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

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Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates Figure 3.11: HR-TEM image of stacking faults defects loops found in Si/InAs/Si system. TEM performed@PDI-Berlin. planes, which lies along a [110] direction parallel to the interface [66]. Annihilation reactions can also occur between APDs on [011] planes [31], which can meet along a [010] direction, as shown in Fig. 3.10. The high single density aorded by substrate misorientation decreases the spacing between neighboring APDs, hence increasing the probability that neighboring APDs will nd one another and form small close domains. Many reports of single domain GaAs/Si and GaAs/Ge in the literature actually refer to initial two domain III-V growth, followed by rapid annihilation of APDs near the interface, leaving a single dominant domain [67, 68, 69]. In the limit of vicinal (001) substrates, however, the spacing between adjacent APDs is thought to be quite large such that self annihilation near the interface of single-domain becomes less likely [50]. 3.4.4.2 Stacking Faults Stacking faults (SFs) are produced when the regular arrangements of layer atoms are disturbed. A perfect crystal can be considered a stack of atomic layers occurring in a particular sequence. The stacking of the zinc blende structure of III-V semiconductor in the [111] direction can be described as ABCABC. A stacking fault can occur with an extra plane of atoms inserted into the stacking sequence, as in ABCBABC, a B layer is inserted. This is called an extrinsic stacking fault. 46
3.4 Challenges of Heteroepitaxial Growth of III-V on Silicon Figure 3.12: HRTEM image of micro twin and stacking faults defects (S1,S2) in GaP/Si system. Figure modied according to reference [70]. Another possible type of stacking fault involves the removal of one plane, as in ABCBC, an A layer is removed and is called an intrinsic stacking fault [31]. Stacking faults are planar defects that are bounded on either side by partial dislocations. Fig. 3.11 shows a high resolution transmission electron microscopy image of SFs defects and SF loops found in InAs QDs embedded in Si matrix system, grown in our MBE system and characterized at Paul Drude Institute (PDI)- Berlin. It was also reported for GaP/Si system that initial planar nucleation of GaP/Si is dicult to control, often creating many small faceted GaP islands. Coalescence of these GaP islands often results in the formation of SFs, which then propagate throughout the entire GaP layer [70]. Later reports indicted that SFs could be suppressed by forcing a 2D growth mode for the rst few layers of GaP using migration enhanced epitaxy (MEE) for the nucleation process on Si substrate. Thus, it is essential to carefully monitor polar/non-polar of III-V/Si interface and ensure a low density of SFs [39]. 3.4.4.3 Micro Twins Another type of planar defect resulting from a change in the stacking sequence are the micro twins (MTs). In diamond and zinc blende crystals, twinning occurs almost exclusively on [111] planes. Using the stacking notation used in the last section (Sec. 3.4.4.2), a twin boundary in a diamond or zinc blende crystal may 47
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Molecular Beam Epitaxial Growth of
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Gutachter (Supervisors): 1. Prof. D
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patterns indicating a 2D smooth sur
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(MEE = migration enhance epitaxy) u
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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
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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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