Zinc oxide (ZnO) has gained many interests in the research of wide band-gap semiconductor materials nowadays. ZnO has attracted much attention because of its high excition bound energy (60meV), and it¡¦s promising to gain application in the field of optoelectronic such as ultraviolet light emitting devices (UV-LED) and laser diode (LD) etc. This study aims to investigate the growth condition of ZnO and to control the growth direction. ZnO was grown on LiAlO2 (LAO) (100) substrates by chemical vapor deposition (CVD) with zinc source Zn(C5H7O2)2. The different reacting temperature from 500¢J to 650¢J and the flow rate of oxygen were studied. In the result of scanning electron microscope (SEM), the surface morphology of ZnO showed two different structures, hexagonal structure and non-hexagonal film structure. And the side view of hexagonal structure showed double layers. The key factor for the transformation of double layers from film to column structure is the equilibrium of growth temperature and substrate stress. The crystals structures and epitaxial relationship were studied by X-ray Diffraction Pattern (XRD), Electron Backscattering Diffraction (EBSD). There are two kinds of ZnO epitaxial growth on LiAlO2 (100) substrate, one is c-plane of ZnO(0001)// LiAlO2 (100) and another one is m-plane of ZnO(10 0)// LiAlO2 (100), the latter one has a smaller lattice mismatch. The results of the strong UV and green emission peaking were shown in photoluminescence (PL) spectrum. Under the control of substrate temperature, c-plane polarized ZnO films were grown at 500 ¢J, and m-plane nonpolar ZnO films were grown at 650¢J. Rectangular structure could be formed between 550¢J and 650¢J. With the increase of substrate temperature, the size of rectangular became larger. At last, uniformed film would be formed at 650¢J. In addition to benefit the formation of m-plane structure, high temperature helps the sideward growth to form uniform film. In the experiment of oxygen flow, we found that c-plane hexagonal structure appeared on the m-plane film while the oxygen flow lowered to 50 sccm. And there were large numbers of oxygen vacancies measured by PL. The oxygen flow of 100 sccm is more suitable to obtain higher quality m-plane film than 400 and 50 sccm. At last, the growth time experiments were done under the growth temperament of 600¢J.Island structures of c-plane and m-plane ZnO combined with the growth time increased, and the island become larger. The XRD measurement showed that crystallinity of ZnO become better with the growth time increased.

Nonpolar free-standing GaN wafer were fabricated by using the hydride vapor phaseepitaxy(HVPE) technique on £^-LiAlO2 and (010) LiGaO2 substrates. Metallic gallium, NH3 and ultra-purity nitrogen were used as Ga and N sources. Nitrogen and hydrogen was used as the carrier gases. HCl diluted by nitrogen was designed to pass through near surface of liquid Ga to form GaCl fully. Efficaciously GaN deposition was realized by conducted steady NH3 and GaCl flows to the substrate suface, accommodated by additional hydrogen and nitrogen atmosphere flows. The influence of substrate temperature¡Bpressure¡Btime¡Band ratio of NH3/HCl (¢½/¢») on film growth was investigated. Because of the of the lattice-matched theory, Nonpolar m-plane GaN [10-10] growth on the closely lattice-matched (100) £^-LiAlO2 substrat and a-plane GaN [11-20] will growth on the [010] LiGaO2 substrate. In addition, the surface morphologies were characterized by scanning electron microscopy¡BOptical Microscope and Atomic force microscopy. Structural properties of the GaN epilayers are investigated by X-ray diffraction and transmission electron microscopy. High resolution transmission electron microscopy shows the in-plane structure. Photoluminescence (PL) spectroscopy was used to study the optical properties.

