臺灣博碩士論文加值系統

本論文研究磷砷化銦鎵磊晶層摻雜稀土元素的光學性質以及介孔矽質MCM-41和MCM-48的發光機制。內容共分成五部分：
(1) 磷砷化銦鎵磊晶層摻雜稀土元素的光學性質：
我們分別使用光激螢光、光電導和無接點電場調制等光譜量測研究摻雜稀土元素磷砷化銦鎵磊晶層的光學性質。在光激螢光光譜中，其峰值的半高寬會隨稀土元素鈥摻雜量增加而明顯變窄。在無接點電場調制光譜中，磷砷化銦鎵訊號的展寬因子也有變窄的現象。從光電導的實驗中，我們利用Urbrach模型去分析吸收尾端的變化，可以得到相關的Urbrach能量值，進而發現Urbrach能量值會隨鈥的摻雜量增加而減少。以上的實驗結果都證實了摻雜稀土元素於磷砷化銦鎵磊晶層中可有效的改善液相磊晶的晶體品質。
(2) 磷砷化銦鎵磊晶層摻雜稀土元素的持續光電導效應：我們對磷砷化銦鎵磊晶層進行持續光電導效應的量測，認為持續光電導的現象是來自樣品中類DX雜質的晶格鬆弛效應。另外，我們也對一系列摻雜鈥元素的磷砷化銦鎵磊晶層進行持續光電導的測量，發現持續光電導的衰減時間和電子捕捉能障都會隨鈥的摻雜量增加而減少。因此我們推論此現象與鈥元素會與樣品中的施子雜質作用有關。
(3)磷砷化銦鎵磊晶層摻雜稀土元素的拉曼散射研究：
我們測量了不同稀土元素含量磷砷化銦鎵磊晶層的拉曼散射，並且利用“空間相關”的模型來分析拉曼訊號的形狀。發現拉曼訊號的不對稱性不會隨稀土元素的摻雜含量而改變。因此，我們認為稀土元素在磊晶過程中有改善磊晶品質的效果，但沒有大量殘留在磊晶層中。
(4) 介孔矽質MCM-41和MCM-48之紅色螢光特性研究：
我們觀察到MCM-41和MCM-48的紅色螢光會包含兩個能量峰值1.9 eV和2.16 eV。這兩個尖峰分別可以歸因於非橋氧電洞中心和與扭曲鍵相關的非橋氧電洞中心。紅色螢光的強度會隨增加快速熱退火處理的溫度而有增強的趨勢，這是因為樣品表面的氫鍵和單一矽氫氧基群相結合而導致非橋氧電洞中心的濃度增加。在激發光源持續激發時，螢光強度會隨時間而衰減，我們認為是超氧分子和樣品表面產生化學鍵結所造成。
(5) 介孔矽質MCM-41之藍綠色螢光特性研究：
我們利用不同的光激螢光技術來研究MCM-41材料在藍綠色螢光的發光機制。由偏振光激螢光和光激螢光激發的結果，可以證實藍綠色螢光的起源來自於樣品表面的二摺疊配位矽中心之三重態至單重態的躍遷。另外，我們提出一個模型來解釋溫度變化的時間鑑別光激螢光實驗。

This thesis studies the optical properties of the rare-earth doped InGaAsP epilayers and mesoporous materials. Different optical techniques such as photoluminescence (PL), photoconductivity (PC), contactless electroreflectance (CER), micro-Raman, polarized PL, PL excitation measurements are carried out to investigate the physical properties of the rare-earth doped InGaAsP epilayers and mesoporous materials. These results are presented in the following parts:
(1) Influence of rare-earth elements doping on the optical properties of quaternary InGaAsP epitaxial layers:
The PL, PC, and CER measurements were used to study the influence of rare-earth doping on the optical properties of InGaAsP layers grown by liquid phase epitaxy (LPE). Both the full width at half maximum (FWHM) of PL and the broadening parameter of CER were found to reduce as the doping amount of Ho element increases. The absorption tails were analyzed with the Urbach tail model and the Urbach energies were obtained from these fits. It is found that the Urbach energy decreases with increasing the doping amount of Ho elements, indicating the Ho doping leads to the decrease of impurity concentrations. The Nd-deoped InGaAsP layers exhibit the similar results and the narrowest value of the FWHM of PL peak is 7.5 meV with Nd of 0.031 wt%. We demonstrate that the introduction of the rare-earth elements can greatly reduce the residual impurities of LPE-grown layers.
