Kinetic and Strain-Induced Self-Organization of SiGe ...

More documents

Recommendations

Info

26 CHAPTER 2. MOLECULAR BEAM EPITAXY (MBE) 2.3.2 Evaporation and Rate Measurement In this MBE-system electron beam evaporators for silicon, germanium and carbon are used for the deposition of the main epilayer constituents. In the course of this thesis the two formerly small e-beam evaporators for Ge and C were replaced by a larger Ge-source (see Ch. 8). Effusion cells for boron (B, p-type doping) and antimony (Sb, n-type doping) are used and also a carbon sublimation cell is installed. The chamber for special processes is equipped with a C60-effusion cell and can be upgraded and supplied with additional sources, such as for manganese (Mn), in the future. The evaporation rates of the resistively heated effusion cells are temperature controlled. The temperature is measured with tungsten-rhenium thermocouples (Rh 5%/26%) mounted directly below the radiativly heated crucible, and can be stabilized using feed-back loops to adjust the heating currents. Since in this work mainly epilayers consisting of silicon and germanium were grown, in the following the description is restricted to these sources. The schematic principle of an electron beam evaporator is sketched in Fig. 2.8 [12]. A resistively heated hot filament emits thermionic electrons that are accelerated to an energy of 10 keV. This electron beam is de- flected by a static magnetic field following a 270 ◦ arc. The beam strikes the target material which is heated up and evaporated locally. With moderately high power (∼ 1 kW) growth rates of typically ∼ 0.4 ˚A/s for Si and ∼ 0.025 ˚A/s for Ge can be realized. In the case of Si and Ge the evaporation material is located in a crucible of pure silicon that is mounted in a water-cooled copper hearth. A water-cooled roof (stainless steel) that is screened towards the evaporator by Si shields confines the molecular beam. The growth rates are measured using a Sentinel III controller (Leybold Inficon). The measuring principle is based on electron impact emission spectroscopy (EIES). This is an optical technique, where the emission intensities of element-specific atomic transitions that are exited via electron impact, are measured. The signal intensity depends on the density of atoms and therefore on the flux of the evaporated specimen. Growth rates ranging from 0.01 ˚A/s up to 2 ˚A/s can be conveniently measured, but have to be calibrated by the evaluation of thick Si homoepitaxial and SiGe heteroepitaxial epilayers using x-ray diffraction (see Ch. A) and step-height measuring systems (Alpha-Stepper). [12, 53] 2.3.3 Heating and Temperature Measurement Directly above the substrate holder a resistively heated graphite meander serves as thermal radiation source. The substrate is heated by absorbing the radiation emitted from the graphite
2.3. MBE-SYSTEM 27 Figure 2.9: Schematic picture of the Riber SIVA 45 MBE system [12]. � Source: MBE system.jpg heating system. In order to minimize the radial temperature distribution and to improve the temperature homogeneity over the whole wafer a peripherical silicon ring is mounted in between. Two thermocouples are mounted close to the middle of the substrate-backside (one for reserve). These thermocouples have been calibrated against an additional thermocouple that has been cemented into a Si-wafer. To be flexible in measuring the substrate-temperature at any position a pyrometer has been installed. It has been calibrated against the thermocouple and can be used to monitor temperatures in a range between 550 ◦ C to 1050 ◦ C with a measurement spot of about 1 cm 2 . Within this MBE the substrate can be heated up to a temperature of ∼ 1050 ◦ C. The substrate can also