The study aims at growing nonpolar GaN film on LiGaO2 substrate by chemical vapor deposition (CVD). Metallic gallium and NH3 are the sources of Ga and N. There are two sets of experiment: add NH3 when raising the temperature, and set different reacting pressure at each experiment; add N2 when raising the temperature, and set different reacting temperature at each experiment, while reach the reacting temperature add NH3. Analyze the reacted samples with X-ray diffraction, scanning electron microscope, electron back-scattered diffraction, atomic force microscope and transmission electron microscopy to know the growing direction, morphology, roughness, optical property, and the microstructure of GaN growing situation. Under the experimental conditions, add NH3 when raising the temperature and set the reacting pressure in the range of 50 torr ~ 400 torr at 950¢XC with NH3 flow rate 450sccm for 60 minutes, m-plane GaN can be obtained; setting different reacting temperature(900¢XC ~ 1000¢XC) at 50 torr with N2/NH3 flow rate 450/30sccm for 60 minutes can also get m-plane GaN. Besides, the thin film of pure m-plane GaN can be obtained when setting the reacting temperature at 1000¢XC, but the film peels off seriously. After reacting under the conditions of the first set experiments, the inside LGO substrate become damaged, pores can be observed easily; and the circumstances of LGO is better in second set experiment.

In this thesis, we investigated the growth of nonpolar (11-20) GaN films on LiGaO2 substrate by a simple chemical vapor deposition (CVD) process. Metallic gallium, NH3 and ultra-purity nitrogen were used as Ga, N sources and carrier gas. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to study the influence of growth conditions such as reaction pressure, growth temperature and deposition time on the GaN epilayer¡¦s orientation and surface morphology. It¡¦s found that GaN epilayers have different surface morphology grown on LiGaO2 substrates by the change of growth pressures (50 torr ~ 400 torr) under temperature of 950 ¢XC, NH3 gas flow of 450 sccm and the growth time of 60 minutes, and uniform a-plane GaN epilayers are found with growth pressures 50, 200 and 300 torr. In addition, we obtain uniform a-plane GaN epilayers with different surface morphology by the change of growth temperatures (900 ¢XC ~ 975 ¢XC) under pressure of 50 torr, N2/NH3 gas flow of 450/30 sccm and the growth time of 60 minutes. Furthermore, we obtain flatter a-plane GaN epilayer by a longer growth time (120 mins) under temperature of 950 ¢XC, pressure of 50 torr and N2/NH3 gas flow of 450/30 sccm. The orientation relationship between GaN and LiGaO2 was determined as (11-20)GaN // (010)LiGaO2 and (1-100)GaN // (100)LiGaO2 by TEM analysis.

¡@¡@In this thesis, the formation of m-plane (10-10) Gallium nitride (GaN) on the surface of a-plane (100) lithium gallate (LiGaO2, LGO) substrates via nitridation with ammonia (NH3) at high temperature. The parameters in this research were mainly focus on temperature, ammonia flow rate, reaction pressure, and growth time. ¡@¡@Specimens were analyzed with various instruments. X-ray Diffraction patterns showed that the nitridation process on LGO substrate resulted in the formation of the GaN single crystalline films. The crystalline quality of the GaN film could be improved by changing parameters of nitridation process. Scanning electron microscope image showed that the structure of GaN films was nanoporous. A red shift in the E2(high) phonon peak of GaN from micro-Raman indicates a compressive stress in the porous GaN with respect to the single crystalline epitaxial GaN. PL intensity ratio (INBE/IYL) of the porous GaN was found to be increased as changing parameters of nitridation process, namely the optical and crystalline quality of porous GaN was improved. Hall measurement showed that the porous GaN was p-type, and it had high hole concentration, good mobility, and low resistivity. Analyses of the elements depth profile by Auger electron spectroscopy. Transmission electron microscopy was used to observe the high resolution cross-section of porous GaN. From the selected area electron diffraction patterns, the orientation relationship between porous and LGO was determined as [100]LGO//[10-10]GaN and [0-10]LGO//[11-20]GaN when zone axis was [0001].

This article aims at growing (0002) InN film on LiGaO2 substrate by chemical vapor deposition (CVD). High purity InCl3 and metallic indium were used to react with NH3 respectively to form InN. Different experimental condictions such as growth temperature and the reaction pressure were adopted and compared to grow a well crystalline structure and smooth InN thin film. After one hour reaction, InN deposits on LiGaO2 substrate. X-ray diffraction, scanning electron microscope, atomic force microscope, photoluminescence, and transmission electron microscope of the samples were measured to investigate the crystal orientation, crystal quality, surface morphology, and microstructure. Based on the result, we can get the best condiction to grow the InN thin film. Through the experimental results, it is found that InN can not be successfully grown by using metallic indium. Oppositely, it is not difficulty to form InN by using InCl3. After a series of attempts on experiments, the temperature of 600 ¢J and the pressure of 400 torr are found to be the best condiction to grow the InN thin films.

