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

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Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates energy. In other words, mist dislocations are necessarily introduced to release the mismatch strain through defects formation [35]. 3.3 Epitaxial Growth of Lattice-Mismatched Layers The concept of monolithically epitaxial integration of III-V semiconductors on Si substrates is not straightforward and very challenging due to the signicant dierences in basic material and crystal properties that exist between elemental silicon and III-V compounds [14]. In general, when two dierent crystalline materials are brought together by epitaxial mean like in MBE growth, the growth process is called then heteroepitaxy such as the growth of InAs on Si. As a result of the epitaxial integration, a hetero-interface is formed between the III-V materials and silicon in heterostructure junctions [32]. Heteroepitaxy diers from homoepitaxy in that it requires the nucleation of a new phase on a foreign substrate. Because of this, the surface chemistry and physics play important roles in determining the properties of heteroepitaxial deposits, including structural and electrical characteristics, defect densities and structure, and the layer morphology [31]. However, the heteroepitaxy is classied for three main types based on the lattice constants of the two crystalline materials, lattice-matched heteroepitaxy for the same lattice constants and lattice-mismatched heteroepitaxy but elastically strained like InGaAs on GaAs for dierent lattice constants, and partially relaxed as in the case of the growth of InAs on silicon with high mist dislocation density. The heteroepitaxy process is widely used, not only for research but also for manufacturing semiconductor devices such as lasers, light emitting diodes (LEDs) and transistors. 3.4 Challenges of Heteroepitaxial Growth of III-V on Silicon The physical material mismatch issues like lattice and thermal mismatches, and polar on non-polar natures between III-V material and Si undone all previous at- 30
3.4 Challenges of Heteroepitaxial Growth of III-V on Silicon tempts and research activities at defect-free hetero-integration. Lattice constant mismatch in most III-V/Si combinations causes detrimentally high dislocation densities in the III-V epilayers [37]. The thermal expansion coecient dierences between Si and III-V materials leads to variable strain conditions during temperature changes, making alternative large area scale solutions, such as wafer bonding, a signicant challenge [38]. Additionally, the heterovalent (i.e. polar/nonpolar) nature of the III-V/Si interface is a source of numerous harmful defects, such as anti-phase domains (APDs), stacking faults (SF), and microtwins (MT) [1, 39]. The combinations of these problems has proved a signicant road block to high-quality III-V on silicon hetero-integration. In this section, the fundamental challenges and barriers of the epitaxial integration between III-V and silicon are discussed in details. The major material dierences between III-V's like InAs, GaP, GaAs and silicon are summarized in Table 3.1. Semiconductor/Property Si InAs GaAs GaP Crystal structure Diamond Zinc Blende Zinc Blende Zinc Blende Lattice constant (A ◦ ) 5.43095 6.0584 5.6533 5.4512 Thermal expansion coecient 2.6 × 10 −6 5.19 × 10 −6 5.7 × 10 −6 4.7 × 10 −6 at 300 K (K −1 ) Band gap energy at 300 K 1.12 0.354 1.424 2.26 (eV ) Band gap type Indirect Direct Direct Indirect Polarity Non-Polar Polar Polar Polar Table 3.1: Basic material properties dierence between dierent III-V compounds and Si substrate [40]. It can be seen clearly from Table 3.1 that there are signicant disparities in the crystal structure, polarity, lattice constant, thermal expansion coecient and band gap nature between III-V compounds and Si. 31
Page 1: Molecular Beam Epitaxial Growth of
Page 4 and 5: Gutachter (Supervisors): 1. Prof. D
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Page 12 and 13: CONTENTS 3.4.4 Planar Defects Assoc
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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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Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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