be rotated and biased with voltages up to -2000 V during growth. Fig. 2.9 [12] shows schematically the MBE-system used in this work. [12, 53] 2.3.4 Controlling and Monitoring Usually the sources and substrate-temperature are controlled and monitored via PC using the ”EPICAD-software” (Episoft). Using this software process parameters can be changed manually or automatically according to a programmed growth sequence. Several Eurotherm controllers read in the actual values that are provided by the thermocouples and Sentinel sensors. The computer passes the programmed ideal values to the Eurotherm units which calculate the new setpoints and control the sources. The program provides convenient process control and graphical parameter visualization. It provides the possibility of setting calibration functions for temperatures and fluxes and watches vacuum conditions and flow rates of the water-cooling system for an eventually
Page 1: J O H A N N E S K E P L E R U N I V
Page 4 and 5: ii PREFACE Kurzfassung Eine kinetis
Page 6 and 7: iv PREFACE
Page 8 and 9: vi CONTENTS 2.1.3 Growth-Modes . .
Page 10 and 11: viii CONTENTS B General Physical Da
Page 13 and 14: Chapter 1 Silicon-Germanium Materia
Page 15 and 16: 1.1. STRUCTURAL PROPERTIES 5 Figure
Page 17 and 18: 1.2. VICINAL SI(001) 7 Vicinal subs
Page 19 and 20: 1.3. ELECTRONIC PROPERTIES 9 Monoat
Page 21 and 22: 1.3. ELECTRONIC PROPERTIES 11 Silic
Page 23 and 24: 1.4. SILICON GERMANIUM ALLOYS (SI1
Page 25 and 26: Chapter 2 Molecular Beam Epitaxy (M
Page 27 and 28: 2.1. MBE-GROWTH 17 hit the substrat
Page 29 and 30: 2.1. MBE-GROWTH 19 Figure 2.3: The
Page 31 and 32: 2.2. CLEANING PROCEDURE 21 rameter
Page 33 and 34: 2.2. CLEANING PROCEDURE 23 H2SO4 :
Page 35: 2.3. MBE-SYSTEM 25 Figure 2.7: All-
Page 39 and 40: Chapter 3 Methods of Investigation
Page 41 and 42: 3.2. SCANNING ELECTRON MICROSCOPY (
Page 43 and 44: 3.3. ATOMIC FORCE MICROSCOPY (AFM)
Page 51: Part II Main Research 41
Page 54 and 55: 44 CHAPTER 4. SELF-ORGANIZED GROWTH
Page 86 and 87:
76 CHAPTER 5. SELF-ORGANIZED GROWTH
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
86 CHAPTER 6. P-MODULATION DOPING A
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
100 CHAPTER 6. P-MODULATION DOPING
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 125 and 126:
Chapter 7 Transient-Enhanced Si Dif
Page 127 and 128:
7.3. EXPERIMENTAL RESULTS 117 > 100
Page 129 and 130:
7.3. EXPERIMENTAL RESULTS 119 Figur
Page 131 and 132:
7.4. DETAILED CHARACTERIZATION AND
Page 133 and 134:
7.4. DETAILED CHARACTERIZATION AND
Page 135 and 136:
Chapter 8 Germanium Source Reconstr
Page 137 and 138:
Figure 8.2: Elevated front-view of
Page 139 and 140:
water lines. Figure 8.4: Photograph
Page 141 and 142:
Figure 8.7: Part 2 of final constru
Page 143 and 144:
Appendix A Calibration and Characte
Page 145 and 146:
A.1. CALIBRATIONS 135 Figure A.1: X
Page 147 and 148:
A.1. CALIBRATIONS 137 Figure A.3: N
Page 149 and 150:
A.2. PHOTOLUMINESCENCE 139 Sample 1
Page 151 and 152:
A.2. PHOTOLUMINESCENCE 141 Figure A
Page 153 and 154:
A.2. PHOTOLUMINESCENCE 143 Figure A
Page 155 and 156:
Appendix B General Physical Data B.
Page 157 and 158:
Bibliography [1] Herbert Lichtenber
Page 159 and 160:
BIBLIOGRAPHY 149 [42] M. B. Prince,
Page 161 and 162:
BIBLIOGRAPHY 151 [85] J. Zhu, K. Br
Page 163 and 164:
BIBLIOGRAPHY 153 [130] C. S. Peng,
Page 165 and 166:
BIBLIOGRAPHY 155 [174] G. Medeiros-
Page 167 and 168:
BIBLIOGRAPHY 157 [214] G. Bastard,
Page 169 and 170:
Postface Curriculum Vitae ⋄ ∗ 1
Page 171 and 172:
POSTFACE 161 � D. Gruber, D. Pach
Page 173:
POSTFACE 163 Abbreviations AFM Atom
show all

Kinetic and Strain-Induced Self-Organization of SiGe ...

Create successful ePaper yourself

Delete template?

Save as template?