(2) Large-lattice-relaxation model for persistent photoconductivity in quaternary InGaAsP epitaxial layers:
We report the first observation of persistent photoconductivity (PPC) in In1-xGaxAsyP1-y epilayers. Under the excitation-energy, temperature, and alloy composition dependence of the PPC effects, it is found that the lattice relaxation of DX-like impurity is responsible for PPC in In1-xGaxAsyP1-y. PPC was also investigated in Ho-doped InGaAsP epilayers with Ho concentrations in the range of 0-0.15 wt%. As the Ho doping increases, the decay-time constant and the electron-capture barrier were found to decrease. We suggest that the introduced Ho elements may chemically react with donor impurities, suppressing lattice relaxation and hence reducing the electron-capture barrier. Also, the rare earth doping is demonstrated to be an effective method of improving the quality of InGaAsP epilayers.
(3) Raman scattering study of rare-earth elements doped InGaAsP epilayers:
Raman scattering measurements have been used to study the structural properties of the rare-earth doped InGaAsP epilayers. Using a spatial correlation model, we found the asymmetric broadening of lineshape of the Raman signal is not influenced by the rare-earth doping. It indicates that no large amounts of the rare-earth elements are being incorporated into the epitaxial layers during the purification.
(4) Red-light emission in MCM-41 and MCM-48 meso-porous nanostructure:
PL was used to study the emission of light from siliceous MCM-41 and MCM-48 that has undergone rapid thermal annealing (RTA). Two PL bands were observed at 1.9 and 2.16 eV and assigned to the non-bridging oxygen hole centers (NBOHCs) and the NBOHCs associated with broken bonds, respectively. The PL intensity is enhanced after RTA. Based on the surface chemistry, the enhancement is explained by the generation of NBOHCs that originates from the hydrogen-bonded and single silanol groups on the MCM-41 and MCM-48 surfaces. The PL intensity degrades with time during photoexcitation. The dominant mechanism of PL degradation involves the formation of the chemisorbed oxygen-related complexes (probably O2－ molecules) on the surface, which are adsorbed onto the surface and act as an efficient quencher of PL.
(5) Blue-green photoluminescence in MCM-41 meso-porous nanotubes:
Different PL techniques have been used to study the blue-green emission from siliceous MCM-41. It is found that the intensity of the blue-green PL is enhanced after RTA. This enhancement is explained by the generation of the two-fold coordinated Si centers and the non-bridge oxygen hole centers according to the surface properties of MCM-41. Through the analysis of PL with RTA, polarized PL, and PL excitation, we suggest that the triplet-to-singlet transition of two-fold coordinated silicon centers is responsible for the blue-green PL in MCM-41. In addition, we suggest a model to explain the temperature dependence of the carrier time constant and the PL intensity.