In this study, epitaxial ZnO films were grown by chemical vapor deposition (CVD) on LSAT(100) substrate. A high-quality [100] (La0.3,Sr0.7)(Al0.65,Ta0.35)O3 (LSAT) single crystal with the diameter of 60mm was grown by Czochralski pulling technique in our lab. Epi-ready LSAT substrates with rms roughness of 0.30nm ~ 0.35nm were used for all of the experiments. Nonpolar ZnO with [11-20] orientation (a-plane) was directly grown on a (100) LSAT substrate without any buffer layer by chemical vapor deposition (CVD) method. (100) LSAT single crystal substrate is loaded in a 2¡¨ quartz tube inserted to a two-temperature zone furnace. Zinc acetylacetonate hydrate (Zn(C5H7O2)2¡DxH2O, Lancaster) source was vaporized at the lower temperature of 130~140oC. The vapor was carried by a mixture of N2/O2 gas flow into the high temperature zone where the (100) LSAT substrate was located. At first, the pressure of the quartz chamber was pumped to 8¡Ñ10-3 Torr, and then kept at 150 ~ 250 Torr. The flows rates of both O2 and N2 are 500sccm. During the growth, the temperature was varied from 700 to 780oC. The growth conditions were controlled by adjusting the growth temperatures and chamber¡¦s pressures. The overall reaction was: Zn(C5H7O2)2 +12O2¡÷ZnO+ 10CO2 +7H2O Scanning electron microscope [(SEM), JEOL JSM-6330TF)] is used to examine the different surface morphologies of ZnO epitaxial film. The orientation and structure were investigated by X-ray diffraction pattern (XRD) using a Siemens D5000 X-ray diffractometer with a Cu anode at 40 kV and 30 mA. The wavelength of X-ray radiated from the Cu K£\1 is 0.1540 nm. The X-ray scan step is 0.01¢X. A JEOL 3010 scanning transmission electron microscope (STEM) operated at 200kV was employed to characterize the microstructures and orientation of the nonpolar ZnO film. Cross-sectioned TEM samples were prepared using the focus ion beam lift-out method. A Pt layer of about 8nm in thickness was pre-deposited on the sample to prevent charging. Room temperature photoluminescence (RT-PL) measurements were performed using a 325nm He-Cd laser. The emitted light was detected by a Jobin-Yvon TRIAX 550 monochromator with 0.025nm resolution.

In this study, epitaxial ZnO films were grown by chemical vapor deposition (CVD) on LAO(200) substrate. This dissertation is divided into two parts. In the first parts, the growth of ZnO films on various time was investigated. In the second part, the growth of ZnO films on various pressure was investigated. In the first parts of the dissertation, high <10-10> orientation ZnO films were grown. For a long time growth, the grown ZnO films on LiAlO2 substrate have good crystallinity, as revealed by XRD In the second parts, we discuss the difference of ZnO films by varying the growth pressure. It was found that both stripe-like ZnO(10-10) films and hexagonal ZnO(0002) grain existed at lower pressure(50~75 torr), as reveal by XRD and SEM. High <10-10> orientation ZnO films were grown at higher pressure. From cross-section TEM result, we did not find considerable dislocations in the ZnO films, and the ZnO/LiAlO2 interface is shown to be smooth and with the formation of the interlayers, which represents that ZnO and LiAlO2 have some reactions below the temperature of 650 ¢J. From the selected area diffraction (SAD) patterns, the orientation relationship between ZnO and LiAlO2 was determined as [11-20]ZnO//[001]LiAlO2¡B[0001]ZnO//[010]LiAlO2.

A hydride vapor phase epitaxy, (HVPE) was designed to grow nonpolar GaN. LiAlO2 single crystal grown by Czochralski (Cz) method in our lab was used as the substrate. The X-ray diffraction and scanning electron microscopy were used to study the GaN epilayer¡¦s orientation and surface morphology. At the first part, we used the c-plane sapphire as substrate and make sure that our HVPE reactive system is working. And the second part, we used LiAlO2 substrate to grow non-polar GaN substrate. After the growth, GaN was separated from LiAlO2 substrate and become free-standing. We found that as-grown GaN has both c-plane (0001) and m-plane (10-10) orientations. After some improvements, we got a nonpolar GaN substrate. But the m-plane (10-10) GaN grains are random. The photo-luminescence¡]PL¡^showed that the light emissive quality of these two GaN thick film are well. We will keep improving the design of our HVPE.

