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

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MBE Growth of Self-Assembled InAs and InGaAs Quantum Dots Embedded in Silicon Matrix followed by dry and wet etching possibly cause serious crystalline damages and some external chemical impurities [16]. 5.4.1 Experimental Details Self-assembled (SA) InAs quantum dots (QDs) were grown in silicon matrix with dierent nominal thicknesses and on dierent substrate o-cuts. The rst series of samples were grown on exactly oriented (100) n-type, phosphor doped silicon substrate, while the second series were grown on 5 ◦ o-cut n-type (100) Si substrate. After our standard ex-situ (2 min. BHF wet etching) and in-situ thermal oxide desorption at 900 ◦ C for 15 minutes, silicon buer layer with a 50 nm thickness was grown at 700 ◦ C followed by 10 minutes post growth annealing (PGA) at 800 ◦ C, in order to improve the crystallinity of the silicon buer. Figure 5.10: Schematic diagram of X (1, 2 or 4) MLs InAs QDs embedded in Si matrix. (a) Energy scheme of the structure. (b) Layer scheme of the grown structure. The substrate temperature reduced after that to 400 ◦ C. At this temperature two samples were grown with 1 ML, 2 MLs or 4 MLs InAs QDs (see Fig. 5.10). At 400 ◦ C another 10 nm silicon cap layer was deposited to protect the InAs QDs from desorption. The substrate temperature was ramped up to 700 ◦ C with a 76
5.4 Self-Assembled InAs QDs Embedded in Si Matrix ramping rate of 50 K/min for the growth of further 40 nm of Si to form nally a 50 nm thick cap layer in two growth steps. At the nal stage, another 10 minutes PGA was performed to improve the crystallinity of the whole structure. Fig. 5.10(a) shows the band structure scheme of the intended grown structure (Si/InAs/Si/InAs), while Fig. 5.10(b) shows the layer scheme of the same structure. The top InAs QDs layer was grown for AFM characterization and the sandwiched (buried) InAs layer for PL characterization. The growth conditions of SA InAs QDs used for the preparation of the two series are: V/III = 25, T G = 400 ◦ C, In growth rate = 108 nm/h (0.1 ML/s) with dierent nominal thickness of 1, 2 or 4 MLs InAs QDs. Figure 5.11: (1 × 1 µm 2 ) AFM images of InAs QDs top layer on exactly oriented Si (100) (rst series structure). (a) 1 ML InAs coverage , (b) 2 MLs InAs nominal thickness. 5.4.2 TEM Characterization of Si/InAs/Si Structure The samples in Fig. 5.11 were optically characterized by a macro PL setup and did not show so far any optical activity. The possibility of obtaining coherent InAs QDs embedded in Si matrix needs extensive studies. Therefore, intensive TEM studies of the internal structure and interface quality were preformed at the Paul Drude Institute (PDI) - Berlin. TEM investigations can give a deep understanding of the growth scenario (structure evolution), strain analysis, and defects types, which could in turns identify the possible reasons behind the irradiative recombinations in the grown structure. The stacking faults density was 77
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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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CONTENTS 3.4.4 Planar Defects Assoc
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CONTENTS xii
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Introduction thesis a detailed stud
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Introduction 1.1.2 Thesis Approach
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Introduction 1.2 Thesis Outline The
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Theoretical Background of Semicondu
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Heteroepitaxial Growth of III-V Sem
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Heteroepitaxial Growth of III-V Sem
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Page 130 and 131: Optimization of MEE and MBE growth
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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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