Abstract (in Chinese) Ⅰ
Abstract (in English) Ⅲ
Acknowledgments Ⅵ
Contents Ⅶ
List of figures X
List of tables XVI
1.Introduction 1
1.1Studies on the optical properties of the rare-earth-doped InGaAsP epilayers 1
1.2Studies on the photoluminescence in mesoporous silica materials 3
1.3References 5
2.Influence of rare-earth doping on the optical properties of quaternary InGaAsP epitaxial layers 8
2.1 Introduction 8
2.2 Background 9
2.2.1 The LPE growth method and In1-xGaxAsyP1-y quaternary alloy 9
2.2.2 Impurity distribution and Band tail 13
2.2.3 Techniques of optical measurement 17
2.3 Experimental details 21
2.4 Results and discussion 26
2.5 Conclusion 35
2.6 References 38
3.Large-lattice-relaxation model for persistent photoconductivity in quaternary InGaAsP epitaxial layers 40
3.1 Introduction 40
3.2 Background 41
The DX center and Large lattice relaxation 41
3.3 Experimental details 44
3.4 Results and discussion 44
3.5 Conclusion 57
3.6 References 58
4.Raman scattering studies of rare-earth elements doped InGaAsP epilayers 60
4.1 Introduction 60
4.2 Background 61
4.2.1 Raman scattering 61
4.2.2 Micro-Raman spectroscopy 63
4.3 Experimental details 65
4.4 Results and discussion 65
4.5 Conclusion 72
4.6 References 73
5.Introduction to mesoporous MCM materials 75
5.1 Basic properties of MCM materials 75
5.2 Synthesis of MCM materials 77
5.3 Applications of MCM materials 79
5.3.1 Catalysts 79
5.3.2 Separation and adsorption processes 80
5.3.3 Molecular host 80
5.3.4 Possible applications in optical devices 81
5.4 References 82
6.Red-light emission in MCM-41 and MCM-48 meso-porous nanostructures 84
6.1 Introduction 84
6.2 Background 86
The defects in silica 86
6.3 Experimental details 88
6.4 Results and discussion 90
6.5 Conclusion 101
6.6 References 103
7.Blue-green photoluminescence in MCM-41 meso-porous nanostructures 106
7.1 Introduction 106
7.2 Background 107
7.2.1 The two fold coordinate silicon centers 107
7.2.2 The optical techniques 107
7.3 Experimental details 109
7.4 Results and discussion 111
7.5 Conclusion 123
7.6 References 125
8. Conclusion 128
9. Publications 131

List of Figures:

Fig. 2.1 Schematic diagram of liquid phase epitaxy (a) Boat construction (b) Furnace arrangement 10
Fig. 2.2 (a) Energy gap of In1-xGaxAsyP1-y versus lattice constant (b) Band structure of In1-xGaxAsyP1-y alloys lattice-matched to InP 12
Fig. 2.3 The Formation of tail of states into the forbidden region, the dashed line show the distribution of states in the unperturbed case 14
Fig. 2.4 Absorption edge of GaAs at room temperature 14
Fig. 2.5 Energy diagram illustrating how absorption probes the conduction band tail of states in a p-type semiconductor 16
Fig. 2.6 Schematic diagram of band-edge photoluminescence processes in semiconductors 18
Fig. 2.7 Optical and photoelectric properties, typical spectral distribution of the optical absorption (curve 1) and photoconductivity (curve 2) 18
Fig. 2.8 The schematic of the sample structure (a) Ho-doped In0.83Ga0.17As0.40P0.60 (b) Nd-doped In0.58Ga0.42As0.9P0.1 23
Fig. 2.9 The experimental system for photoluminescence measurment 24
Fig. 2.10 The experimental system for photoconductivity measurment 24
Fig. 2.11 The experimental system for contactless electroreflectance measurment 25
Fig. 2.12 The 12-K photoluminescence spectra of LPE-grown InGaAsP layers as a function of doping amount of the Ho elements: (a) undoped (b) 0.0166 wt % (c) 0.0253 wt % (d) 0.075 wt % (e) 0.110 wt % (f) 0.1502 wt % 27
