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CuInSe2 chalcopyrie compound was grown heteroepitaxially on (001)GaAs substrate by molecular beam epitaxy system. Single-crystalline chalcopyrite films can be obtained by the control of substrate temperature,growth rate,and film composiion. Phase identification and crystalline orientation of CuInSe2:Ge films were examined by x-ray diffractometer.Surface morphology and microstructure were observed by electron miroscopy.Chemical composition was measured by electron probe microanalyzer.Optical and electrical properties were characterized by photoluminescence measurement,photoreflectance measurement,and four-poin probe method.

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We mainly studied the morphology of GaN structures which were grown by plasma-assisted molecular beam epitaxy. The only condition we changed is Ga/N Ratio. Based on observation of reflection high energy electron diffraction (RHEED) patterns, we found all samples belong to two-dimensional (2D) growth mode. Also, based on scanning electron microscope (SEM) analysis, we found when Ga/N Ratio is 0.13 and 0.18, the surface of sample will be smoothest. Furthermore, based on the roughness result derived from atomic force microscope (AFM), we got the same result. Then we observed the surface of samples after etching, we found all samples belong to Ga-face. Also, we can detect the degree of the state of mismatch under X-ray diffraction analysis. We found when Ga/N Ratio is 0.13, we got the lowest screw dislocation density; and when Ga/N Ratio is 0.18, we got the lowest overall dislocation density. In conclusion, we are trying to find sample growing parameters which could generate both better morphology and better structure.

We grew Mg-doped of GaN on GaN template by plasma-assisted molecular beam epitaxy (PAMBE) and measured these samples by Hall measurement, I-V curve measurement, PL, Raman scattering, SEM and AFM. The results of Hall measurement of these samples showed that the conducting type is n-type. However, I-V measurement showed these samples to have a behavior of p-n junction between Mg-doped GaN film and GaN template. For optical properties, Raman scattering spectrum did not detect a peak at 656 cm-1 which indicates Mg-N vibration; PL measurement showed the emission peak of growing samples shifted 0.03eV toward to low photon energy. The results of surface analysis showed a smooth surfaces at Ga droplet area while many pin hole was formed at ¡§dry¡¨ area. Those pin hole could be inversion domain. Futher study is going. Based on electrical, optcial, and surface analysis, the Mg-doped GaN thin film has been successful obtained by MBE. However, the hole concentration of these samples is so low that results in difficulty for Hall and Raman scatting measurement.

We invistegated the characteristic of GaN grown on LiAlO2 substrate by molecular epitaxy beam. First of all , we try to changed the growth ratio and concluded some relation between the quality of thin film. We expect to improve the quality of M-plane GaN and the size and density of c-plane GaN single-crystals by changing growth conditions. we found that when the N / Ga flow ratio decreased, that is much favor to the growth of M-plane GaN, is not favor to the growth of c-plane GaN. Further research indicates that, on entering the PA-MBE growth prior to phosphoric acid ratio of 1:50 with water to etch the surface of LAO substrate for a minute, is more suitable for M-plane GaN growth, can effectively inhibit Growth of c-plane GaN. The last series of samples, we will LAO substrate into PA-MBE system, DI water before soaking for ten minutes, we found the study can help to improve the c-plane GaN growth.

As the device size getting nanoscale, quantum dot structure had become one kind of new method of semiconductor manufacturing technology. In this thesis, two series of self-assembled InN quantum dots were grown by plasma-assisted molecular beam epitaxy (PAMBE) on GaN thin film, based on sapphire(0001) substrate. GaN thin films were characterized by the reflection high energy electron diffraction (RHEED) and scanning electron microscope (SEM). Samples with smooth epitaxial GaN thin films were obtained. Then, InN quantum dots were grown on epitaxial GaN thin film. We have prepared two series of samples. According to the results of the high resolution X-ray diffractometer (HR-XRD) and RHEED patterns, InN structure can be successfully grown on the GaN thin film surface. First series contained samples with InN layer with different thickness and changes of surface morphology were found with increase of InN layer thickness. The second series contained samples with multiple InN layers of the same thickness. Results of atomic force microscopy (AFM), RHEED patterns and SEM, show that InN quantum dots were grown as Stranski-Krastanow growth mode.

We will discuss the growth and characterization of AlxGa1-xN/GaN on sapphire substrate by plasma-assisted molecular beam epitaxy. By performing the X-ray diffraction (XRD) of our sample, we could control the fraction of Aluminum in about 0%, 16%, and 31% with varying the equivalent pressure of Aluminum. Under the investigation of field emission scanning electron microscopy (FESEM) and reflection high energy electron diffraction (RHEED) pattern, we can determinate the samples are N-polarity. The photoluminescence (PL) spectra show the bowing coefficient of AlGaN is about 1.38 eV. Furthermore, The Hall mobility could be improved from 8.2 cm2/Vs to 453 cm2/Vs or 796 cm2/Vs at room temperature or liquid nitrogen temperature respectively, after changing the structure of AlxGa1-xN, such as fraction of Aluminum, the thickness of i-AlxGa1-xN and n-AlxGa1-xN, and cap layer.

This dissertation contains two parts which is included the Gallium antimony (GaSb) thin film and quantum dots grown by ALE-MBE process. The ALE-MBE technology was used to get better film quality and to control exactly the thickness of epitaxial layers for quantum dots growth. For the larger lattice mismatch, it will be carefully controlled the substrate temperature and V/III flux ratio based on the growth mechanism to obtain the high quality of GaSb films. After fully understanding the GaSb films growth, the characteristics of GaSb quantum dots such as the density and size could be controlled. The XRD, Raman and Photo-reflectance measurements were used for obtaining the optimum growth conditions of Gasb films shown at temperature; 500~520¢Jand the V/III flux ratio about 2.5~3. The formation of three dimensional GaSb islands on GaAs substrate is expected at the deposition of a critical number of GaSb monolayer, About 3.1 monolayer grown is the optimum growth condition, and samples were characterized by atomic force microscopy (AFM). In order to control the dots size, sharp and dots density, the growth mechanism were discussed by analyzing different growth parameters included the growth temperature, thickness of monolayer, growth interruption time (GRI), and capped layer in detail.

We discuss the PL spectra of the InN band gap. The InN thin film epitaxy grows on both Si (111) and sapphire (0001) by the PA-MBE (molecular beam epi). We change different grown conditions to improve the sample quality. In experiment part, the first step is to make sure the sample is really InN, using X-ray diffraction. And then we compare the quality of all sample, by the FWHM of X-ray diffraction rocking curve and the SEM pictures.