Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates stress and strain introduced by mismatched system and crystal defects. The purpose of this chapter is to review the properties and challenges of the epitaxial integration of III-V semiconductors on silicon substrates that bear on these aspects of heteroepitaxy, including crystallographic properties, elastic properties, surface properties as well as the dierent types of structural defects. 3.2 The Concept of Epitaxy The term "epitaxial" is applied to a lm grown on top of the crystalline substrate in ordered fashion that atomic arrangement of the lm accepts crystallographic structure of the substrate. Epitaxial growth is one of the most important techniques to fabricate various "state of the art" electronic and optical devices. Modern devices require very sophisticated structures, which are composed of thin layers with various compositions. Quality, performance and lifetime of these devices are determined by the purity, structural perfection and homogeneity of the epitaxial layers [31]. Epitaxial crystal growth resulting in epitaxial layer perfection, surface atness and interface abruptness depend on a number of factors like: The epitaxial layer growth method, the interfacial energy between substrate and epitaxial lm, as well as the growth parameters - thermodynamic driving force, substrate and layer mist, substrate misorientation, growth temperature, etc. Recently epitaxial growth is used intensively for the fabrication of semiconductor quantum structures like quantum dots giving highly perfect structures with high density. 3.2.1 Fundamental Processes During Epitaxy Regardless of the growth technique, atoms and molecules are delivered to the substrate surface, and a large fraction of these species adsorb on the surface. Once adsorbed, there are three things that can happen to an adatom. It can either form a strong chemical bond to the surface where it is trapped, diuse on the surface to nd an energetically preferred location prior to strong chemical bonding or desorb. Once adsorbed chemically, the adatoms can diuse on the surface and this diusion can be highly anisotropic, depending on the symmetry and nature of 22
3.2 The Concept of Epitaxy Figure 3.1: Schematic diagram of basic possible processes during epitaxial growth. Figure modied according to reference [32]. the surface [32]. These adatoms diuse until they either desorb from the surface, nd another adatom or nucleate to an island, attach or aggregate to an existing island or step, diuse onto the surface or react at a defect site. Diusion onto the surface, or interdiusion can be signicant under certain growth conditions [32]. The main surface process that occur during epitaxy are schematically shown in Fig 3.1 with dierent atomistic processes. The extent of interdiusion can be thought as solubility of one material into other and clearly has strong dependence on the material system. On the other hand, the reactions at defect site are often important. For example, reactions at step edges ( a defect with respect to perfect surface) are the foundation of step-ow growth [31]. The formation of islands and the attachment of atoms to existing structures and clusters are important in the formation of self-assembled (SA) islands (dots). when a diusing adatom nd each other, they can nucleate and form an island. Adatoms that directly impinge to on an island can either incorporate into the island or lead to the next layer growth, depending on the surface potential and energy. As the island continue to grow further, and possibly migrate, they can nd other islands and coalesces into larger islands [32]. 23
Page 1: Molecular Beam Epitaxial Growth of
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Page 16 and 17: Introduction thesis a detailed stud
Page 18 and 19: Introduction 1.1.2 Thesis Approach
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MBE Growth of Self-Assembled InAs a
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MBE Growth of InAs and InGaAs Quant
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Optimization of MEE and MBE growth
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Conclusions substrates, respectivel
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REFERENCES [8] J. M. Gerard, O. Cab
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REFERENCES [29] http://www.wmi.badw
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REFERENCES [49] M. R. Brenner: GaP/
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REFERENCES [66] Y. Ishida, T. Takah
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REFERENCES [84] A. Garcia, C. M. Ma
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REFERENCES [100] M. Felici, P. Gall
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REFERENCES [116] H. Usui, H. Yasuda
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REFERENCES [133] Grassman, T. J. Br
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Conferences Contributions: Tariq Al
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Nomenclature
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REFERENCES symbol Descriptions γ f
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like to thank all member of the Ins
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REFERENCES Erklärung Hiermit versi
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