Fig. 2.13 The FWHM of the photoluminescence extracted from Fig. 2.12 as a function of the doping amount of the Ho elements. The solid line is guide for the eye 27
Fig. 2.14 The photoconductivity spectra of the Ho-doped sample as a function of the doping amount of the Ho elements: (a) undoped (b) 0.017 wt % (c) 0.025 wt % (d) 0.075 wt % (e) 0.110 wt %. (f) 0.150 wt%. The open circles show the fit to the absorption tail 29
Fig. 2.15 The values of Urbach energy E0 as a function of Ho wt %. The solid line is guide for the eye 31
Fig. 2.16 14-K CER spectra of InGaAsP epilayers as a function of doping amount of the Ho elements: (a) undoped (b) 0.017 wt % (c) 0.075 wt % (d) 0.110 wt % (e) 0.150 wt %. The open circles are fits to a TDFF model for a three-dimensional critical point 31
Fig. 2.17 The FWHM of PL and broadening parameter of CER as a function of doping amount of the Ho elements. The solid lines are guides for the eye 33
Fig. 2.18 (a) 300-K and 13-K PL of undoped InGaAsP epilayers (b) 300-K and 13-K PL of Nd-doped InGaAsP epilayers with Nd of 0.005 wt% 34
Fig. 2.19 The 13-K photoluminescence spectra of InGaAsP epilayers as a function of doping amount of the Nd elements: (a) undoped (b) 0.005 wt % (c) 0.011 wt % (d) 0.031 wt % (e) 0.050 wt % 36
Fig. 2.20 The PL FWHM and intensity of the photoluminescence extracted from Fig. 2.19 as a function of the doping amount of the Nd elements. The solid lines are guide for the eye 36
Fig. 3.1 The LLR model proposed by Lang and coworkers for the properties of the DX center is shown by the configuration-coordinate diagram 43
Fig. 3.2 Decay of PPC in In0.83Ga0.17As0.4P0.6 at temperature T = 14 K. Inset shows excitation energy dependence of PPC decay curves: (a) 1.14 (b) 1.03 (c) 0.95 (d) 0.92 eV 45
Fig. 3.3 PPC decay curves for four representative temperature in In0.83Ga0.17As0.4P0.6. Each decay curve is normalized to a unity at t = 0..48
Fig. 3.4 Replot of Fig. 3.3 as versus . Linear Curves indicate that the PPC decay according to the stretched exponential relation 48
Fig. 3.5 The Arrhenius plot of PPC decay-time constant (τvs 1/T) in (a) In0.83Ga0.17As0.4P0.6 (b) In0.57Ga0.43As0.91P0.09. 49
Fig. 3.6 Decay of 14K-PPC in InGaAsP epilayers with various amounts of Ho doping: (a) 0 (b) 0.025 (c) 0.110 (d) 0.150 wt% 51
Fig. 3.7 Replot of Fig. 3.6 as versus . Linear curves indicate that PPC decays according to the stretched exponential relation 53
Fig. 3.8 Decay-time constant in InGaAsP epilayers as a function of Ho doping at 14K 53
Fig. 3.9 Arrhenius plot of PPC decay-time constant (τvs 1/T) in InGaAsP epilayers with various amounts of Ho doping: (a) 0 (b) 0.025 (c) 0.110 (d) 0.150 wt% 54
Fig. 3.10 Electron-capture barrier in InGaAsP epilayers as a function of Ho doping 56
Fig. 3.11 Configuration coordinate diagram for shallow donor and DX-like impurity centers in InGaAsP. The dashed parabola represents the total energy of DX-like impurity centers when lattice relaxation is reduced 56
Fig. 4.1 Stokes and (b) anti-Stokes light scattering processes (upper panels) in hypothetical three-level system and the corresponding schematic Raman spectra (lower panels) 62
Fig. 4.2 Schematic representation of the micro-Raman experimental apparatus 64
Fig. 4.3 The Raman spectra of In0.83Ga0.17As0.40P0.60 epilayers as a function of doping amount of the Ho elements: (a) undoped (b) 0.017 wt % (c) 0.075 wt % (d) 0.110 wt % (e) 0.150 wt % 68
