Title Page
ABSTRACT
국문 초록
PREFACE
Contents
CHAPTER 1. INTRODUCTION 23
1.1. Introduction of III-nitrides 23
1.1.1. Characteristic of III-nitride 23
1.1.2. History of GaN 31
1.1.3. GaN epitaxial growth by MOCVD 34
1.2. Introduction of GaN-microrod 41
1.2.1. History of GaN based Metal-semiconductor Emitters 41
1.2.2. Internal, Extraction, External, and Power Efficiencies of LED 45
1.2.3. Improved External Quantum Efficiency in GaN-based LED 49
1.2.4. GaN micro & nano structure 54
1.2.5. Growth of GaN microrod 59
1.3. Introduction of hole patterning and PP-PSS 66
1.3.1. Conventional hole patterning 66
1.4. In this study 71
CHAPTER 2. Theoretical background 73
2.1. An early study on the growth morphology of GaN microrod depends on the buffer layer. 73
CHAPTER 3. Experimental 77
3.1. Deterministically-grown GaN microrods on a mask-free plateau patterned substrate 77
3.2. Experimental of selective area growth mechanism 84
CHAPTER 4. Deterministically-grown GaN microrods on a mask-free plateau patterned substrate 88
4.1. Result and discussion 88
4.1.1. Features and advantages of PP-PSS template 88
4.1.2. The mechanism of GaN selective-area growth on PP-PSS 98
4.1.3. Structural morphology of GaN microrods 118
4.2. Conclusion 135
4.2.1. About the 'Deterministically-grown GaN microrods on a mask-free plateau patterned substrate' 135
4.2.2. About the 'Selective-area growth mechanism of GaN microrods on a plateau patterned substrate' 137
4.3. Supplemental information 140
Reference 143
Table 1. Material parameters for III-nitrides and other semiconductors of interest (SiC is considered in its 6H polytype). (a) and (b) correspond to theoretical... 28
Table 2. Comparison of hole patterning methods for general microrod growth. 70
Table 3. Advancing contact angle observed for water and diiodomethane on (I) AlN / sapphire and (II) AlN/SiO₂/sapphire. The RMS of the surface roughness... 108
CHAPTER 1. INTRODUCTION 25
Figure 1.1. Energy bandgap vs lattice constant for selected semiconductors. 25
Figure 1.2. Energy bandgaps and lattice constants for III-N semiconductors with wurtzite (α-phase) and zincblende (β-phase) structures. 26
Figure 1.3. Ball and stick stacking model of crystal (a) with zincblende structure along the [111] direction and (b) with wurtzite structure along the [0001] direction. 27
Figure 1.4. Structure of the (a) Ga-face and (b) N-face GaN. 29
Figure 1.5. Possible chemical reactions and rate limiting steps in MOCVD growth of GaN using ammonia and TMGa. 39
Figure 1.6. Schematic illustration of boundary layer in a horizontal MOCVD reactor. Note temperature and concentration profiles in the boundary layer. 40
Figure 1.7. Quantum efficiency of LED (a) internal quantum efficiency, (b) extraction efficiency, and (c) external quantum efficiency. 48
Figure 1.8. Extraction Quantum efficiency (EQE) of LEDs 52
Figure 1.9. A photo of 2-inch sapphire, i-inch m-plane SiC, and nonpolar/semipolar GaN substrate with a typical size of 5 x 10 mm prepared by... 53
Figure 1.10. Potential of micro & nano LED for high EQE 56
Figure 1.11. Application of micro & nano LED such as XR, AR glass and potential of micro & nano LED 57
Figure 1.12. advantage of micro & nano LED for reduce QCSE 58
Figure 1.13. Two method to fabricate micro & nano LED; Top-down and Bottom-up. 63
Figure 1.14. GaN micro & nanorod growth using MBE, MOCVD using VLS and conventional method. 64
Figure 1.15. Research trends of Bottom-up growth for full-color LED 65
Figure 1.16. General hole patterning methods for microrod growth. 69
Figure 1.17. PP-PSS can compensate for the shortcomings of existing hole patterning. 72
CHAPTER 2. Theoretical background 75
Figure 2.1. GaN epitaxial growth on the PP-PSS depending on buffer layer; low-temperature GaN and AlN buffer layer. 75
Figure 2.2. GaN epitaxial growth on the PP-PSS depending on mask layer; SiO₂ and SiNx layer.[이미지참조] 76
