inasgasb超晶格界面微观结构研究-study on microstructure of inas gasb superlattice interface.docx

AbstractAs a promising photoelectric materials, GaSb-based materials such as GaSb/GaAs and InAs/GaSb superlattices have made great progress in the fields of infrared detector in recent years. In this dissertation, growth method, dislocation distribution, structure and electrical properties of GaSb epilayer and InAs/GaSb superlattices grown on GaAs substrates by Molecular Beam Epitaxy (MBE) were investigated systematically.The growth of highly mismatched GaSb epilayer on GaAs (001) substrates was studied both experimentally and theoretically. The two-step growth method was used and low-temperature buffer layer was introduced in order to improve the quality of the GaSb epilayer. The growth parameters of low temperature (LT) GaSb buffer layer (including growth rate, thickness, and V/III beam equivalent pressure ratio ) were studied and it was found that the optimum growth rate, thickness, and V/III beam equivalent pressure ratio of the LT GaSb buffer were 1.43μm/h, 20nm and 3.0 respectively. The LT buffer restricted the formation of the 60° misfit dislocations(MDs) during the initial GaSb epilayer growth process and then reduced the density of the threading dislocations(TD) in the epilayer.The observation of TEM shows high density dislocations in the GaSb epilayer on GaAs substrates, including the TD in the {111} glide plane and the 90°MDs at the interface of the GaSb/GaAs. GaSb epilayers grown on GaAs (001) vicinal substrate 4° misoriented towards [110] direction were studied using high resolution X-ray diffraction (HRXRD). We found that the densities of TDs in(111) plane were higher than in (1 11) plane and the TDs have a bigger spacingin the [110] direction than in [1 10] direction. This is a consequence of the unequal distribution of stress due to the miscut substrate and associated with the shape of GaSb island. The investigation of the tilt in the GaSb epilayer shows that the formation of 60° MDs is later than 90° MDs.The electrical properties of undoped GaSb