Fig. 4.4 The Raman spectra of In0.58Ga0.42As0.9P0.1 epilayers as a function of doping amount of the Nd elements: (a) undoped (b) 0.031 wt % (c) 0.050 wt % 71
Fig. 5.1 The schematic of the order array of MCM-41 76
Fig. 5.2 The cubic structure of MCM-48 76
Fig. 5.3 The two mechanisms proposed for the formation of MCM-41: (1) liquid crystal phase initiated and (2) silicate anion initiated 78
Fig. 6.1 Structures of (a) the E’ center (b) the Non-Bridging Oxygen Hole Center (NBOHC) 87
Fig. 6.2 PL spectra of MCM41 and MCM-48 at room temperature. The dashed lines are calculated, fitted Gaussian components 91
Fig. 6.3 PL spectra of (a)MCM-41 and (b) MCM-48 after RTA at room temperature. 93
Fig. 6.4 Possible model structure of (a) the NBOHCs associated with broken bonds (b) hydrogen-bonded NBOHCs. 96
Fig. 6.5 PL degradation of MCM41 and MCM-48 as a function of irradiation time. The inset plots PL degradation as a function of irradiation time, including a dark period (without laser irradiation). 98
Fig. 6.6 PL degradation of MCM-48 as a function of irradiation time in different ambient gases 98
Fig. 6.7 PL degradation of MCM-41 as a function of irradiation time in (a) air, (b) O2 gas. 100
Fig. 6.8 Evolution of PL intensity of MCM-48 as a function of irradiation time in O2 gas. O2 gas was evacuated after 40 minutes 100
Fig. 7.1 Schematic of the photoluminescence excitation (PLE) technique 110
Fig. 7.2 Schematic of the time-resolved photoluminescence (TRPL) technique 110
Fig. 7.3 PL spectrum of as-synthesized MCM-41 nanotubes at room temperature 112
Fig. 7.4 PL spectra of MCM-41 after RTA at room temperature. (a) as-synthesized (b) 200 oC (c) 400 oC (d) 600 oC (e) 800 oC. 112
Fig. 7.5 Polarized PL spectra of MCM-41 nanotubes. Dot and dashed curves correspond to spectra with the polarization of PL parallel and perpendicular to the polarization of the incident beam. Solid curve represents the unpolarized PL spectrum. 116
Fig. 7.6 PLE spectrum of the 2.5-eV emission band from MCM-41 nanotubes.116
Fig. 7.7 The PL decay profiles at (a) 15K, (b) 40K, (c) 100K, and (d) 300K. The open circles show the experimental data and the solid curves are the theoretical fits. 119
Fig. 7.8 Luminescence lifetime of MCM-41 with temperature dependence for the photon energy of 2.5 eV. The solid line is the theoretical curve 119
Fig. 7.9 The Raman spectrum of MCM-41 under excitation by solid-state laser 121
Fig. 7.10 Temperature dependence of the MCM-41 PL spectra. 121
Fig. 7.11 Temperature dependence of the PL intensity at 2.5 eV. The solid line represents the calculated results. 122
Fig. 7.12 Schematic configuration coordinate diagram for absorption and emission processes of MCM-41. 122

List of Tables:

Table 2.1 Values of PL FWHM and Urbach energies of InGaAsP layers with various amount of Ho elements 23
Table 2.2 Values of amplitude, interband transition, broadening parameter, phase, dimensionality in the fitting of CER lineshapes 33
Table 3.1 Decay-time constants and electron-capture barriers as a function of Ho doping 45
Table 4.1 Values of asymmetric ratio of Raman scattering, and correlation length of In0.83Ga0.17As0.40P0.60 layers with various amount of Ho elements. 66
Table 4.2 Values of asymmetric ratio of Raman scattering, and correlation length of In0.58Ga0.42As0.9P0.1 layers with various amount of Nd elements 66

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