Studies of InAs and GaAs layers prepared by molecular beam epitaxy
This thesis describes a study of the growth and doping of single crystal thin films of GaAs and InAs by the technique of molecular beam epitaxy (MBE). One micron thick unintentionally doped films of InAs were deposited onto GaAs substrates at the relatively low growth temperature of 370°C and GaAs films were grown over the range 400 - 650°C. A detailed study of the doping properties of silicon in GaAs films was also made. The epilayers were characterized using the van der Pauw technique and Hall measurements, Schottky barrier C-V profiling, photoluminescence analysis, X-ray diffraction, scanning electron microscopy, Rutherford backscattering and in-situ reflection medium energy electron diffraction. The GaAs:Si material was further characterized by the assessment of Mott barrier diodes fabricated from n/n+ structures. The study has been primarily concerned with investigating the relationships between the MBE growth parameters (e.g. growth rate, growth temperature, group III - group V flux ratio, role of the buffer layer) and the properties of the epilayers. The experimental parameters were found to significantly influence the electrical and optical properties of the layers. An analysis of these effects is presented which shows that the growth parameters determine the extent and nature by which dopant and system derived impurity species as well as defects are incorporated into the layers. The origin and type of some impurities associated with the construction of the MBE system were identified.
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