Growth Of High Quality Silicon Germanium With Nano-templates

Because of its unique physical and chemical properties, germanium shows great potential for device applications in microelectronics and optoelectronics. Moreover the compatibility with conventional silicon-based CMOS processes makes Ge more attractive than other semiconductor materials. Ordered Ge quantum dots (QDs) with high density and uniform size can be used to fabricating IR photodetectors, single electron devices, Si-based light emitters and maybe quantum computers. Ge films with low dislocation density have great application potential for IR photodetectors and multi-junction solar cells.In this dissertation, molecule beam epitaxy (MBE) method was exploited to fabricate Ge QDs and films. The density, size, shape and site of Ge QDs and dislocation density of Ge films under different conditions were investigated. Several characterization methods, such as Scanning Electron Microscope, Atomic Force Microscopy Raman Spectrometer, Etch Pit Density and Reflected High Energy Electron Diffraction (RHEED) were used to characterize samples.The main part and the innovation point of this dissertation is growth of high quality Ge QDs using porous alumina membranes (PAMs) direct as templates. We had a systemic and detailed discussion and reasonable analysis on the morphology and structural characteristics of Ge QD arrays, which were attributed to introduction of PAMs, substrates temperature, deposition amount of Ge and aspect ratio of PAM pores. The long-range well-ordered Ge QD arrays formed a duplication of PAM at500℃, while the hexagonal packed Ge QD arrays were complementary with PAM at400℃. Caused by the coeffect of substrate temperature and PAM, an obviously increasing trend of size was found as the substrate temperature decreased from600℃to400℃. Different shapes of Ge QDs with different aspect ratios of PAMs were discovered. Utilizing a geometrical optic method and kinetics, the mechanism of Ge QDs with such shapes was well discussed. Additionally, distinct tensile strain was found in Ge QDs which was beneficial for potential fabrication of light emitters. In this dissertation, selective growth of Ge films was also studied. We grew Ge films selectively on the substrates covered by a layer of silica nanospheres using spin coating self-assembly method and electrostatic self-assembly method, and finally obtained high quality Ge films with low dislocation density. We studied different growth stages by RHEED, and explained the forming mechanism of the terrace structures found after growth. By comparing with the comparison, the quality of Ge film by selectively growing was evaluated.The study of growth of high quality SiGe materials with nanotemplates builds the foundation for the development of growth of high quality SiGe materials and the study of SiGe-based devices.