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 SiO 2 + 4Ga =⇒ Si + 2Ga 2 O (5.4) SiO 2 + 2Ga =⇒ SiO + Ga 2 O (5.5) The enhancement arises in Fig. 5.3(b),(c) due to additional cleaning of the silicon dioxide from the treated surface according to the chemical processes described in Eq. 5.4 and Eq. 5.5 [83]. Figure 5.3: (1 × 1 µm 2 ) AFM images of 2 MLs InAs QDs grown using SK mode at 420 ◦ C, (a) without Ga treatment, (b) with Ga treatment, and (c) 3D-view of InAs QDs after Ga treatment. This Ga treatment at a temperature of 560 ◦ C for 2 minutes with 15 minutes thermal desorption at 870 ◦ C followed by 2 MLs InAs QDs deposition at 425 ◦ C and V/III ratio of 20 directly on n-doped Si (100) substrate resulted in a strong reduction of the lateral size of InAs QDs from 50 - 70 nm (Fig. 5.3(a)) down to 68
5.3 Results and Discussion 25-32 nm (Fig. 5.3(b),(c)) and a signicant enhancement of the homogeneity of the dot distributions. 5.3.3 InAs Quantum Dots Grown on Silicon Buer Layer The inuence of the growth parameters on the structural properties (size, density and shape) of InAs QDs like In-growth rate, V/III ratio, growth temperature and InAs coverage, were investigated using the following conditions: Ga treatment for 2 min (0.1 ML/s) at 560 ◦ C, thermal desorption at 870 ◦ C for 15 min, 50 nm Si buer grown at 700 ◦ C, 10 min post growth annealing (PGA) at 800 ◦ C on n-doped Si (100) substrate have been performed for all the samples before InAs deposition for additional crystallinity improvement. The growth conditions used here are: V/III ratio 25, growth temperature at 400 ◦ C, Indium (In) growth rate = 108 nm/h, 2 MLs InAs coverage and only one growth parameter was changed (see subsections below). 5.3.3.1 Homoepitaxy of Silicon Buer Layer After in-situ (thermal desorption at 870 ◦ C for 15 min.) and ex-situ (wet etching using buered HF) surface treatment of Si substrate, a silicon buer layer was grown. The electron beam evaporator cell in MBE Gen II was calibrated using two samples. In order to calculate the real growth rate of the (EBE) cell at given emission current I emission and voltage V . Two samples with dierent thicknesses of 50 and 100 nm, respectively were grown according to deposition controller measurements (quartz crystal sensor). However, at the same time the preparation time for each sample was recorded. The real thickness of each sample was measured via prolometer. From thickness measurements, the tooling factor was extracted using Eq. 5.6. T ooling factor = T hickness profilometer(real) × 100 (5.6) T hickness deposition controller This tooling factor value (correction factor) was inserted later in the software of the deposition controller to read the real deposition rate of the silicon cell. The growth parameters which were used for the calibration are; I emission = 72 mA, V 69
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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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Page 32 and 33: Theoretical Background of Semicondu
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Page 36 and 37: 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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