In the thesis, epitaxial ZnO films were grown by chemical vapor deposition method (CVD) on LiGaO2 (001) substrate. Zinc 2,4-pentanedionate monohydrate [Zn (C5H7O2) 2. H2O] , used as the zinc precursor, was vaporized at the temperature between 130 to 140¢J. Then the vapor was carried by a mixture of N2/O2 gas flow into the furnace where the (001) LGO substrate located. The parameters of growth temperature, growth pressure and growth time were adjusted to found the best ZnO films growth conditions. After CVD growth, the crystal structure, crystal quality, surface morphology, optical properties, surface roughness and micro-structure properties of the specimens were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), atomic force microscopy (AFM) and transmission electron microscopy (TEM). This study was divided into three parts. In the first parts, the dependence of growth characteristics on the different growth temperatures was investigated. The best surface morphology and crystal quality of ZnO films were grown under the growth temperature of 550 ¢J. In the second parts, the growth of ZnO films under various pressures was investigated. High orientation (0002)ZnO films were grown at lower growth pressure of 50 torr. In the third parts, the dependence of growth time on the ZnO films quality was investigated under growth temperature of 550 ¢Jand growth pressure of 50 torr.

The powder phosphor of £]-LiGaO2¡GCe3+ ¡B£]-LiGaO2¡GEu3+ and £^-LiAlO2 were prepared by using the reagents of Ga2O3 (99.999%), Al2O3 (99.99¢H), Li2CO3 (99.999%), CeO2 (99.98%) and Eu2O3 (99.98%). Cerium and europium doped £]-LiGaO2 respectively and europium doped £^-LiAlO2 phosphors were synthesized by the method of high temperature solid-state reaction. The Ga, Al, Li, Ce and Eu reagents were mixed according to the requisite stoichiometric ratios. The mixture was mixed thoroughly and sintered at requisite temperature in a tube furnace in atmosphere for several hours. Then the products were cooled down to room temperature and ground into powder to get the final product. The phase purity and crystallinity of the as-synthesized, cerium and europium doped £]-LiGaO2 phosphors respectively and europium doped £^-LiAlO2 phosphors, were characterized using x-ray powder diffraction. The particle size and the morphology of the samples were analyzed by scanning electron microscopy. Luminescence properties of the £]-LiGaO2 and the £^-LiAlO2 phosphor samples with different cerium doping and europium doping concentrations were studied. The photoluminescence spectra of cerium doped £]-LiGaO2 showed a broad yellow-green light emission range from 450 to 640 nm with the peak at 519 nm. The strongest intensity peak of luminescence was found at 0.5 % cerium doping concentration synthesized at 1000¢J. The photoluminescence spectra of europium doped £]-LiGaO2 and £^-LiAlO2 showed the orange-red light emission range from 588 to 630 nm with the maximum peak at 612 nm. The strongest intensity peaks of luminescence were found respectively at 9 % and 7 % europium doping concentration synthesized at 1000¢J.

¡@In this thesis, we have studied the growth of M-plane GaN thin film on LiGaO2 (100) substrate by Plasma-Assisted Molecular Beam Epitaxy. We found that the growth of GaN thin films on as-received LiGaO2 substrates is poly-crystalline by analysis of X-ray diffraction, and these of GaN thin films were peeled off after thin film process. Using atomic force microscopy (AFM) to scan the surface of as-received LiGaO2 substrate, we found that many particles which are Ga2O3 existed on the surface of as-received LiGaO2. The annealing ambient for LiGaO2 substrates in vacuum and air ambient has been studied in order to improve the surface of LiGaO2. The scanning results of AFM shows that the crystal quality and stress of M-plane GaN grown on LiGaO2 (100) substrate pre-annealed in air ambient is significantly improved. We conclude that the reason of GaN peeling off from LiGaO2 substrate is attributed to stress between GaN/ LiGaO2. The measurement of polarization-dependent PL shows that the luminescence intensity of growing sample increases and reaches a maximum at £p = 90¢X (E¡æc), which indicates the growing samples is M-plane GaN as well. The microstructure of growing samples was characterized by transmission electron microscopy. We found that the formation of stacking fault in GaN is attributed to the growth of GaN on cubic-Ga2O3 nano-particles. The formation of Ga2O3 nano-particles can be suppressed by pre-annealing LiGaO2 substrate in air. It revealed that the thermal annealing LiGaO2 substrate in air ambient can improve the surface of LiGaO2 substrate effectively, and then one can grow a high quality M-plane GaN thin film on the LiGaO2 substrate.

No description available.

In this paper, polar free-standing (0002)GaN wafer were fabricated by using the hydride vapor phase epitaxy(HVPE) technique on (002) LiGaO2 substrates. Polar of The (0002) GaN affects its luminous efficiency, but compared to other surface between the substrate, it has the smallest lattice mismatch. With the high growth rate of HVPE, hoping to grow high quality GaN thick layer. In the self-designed reactor, Metallic gallium and NH3 were the source of Ga and N. Nitrogen and hydrogen were used as the carrier gases HCl and nitrogen was designed to pass through liquid Ga to form GaCl fully. GaN deposition was realized Efficaciously by conducted steady NH3 and GaCl flows to the substrate suface, accommodated with additional hydrogen and nitrogen atmosphere flows.The parameters set of research mainly focus on reaction pressure, temperature, and growth time. In order to obtain better crystal quality, more attempts were made to grow buffer layer by chemical vapor deposition first, then a thick GaN layer by HVPE. The next step is to do the experiment and analyze with various instruments. Scanning Electron Microscope and atomic force microscopy Atomic Force Microscpoic are used to observe the surface morphology. X-ray Diffracion and transmission electron microscopy are used to know the lattice structure, and to understand the interface between the substrate and the GaN film crystal structure and epitaxial relationship. Finally, Photoluminescence spectroscopy is used to measure its optical properties and compare its defects and epitaxial quality.