals with (111) facets and a possibility of (GaAI) 2Se. layer formation at the GaAs/Se-terminated GaAIAs interface.
INTRODUCTION Recent advances in micro fabrication techniques in semiconductor enabled the realization of fine structures where carriers are confined in low dimensions[1]. A structure with the carrier confinement in quasi-zero dimension is defined as "the quantum well box". The quantum well box has been expected as a leading candidate for an advanced semiconductor laser with a fine coherency and a low threshold current density[2]. In fabricating the quantum well box, an uniform size fine structure without defects or damages must be required[2]. In addition, for the quantum size effect observation, the size of the quantum well box must be smaller than 100 nm in diameter of the inscribed sphere of the structure[3]. For this purpose, the Droplet Epitaxy, a method of a crystal growth from Ga or In droplets, has been proposed[4-8]. From our previous reports where a selective growth of GaAs microcrystals was demonstrated on a ZnSe surface by the Droplet Epitaxy[4,5], the essential factors were found that 1) a surface does not react with Ga atoms, that 2) the surface gives no sites for As molecule adhesion and that 3) the substrate surface has a similar atomic configuration to that of GaAs surface for the epitaxial growth. If another surface would satisfy the required conditions, microcrystal growth of GaAs from Ga droplets would be expected. Recently a sulfur terminated GaAs surface has been focused as a surface passivation method due to its chemical stability[9,10]. From these reports, group VI elements terminations, such as S or Se termination, seem to satisfy the required conditions for our method because the terminated surface will not give proper sites for reaction with Ga and As molecules. The sulfur molecules, however, is not easy to handle due to the high vapor pressure. Se molecules as another candidate seem to be preferable compared with S molecules. In this paper, it is investigated whether the Se-terminated GaAIAs surface is available as the substrate for the microcrystal growth from Ga droplets. At the same time, a structure of GaAs/Seterminated GaAIAs is investigated by a high resolution transmission electron microscope (HRTEM) combined with a lattice ima
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