Nonpolar m-plane ZnO epitaxial film with [10-10] orientation and a-plane ZnO epitaxial film with [11-20]was successfully grown on a large-size [100] and [010] LiGaO2 (LGO) single crystal substrate by chemical vapor deposition (CVD) method. The dependence of growth characteristics on the different growth conditions was investigated. Following the CVD growth, the surface morphologies and epi-film crystallinity were studied by a scanning electron microscopy and X-ray diffraction. Room temperature photoluminescence spectra exhibit a strong near-band-edge emission peak at 377 nm with a negligible green band. Further structural characterizations and defect analysis of nonpolar ZnO material were performed using transmission electron microscope (TEM). This thesis included two different orientations ZnO film. First was ZnO[10-10], which can get good epi-film crystallinity and flat surface morphologies under 750¢J. And we tried to grow under different pressure, the data shown that higher pressure(more than 150 torr) tended to grow ZnO[10-10] orientation on LGO[100] substrate. The other one was ZnO[11-20]. We can get flat and continuous ZnO[11-20] film under 680¢J.

In this work, Nitridated b-LiGaO2 substrates have been used to grow nonpolar a-plane ZnO epitaxial films by a homemade thermal chemical vapor deposition. We control the quality of the films by adjusting the deposition position, growth temperature and oxygen partial pressure. The properties of the ZnO films was investigated by x-ray diffraction(XRD), scanning electron microscopy(SEM), atomic force microscopy(AFM), photoluminescence spectra(PL), Raman spectra(Raman) and transmission electron microscopy(TEM). The results show that the crystal quality, surface morphology and optical properties of a-plane ZnO films are strongly related to the deposition position and growth temperature. It is also found that the surface roughness of the ZnO films gets more smoothly with increasing the oxygen partial pressure. Up to now, ZnO films grown at 700¢J diplay the best crystal quality, the full width at half maximum values of (11-20)ZnO omega scan rocking curve is 0.5¢X. In comparison with above growth condition, it demonstrate better optical properties by shortening deposition position and increasing growth temperature to 750¢J. Room temperature PL spectra exhibit a strong near band edge emission and a negligible green band. Furthermore, low temperature PL spectra is dominated by neutral donor-bound excitons and free electron-to-bound emission. From the TEM selected area diffraction patterns and the XRD phi angle scan, the epitaxy relationship between ZnO and LGO is determined as [001]LGO//[0001]ZnO and [100]LGO//[10-10]ZnO. XRD omega-two theta scan and Raman spectra analysis are carried out to characterize the status of the strain in ZnO film is compressive, the reason is illustrate in detail.

Pure m-plane p-GaN/InGaN/n-GaN on the m-sapphire grown by plasma assisted molecular beam epitaxy (PAMBE) had been achieved. V/III ratio of the first layer m-plane GaN is 20 and growth temperature is 665 ¢XC. ¢½/¢» ratio and the growth temperature are the most important factors in the growth sequence. M-InGaN film with better crystal quality was grown successfully by tuning these two factors. We have obtained a narrow window for epitaxial growth of m-plane InGaN/GaN on m-sapphire at 450 ¢XC. The striated surface is along (1120) a-axis direction of m-InGaN epilayer. As the growth temperature is increased further to 550 ¢XC, there is no InGaN signal from x-ray diffraction (XRD). We study the effect of growth condition on the structural properties and morphology of these films using high-resolution x-ray diffractometer (XRD) and scanning electron microscopy (SEM)

Zinc Oxide (ZnO) has great potential for applications on ultraviolet/blue light emitting devices because of high exciton binding energy and low cost. This research use low lattice-mismatched £^-LiAlO2 (LAO) substrate to grow ZnO epitaxial films by chemical vapor deposition (CVD). The first part of the present study deals with effect of processing parameters including temperature of Zinc procuser, sample position and growth temperature on ZnO epilayer. High the precuser temperature and long distance between sample and center of CVD furnace resulted in high growth rates. When growth rate was low, (10 0) ZnO (m-ZnO) was obtained and its crystallinity and luminescence property were poor. After increasing the growth rate to a certain extent, the surface of epilayer was flat and the crystallinity was improved. A further increase of growth rate resulted in a mixture of m-ZnO and c-plane in the ZnO epilayer. Based on the first part of study, the second part was focused on examining the effect of a nanosized buffer layer on inhibiting the nucleation of c-plane ZnO. Results showed that the nucleation of c-plane ZnO was indeed inhibited at low growth temperature. Finally, the crystallinity the optical property of the epilayer were improved by introducing a thick and flat buffer layer of ~170 nm in thickness.

