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

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Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates Figure 3.3: The fcc crystal structures of dierent semiconductors: (a) The diamond crystal structure. All atoms are of the same type (e.g., Si). (b) The zinc blende crystal structure. The white and black atoms belong to the two dierent sublattices (e.g., Ga and As) [31]. 3.4.1 Dierences in the Crystal Structure The diamond cubic is in the F d3m space group, which follows the face-centered cubic bravais lattice (fcc), where eight atoms are packed and attached at the corners and the centers of each face in the cubic unit cell system. Silicon is one example of diamond structure as shown in Fig. 3.3a. However, a number of semiconductors exhibit the zinc blende (ZB) structure, including GaAs, GaP, InAs and most of III-V semiconductor. It is very similar to the diamond crystal structure, except that the two fcc sublattices are made of two dierent types of atoms. Because of the two types of atoms (c.f. Fig. 3.3b), the zinc blende structure has a lower symmetry than the diamond structure. This can lead to interesting phenomena in the heteroepitaxy of ZB materials on diamond substrates like antiphase domain boundaries and polar/non-polar interfaces [31]. 3.4.2 Large Lattice-Mismatch The major challenging problem during the heteroepitaxial integration is the large lattice mismatch between III-V and Si. Fig. 3.4 summarises the energy gap 32
3.4 Challenges of Heteroepitaxial Growth of III-V on Silicon Figure 3.4: Energy gap versus the lattice constant of the most common III-V semiconductors in comparison to Si. The indirect semiconductor GaP has a lattice constant almost equal to Si, which is very encouraging for almost lattice matched-heteroepitaxy. Figure modied according to reference [41]. plotted versus the lattice constant of the most common III-V semiconductors in comparison to Si. GaAs as well as InP have a lattice constant larger by more than 4% than that of Si. From the values of the lattice constants in Table 3.1 one can calculate the lattice mismatch (f) using Eq. 3.8. Where a S is the lattice constant of the substrate and a L the lattice constant of the grown layer [31]. While GaAs on silicon exhibit a lattice mismatch of 4.1 %, InAs on Si suers by a mismatch of 10.4 %. f = a L − a S a S (3.8) A view at the lattice constants of dierent III-V compound semiconductors plotted in Fig. 3.4 reveals that the indirect semiconductor GaP has a lattice constant almost equal to that of Si with a lattice mismatch about 0.37 %, which is very promising for a dislocation free growth of GaP layers on Si substrates. The mismatch in Eq 3.8 may take on either sign, with some interesting differences observed between the tensile strain, when the lattice constant of the epi-layer is less than the lattice constant of the substrate (f> 0). On the other 33
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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