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

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MBE Growth of InAs and InGaAs Quantum Dots Embedded in GaAs Matrix related to carrier dynamics in the QDs and have severe inuence on their optical quality [95, 96]. It has been proposed that these structural defects may be circumvented by realization of III/V QDs on the pre-patterned substrates due to the new lattice and strain adjustments of the patterned features [12]. For example, In(Ga)As QDs growth on pre-patterned GaAs substrate is already a well established eld of research due to potential application such as single photon sources and in quantum electrodynamics. For the large scale fabrication of single quantum light sources, tremendous progress in the growth of InGaAs QDs on prepatterned GaAs substrates has been made [97, 98, 99]. Site-controlled InGaAs QDs with very narrow linewidth photoluminescence signal have been achieved both in inverted pyramidal [101, 102] and circular nanoholes [100, 103]. This represents a good motivation to use this approach also for III-V QDs on silicon. 6.2 MBE Growth of SA-InAs Quantum Dots Embedded in Thin GaAs Matrix on Flat Silicon Substrate 6.2.1 GaAs on Silicon Epitaxy The direct epitaxy of GaAs on silicon substrates was subject of research over the last two decades. Recent successful approaches are mainly based on the growth of thick relaxed GaAs buer layer, which is normally composed of two steps growth at two dierent growth temperatures [9, 104, 105]. On the other hand, inserting an intermediate layer between GaAs and silicon like GeSi or short period super lattice (used as strain lter) represent another alternative successful integration of GaAs with silicon [106, 108]. However, our new approach is based on using the islands growth mode of GaAs, at the initial nucleation stage prior to the active layer growth. However, dierent studies have been demonstrated that at the early stages of GaAs-on-Si epitaxy involves no wetting layer [109, 110, 96]; GaAs islands form directly on the substrate and, hence, the initial growth mechanism is Volmer Weber, in which the islanding of the lm occurs because of the energetic favorability of low GaAs coverage (few monolayers) growth on Si . According 104
6.2 MBE Growth of SA-InAs Quantum Dots Embedded in Thin GaAs Matrix on Flat Silicon Substrate to Asai et al. [111], even after the deposition of a GaAs layer with an average thickness of 1 ML to 2 MLs of GaAs onto Si, reections patterns obtained from RHEED conrmed the onset of the islanding mechanism growth. An AFM study revealed the formation on this surface of lens shaped islands at a density of about ∼ 10 11 cm −2 . A further increase in the average thickness of the GaAs layer has little eect on the shapes of the islands, which can be seen in the cross sections of these structures, as it has been presented from dierent research groups [112, 113, 114]. 6.2.2 MBE Epitaxy of InAs/GaAs/Si Structure A misoriented n-type silicon substrate with 5 ◦ o-cut underwent our standard ex-situ (BHF wet etching for 2 min.), and in-situ (thermal oxide desorption at 870 ◦ C for 15 min.) surface treatment. The use of missoriented substrate has been successfully proved that it has signicant inuence on anti-phase domains suppression by means of double-layer step formation [115, 67]. Figure 6.1: (a) Schematic view of the layer scheme of the intended grown structure of (Si/GaAs/InAs/GaAs/Si) (GaAs QDs are in blue color) and (InAs QDs are in yellow color). (b) (1 × 1 µm 2 ) AFM images of 50 nm buer Si grown on 5 ◦ o-cut Si (100) substrate after in-situ and ex-situ surface substrate treatment with RMS value of 0.16 nm. A silicon buer layer with 50 nm thickness was grown directly on 5 ◦ ocut Si (100) substrate at 700 ◦ C followed by 10 minutes post growth annealing 105
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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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Experimental Growth and Characteriz
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Experimental Growth and Characteriz
Page 68 and 69: Experimental Growth and Characteriz
Page 78 and 79: MBE Growth of Self-Assembled InAs a
Page 120 and 121: MBE Growth of InAs and InGaAs Quant
Page 130 and 131: Optimization of MEE and MBE growth
Page 142 and 143: Conclusions substrates, respectivel
Page 144 and 145: REFERENCES [8] J. M. Gerard, O. Cab
Page 146 and 147: REFERENCES [29] http://www.wmi.badw
Page 148 and 149: REFERENCES [49] M. R. Brenner: GaP/
Page 150 and 151: REFERENCES [66] Y. Ishida, T. Takah
Page 152 and 153: REFERENCES [84] A. Garcia, C. M. Ma
Page 154 and 155: REFERENCES [100] M. Felici, P. Gall
Page 156 and 157: REFERENCES [116] H. Usui, H. Yasuda
Page 158 and 159: REFERENCES [133] Grassman, T. J. Br
Page 160 and 161: Conferences Contributions: Tariq Al
Page 162 and 163: Nomenclature
Page 164 and 165: REFERENCES symbol Descriptions γ f
Page 166 and 167: 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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