Title Page
Contents
ABSTRACT 12
CHAPTER 1. INTRODUCTION 15
1.1. Research Background 15
1.2. Ga₂O₃: Physical properties and Different polymorphs 16
1.3. Homoepitaxial Growth of β-Ga₂O₃ 19
1.4. Issue of Homoepitaxial β-Ga₂O₃ based Power Device 22
1.5. Why α-Gallium Oxide? (α-Ga₂O₃) 25
1.6. Growth Method of α-Ga₂O₃ 27
1.7. Candidate of N-type doping in α-Ga₂O₃ 29
1.8. Previous research of α-Ga₂O₃ Based Power Device 31
1.9. My approach 33
1.10. References 35
CHAPTER 2. Experimental method & equipment 42
2.1. Experimental method 42
2.1.1. Growth of Si-doped α-Ga₂O₃ epilayer 42
2.1.2. Fabrication of Si-doped α-Ga₂O₃ based SBD 44
2.2. Experimental equipment 46
2.2.1. Halide Vapor Phase Epitaxy system 46
2.2.2. Optical Microscopy (OM) 47
2.2.3. Atomic Force Microscopy (AFM) 48
2.2.4. High resolution X-ray diffraction (HR-XRD) 49
2.2.5. Raman spectroscopy 50
2.2.6. Ultraviolet-visible spectroscopy 51
2.2.7. Hall effect measurement 52
2.2.8. Semiconductor analyzer 53
2.2.9. Mask aligner 54
2.2.10. E-beam evaporator (E-beam) 55
2.2.11. Inductively coupled plasma (ICP) etcher 56
2.2.12. Rapid thermal annealing (RTA) 57
CHAPTER 3. Result & Discussion 58
3.1. Growth and Characterization of Si-doped α-Ga₂O₃ on sapphire using HVPE method 58
3.1.1. Surface morphologies of Si-doped α-Ga₂O₃ epilayer 58
3.1.2. Structural properties of Si-doped α-Ga₂O₃ epilayer 60
3.1.3. Transmittance and optical bandgap of Si-doped α-Ga₂O₃ epilayer 63
3.1.4. Electrical properties of Si-doped α-Ga₂O₃ epilayer 65
3.1.5. Double layer n-/n+ of Si-doped a-Ga₂O₃ epilayer for Schottky Barrier Diode 68
3.2. Electrical Characteristics of double layer Si-doped α-Ga₂O₃ based Schottky Barrier Diode 72
3.2.1. Variation of double layer α-Ga₂O₃ samples and SBD 72
3.2.2. The electrical properties of double layer PV-SBD 74
3.2.3. Breakdown voltage measurement 79
3.2.4. Comparison of double layer α-Ga₂O₃ SBD 81
3.3. Conclusion 83
3.4. References 85
RESEARCH ACHIEVEMENTS 88
국문 요약 90
Table 1.1. Characterization of β-Ga₂O₃ and major semiconductor materials for... 18
Table 1.2. Crystal structure and lattice parameter of different Ga₂O₃ polymorphs. 18
Table 1.3. Properties of n-type dopant for grown Ga₂O₃ layer. 30
Table 3.1. FWHM and dislocation density of Si-doped α-Ga₂O₃ epilayer. 62
Table 3.2. Transmittance and optical bandgap of Si-doped α-Ga₂O₃ under... 64
Table 3.3. Contact resistivity and sheet resistance of Si-doped α-Ga₂O₃ 67
Table 3.4. Comparison of double layer α-Ga₂O₃ Schottky Barrier Diode 82
Figure 1.1. Application of Si, GaN, SiC, and Ga₂O₃ high power device market... 17
Figure 1.2. Baliga's figure-of-merit (BFOM) of Ga₂O₃ and major several... 17
Figure 1.3. Conversion relationships of Ga₂O₃ polymorphs with temperature. 18
Figure 1.4. (a) 2inch and (b) 4inch high-quality β-Ga₂O₃ substrates grown by... 20
Figure 1.5. Various growth method of bulk β-Ga₂O₃. 21
Figure 1.6. (a) Table for thermal conductivity of β-Ga₂O₃ and other materials,... 24
Figure 1.7. Previous research of β-Ga₂O₃ on foreign substrate for improving... 24
Figure 1.8. The Unique characteristics of α-Gallium Oxide (α-Ga₂O₃). 26
Figure 1.9. Various growth method of α-Ga₂O₃ thin film. 28
Figure 1.10. The formation energies of Sn and Si under Ga-rich and Ga-poor conditions. 30
Figure 1.11. Influence of Sn background level by memory effect and Hall... 30
Figure 1.12. Previous research of α-Ga₂O₃ based device. 32
Figure 1.13. Schematic images of (a) single layer α-Ga₂O₃ grown according to... 34
Figure 2.1. Schematic image of HVPE system and single layer Si-doped... 43
Figure 2.2. The fabrication process for the α-Ga₂O₃ based Pseudo Vertical... 45
Figure 2.3. Horizontal six zone hot wall home-built Halide Vapor Phase... 46
Figure 2.4. Optical Microscope (OM, Nikon LV-150). 47
Figure 2.5. Atomic force microscopy (AFM, Park Systems, XE-7). 48
Figure 2.6. Triple-axis high resolution X-ray diffraction (HR-XRD,... 49
Figure 2.7. Confocal micro raman system (Nost, FEX). 50
Figure 2.8. UV-vis spectroscopy (Thermo Scientific, Evolutionル 300 UV-Vis Spectrophotometer). 51
Figure 2.9. Hall effect measurement (Lake Shore Cryotronics, 8400 Series HMS). 52
Figure 2.10. Power semiconductor analyzer (KEYSIGHT, B1505A). 53
Figure 2.11. Mask aligner (MIDAS, MDA-400M system). 54
Figure 2.12. E-beam evaporator (E-beam, ULTEC, UEE). 55
Figure 2.13. Inductively coupled plasma ethcer... 56
Figure 2.14. Rapid thermal annealing (RTA, Daedong High Tech). 57
Figure 3.1. (a) Optical microscope (1000x) and (b) Atomic force microscopy... 59
Figure 3.2. (a) 2theta-omega scan profile of Si-doped α-Ga₂O₃ on sapphire... 62
Figure 3.3. (a) Optical transmittance spectra and (b) optical bandgap spectra... 64
Figure 3.4. Cross-sectional and top schematic image of TLM pattern for... 67
Figure 3.5. The ohmic characteristics of α-Ga₂O₃ with different Si flow rate... 67
Figure 3.6. Optical microscope (1000x) and Atomic force microscopy images... 70
Figure 3.7. (a) (0006) and (b) (10-14) plane X-ray rocking curve of double... 71
Figure 3.8. (a) Optical transmittance spectra and (b) optical bandgap calculated... 71
Figure 3.9. Schematic images of (a) double layer α-Ga₂O₃ samples and (b)... 73
Figure 3.10. J-V characteristics of (a) undoped SBD and (b) Si-doped SBD in... 76
Figure 3.11. Specific on-resistance of undoped and Si-doped SBD according to... 76
Figure 3.12. Typical forward J-V characteristics of undoped and Si-doped SBD... 77
Figure 3.13. Calculated ln(J) versus voltage plot of (a) undoped SBD and (b)... 77
Figure 3.14. Schottky barrier height (ФB) for undoped SBD and Si-doped SBD...[이미지참조] 78
Figure 3.15. Breakdown voltage characteristics of (a) undoped SBD and... 80