CHAPTER 3. Experimental 80
Figure 3.1. The schematic and information of home-made MOCVD 80
Figure 3.2. The schematic and information of chemical mechanical polishing (CMP) and RF sputtering. 81
Figure 3.3. The information of SiO₂ deposition condition by PECVD and SEM image and information of PSS 82
Figure 3.4. Schematic of the growth process of GaN microrods on a PP-PSS: (a) SiO₂ deposited by plasma-enhanced chemical vapor deposition and (b) chemical mechanical polishing. (c) AlN buffer layer deposited by... 83
Figure 3.5. The method to analysis the PP-PSS using the PP-PSS and indirect samples. 87
CHAPTER 4. Deterministically-grown GaN microrods on a mask-free plateau patterned substrate 91
Figure 4.1. (a) The top and cross-sectional FE-SEM images of a nonpolished PP-PSS and PP-PSS polished for 10, 30, or 60 s. In the cross-section SEM image, the particles under the PSS lens are a piece of sapphire fracture... 91
Figure 4.2. (a) Magnified cross-sectional EDS images of the AlN layer deposited onto the PP-PSS surface. (b) AFM images illustrating the RMS surface roughness values of the AlN layer deposited in the... 94
Figure 4.3. (a) FE-SEM image of initial GaN growth after 1 min of deposition. (b) Schematic of the GaN selective-area growth on the PP-PSS surface; the precursors are diffused on the PP-PSS surface and GaN was... 97
Figure 4.4. (a) A schematic representation of the PP-PSS fabrication process. (b) A schematic illustration and cross-sectional SEM image of GaN growth on the PP-PSS. 100
Figure 4.5. (c) The top and cross-sectional SEM image of GaN growth on the PP-PSS depending on the number of growth cycles. 101
Figure 4.6. Top-view of the SEM image of GaN growth on the PP-PSS in which AlN was deposited according to the material used as the substrate. As the reference on the plateau region, half of the substrate is (a)... 103
Figure 4.7. (a), (b) A schematic representation of the structure of the indirect samples: (I) AlN/sapphire, (II) AlN/SiO₂/sapphire. (c), (d) Surface roughness measurements with two indirect samples using AFM. (e), (f)... 107
Figure 4.8. XRD 2D, 3D pole figure patterns obtained for (a) AlN (002) and (b) AlN (102) from (I) AlN/sapphire, and (c) AlN (002) and (d) AlN (102) from (II) AlN/SiO₂/sapphire. Both samples were heat treated... 111
Figure 4.9. (a) A schematic representation of the plateau region and other regions on the PP-PSS and cross-sectional of low magnification TEM image of the mask layer in the PP-PSS. cross-sectional of high... 114
Figure 4.10. (a) 70° tilted SEM image of PP-PSS, (b) image quality (IQ) map of PP-PSS using backscatter electron (BSE) diffraction, (c) EBSD image of the PP-PSS expressed by overlapping IQ and inverse pole figure... 117
Figure 4.11. (a)-(c) Cross-sectional FE-SEM images of GaN microrods epitaxially grown using 100 cycles of pulsed MOCVD onto the PP-PSS template... 123
Figure 4.12. (a) Low-magnification cross-sectional TEM image of a GaN microrod grown on the PP-PSS surface. (b) High-magnification cross-sectional TEM image of the interface between GaN and the sapphire... 126
Figure 4.13. (c) Selected area electron diffraction (SAED) pattern of sapphire (d) and (e) Fast-Fourier transform images of the AlN intermediate layer and... 127
Figure 4.14. (a) Raman spectra generated over a wide and specific measurement range to characterize the stress in GaN microrods and epilayer. 131
Figure 4.15. (b) Raman spectra generated over a specific range of GaN microrods and the corresponding Gaussian-fitted deconvoluted peaks by Origin. 132
Figure 4.16. PL measured in ranges of 1.6–3.9 eV at 10 K and 300 K for GaN microrods grown on the PP-PSS surface and for the GaN film. 134
Figure 4.17. (a) Schematic of GaN growth mechanism at the slope of PP-PSS lens. (b) Low magnification cross-sectional TEM image of the mask layer in the PP-PSS. (c)-(d) High magnification cross-sectional TEM... 142