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 Sample Number Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Growth Conditions 50 nm Si at 700 ◦ C + PGA at 800 ◦ C for 10 min. + 2 ML InAs QDs at 400 ◦ C 50 nm Si at 700 ◦ C + PGA at 800 ◦ C for 10 min. + 2 ML InAs QDs at 400 ◦ C + 10 nm Si at 400 ◦ C 50 nm Si at 700 ◦ C + PGA at 800 ◦ C for 10 min. + 2 ML InAs QDs at 400 ◦ C + 10 nm Si at 400 ◦ C+ PGA at 700 ◦ C for 5 min. 50 nm Si at 700 ◦ C + PGA at 800 ◦ C for 10 min. + 2 ML InAs QDs at 400 ◦ C + 10 nm Si at 400 ◦ C+ PGA at 700 ◦ C for 5 min.+ 40 nm Si at 700 ◦ C 50 nm Si at 700 ◦ C + PGA at 800 ◦ C for 10 min. + 2 ML InAs QDs at 400 ◦ C + 10 nm Si at 400 ◦ C+ PGA at 700 ◦ C for 5 min.+ 40 nm Si at 700 ◦ C+ PGA at 800 ◦ C for 5 min. Table 5.2: capping investigations. The samples series with detailed growth conditions for the PGA and Si 5.4.3 The Inuence of Post-Growth Annealing and Si Capping In order to study the eect of post growth annealing (PGA) and Si overgrowth (capping) on the grown structure, another series of samples were prepared for this study. Table 5.2 summarized the growth conditions of the grown samples investigated in this section. An interesting Si surface reconstruction and evolution around and over the InAs QDs were observed. In addition, InAs QDs experienced a shape transition from at and pyramidal shape to spherical and multi-faceted QDs shape after PGA and further Si capping. These series of samples were grown on exactly oriented Si (100) n-doped substrates. After our standard in-situ and ex-situ surface treatment, a 50 nm silicon buer was grown at 700 ◦ C followed by 10 minutes PGA at 800 ◦ C. Afterwards, the substrate temperature was reduced to 400 ◦ C for further 2 MLs deposition of InAs QDs. The rst sample was unloaded directly after 2 MLs InAs QDs growth for 80
5.4 Self-Assembled InAs QDs Embedded in Si Matrix structural characterizations. Fig. 5.14(a) shows the AFM image of such a QD sample grown on a Si buer layer. The size distribution of dots ranges in diameter D = 15 - 30 nm and in height h = 5 - 15 nm, respectively, which is consistent with TEM measurements. Figure 5.14: The structural properties of 2 MLs InAs QDs grown on 50 nm Si buer. (a) (1 × 1 µm 2 ) AFM image of 2 MLs InAs QDs growth using SK mode. (b) HR-TEM image of a single InAs QD (D =20 nm, H = 9 nm) with an inhomogeneous wetting layer pointed in red arrow and 2 MLs coherent layer above the wetting layer of distorted InAs QD in zoomed area (dashed yellow color). (TEM performed@PDI-Berlin) [86]. A HR-TEM image of a typical single InAs QD is shown in Fig 5.14(b). The HR-TEM image with zoomed area (yellow dashed area) shown in the inset of Fig 5.14(b) conrmed the existence of an inhomogeneous wetting layer marked with a red arrow with an interesting InAs/Si interface. Directly after the highquality Si buer layer shown in Fig 5.14(b), a 2 MLs thick InAs coherent layer was detected. The defects start after this coherent layer with high tetragonal distortion in lattice constant. From the last observations, one can conclude that the detected inhomogeneous wetting layer is an evidence, which conrms the formation of InAs QDs under the described growth conditions (sample 1 Table 5.2) follows the SK-mode during the initial QDs nucleation stage with half lens to pyramidal QDs shape in most of the cases. However, the same growth steps in Sec. 5.4.3 were used to prepare the second sample, but this time with further 10 nm cap layer deposition at the same growth temperature of InAs QDs (400 ◦ C). 81
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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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viii
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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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Page 44 and 45: Heteroepitaxial Growth of III-V Sem
Page 64 and 65: Experimental Growth and Characteriz
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Page 130 and 131: Optimization of MEE and MBE growth
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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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