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

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Experimental Growth and Characterization Techniques from a two-dimensional net of atoms on the surface, the reciprocal lattice comprises a set of rods perpendicular to the surface in real space. If the Ewald sphere is so large compared to the separation of the reciprocal lattice rods that it will intersect several rods, then it will excite several Bragg reections for any given geometry. Therefore, the diraction pattern therefore comprises a set of streaks indicating 2D crystalline surface as shown in Fig. 4.2(b). The growth rate may be determined from RHEED intensity oscillations, for which the period corresponds to one monolayer of growth. The surface roughness, and therefore the growth mode, may be discerned from the nature of the RHEED pattern. As noted previously, a streaky pattern is an indication of an atomically at surface. In the case of a rough surface, the electron beam will penetrate islands or other structures on the surface, giving rise to diraction from a threedimensional lattice. Therefore, the RHEED pattern becomes spotty in this case as shown in Fig. 4.2(a). The very macroscopic nature of this technique, which lessens its impact in determining exact microscopic structure, is exactly what makes it such a powerful and crucial in-situ tool for the epitaxial crystals grower in determining epitaxial layer quality in real-time during growth 4.2.2 Electron Beam Evaporator system for Silicon Homoepitaxy Another important modication to the Varian Gen II MBE system was the installation of a new electron beam evaporation (EBE) cell from Carrera systems and MBE components for high quality pure silicon homoepitaxial growth. This system consist mainly by three main parts. A high energy electron gun with input voltage up to 10 keV and lament current of 100 mA, and crucible at the middle position dedicated for target loading as shown in Fig. 4.4(b), an electron evaporation controller to control the area and the position of the exposed area of the silicon target, and a deposition sensor equipped with a quartz crystal to measure the growth rate and the thickness of the deposited layer as shown in Fig. 4.3. The process begins under UHV condition of 10 −9 T orr. A tungsten lament inside the electron beam gun is heated. The gun assembly is located outside the 54
4.2 Molecular Beam Epitaxy Technique Figure 4.3: Schematic view of the Si evaporation system with its controlling units and their communication loops. evaporation shown in Fig. 4.4(a) to avoid contamination by evaporants. When the lament become hot enough, it begins to emit electrons. These electrons form a beam which is deected and accelerated toward and focused on the material to be evaporated by means of magnetic or electric elds. When the electron beam strikes the target surface (silicon), the kinetic energy of motion is transformed by the impact into thermal energy (heat). It is important to remember that the energy given o by a single electron is quite small and that the heating is accomplished simply by virtue of the vast number of electrons hitting the evaporant surface. This is the energy which vaporize the target material. The energy level achieved in this manner is quite high, often more than several million watt per square inch (c.f. Fig. 4.4(c)). Due to the intensity of the heat generated by the e-beam, the evaporant holder must be water cooled to prevent it from melting. In the case of conventional silicon MBE, electron beam evaporators (electronguns) are usually used for producing silicon beams, since the vapor pressure of silicon is extremely low, and conventional eusion cells cannot generate sucient 55
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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
Page 18 and 19: Introduction 1.1.2 Thesis Approach
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Page 22 and 23: Theoretical Background of Semicondu
Page 36 and 37: Heteroepitaxial Growth of III-V Sem
Page 64 and 65: Experimental Growth and Characteriz
Page 78 and 79: 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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Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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