Ce travail concerne l'intégration, par épitaxie sous jets moléculaires (EJM), de matériaux nitrures d’éléments III (en particulier GaN) sur des substrats et couches tremplins à base d’oxyde de zinc (ZnO). L’objectif était la réalisation et l’étude d’hétérostructures nitrures de type puits quantiques (PQs) (Al,Ga)N/GaN et (In,Ga)N/GaN, en vue d’évaluer leurs potentialités pour la réalisation de diodes électroluminescentes (LEDs). En particulier, deux orientations cristallographiques ont été étudiées : le plan « polaire » (0001) (dit plan C) et le plan « non polaire » (11-20) (dit plan A). Les couches de GaN orientées suivant le plan A (11-20), « a-GaN », ont été épitaxiées sur des tremplins de (Zn, Mg)O (11-20) / saphir (10-12) réalisés par EJM. L’anisotropie de la morphologie de surface, de la microstructure cristalline, ainsi que de l'émission optique des couches de a-GaN, a été mise en évidence. Une série d'échantillons de PQs de a-(GaN/Al0.2Ga0.8N) avec des épaisseurs de puits différentes a été fabriquée, et l'absence d’effet Stark quantique confiné dans ces hétérostructures a été établie. Des procédés de croissance de GaN sur des substrats de ZnO massifs d’orientation A, « a-ZnO », et C, « c-ZnO », ont également été développés. En particulier, des couches de GaN (0001), « c-GaN », avec une polarité Ga- ou N- ont été épitaxiées sur la face O de substrats c-ZnO. Les mécanismes de détermination de la polarité ont été analysés. Des LEDs bleues contenant une zone active constituée de PQs (In, Ga)N / GaN ont été réalisées sur des substrats c-ZnO. Des puissances de sortie atteignant 40 µW à 20 mA et 0,1 mW à 60 mA ont été mesurées. Enfin, des PQs (In, Ga)N / GaN ont été fabriqués sur substrats a-ZnO et comparés à des PQs fabriqués sur c-ZnO avec des conditions de croissance équivalentes. Les résultats indiquent une concentration en In plus importante dans le cas des PQs épitaxiés sur c-ZnO et une polarisation de l’émission de PL suivant la direction <1-100> dans le cas des PQs épitaxiés sur a-ZnO. / This work focus on the integration of III-nitride materials, by molecular beam epitaxy (MBE), on ZnO based templates and substrates. The objective is to explore the potential of (Al,Ga)N/GaN and (In,Ga)N/GaN multi-quantum wells (MQWs) grown on ZnO for the fabrication of light emitting diodes (LEDs). In particular, two crystal orientations are studied: the polar (0001) plane (c-plane) and the nonpolar (11-20) plane (a-plane). The structural and optical properties of epitaxial layers are mainly characterized by AFM, SEM, XRD, TEM and PL. A-plane (11-20) GaN layers have been grown on a-(Zn,Mg)O/r-sapphire templates by MBE. The surface morphology, the crystal microstructure, as well as the optical emission of a-GaN layers show strong anisotropic properties. A series of a-plane Al0.2Ga0.8N/GaN MQWs with different well thicknesses have been fabricated and the absence of quantum confined Stark effect in these nonopolar heterostructures has been evidenced. Processes of growing GaN on both c- and a- plane bulk ZnO substrates have been developed. In particular, GaN layers with either Ga- or N- polarities have been grown on O face ZnO, and their polarity determination mechanisms have been analyzed. (In,Ga)N/GaN MQWs based blue LEDs have been demonstrated on c- ZnO substrates. Output powers of 40 µW at 20 mA and 0.1 mW at 60 mA have been measured. Finally, a-plane (In,Ga)N/GaN MQWs are fabricated on bulk a-ZnO substrates and compared with c-plane MQWs grown under similar conditions. PL measurements indicate that a-plane MQWs exhibit a lower In incorporation efficiency and a polarized emission along <1-100> direction.