Electrical and optical properties of indium nitride and indium-rich nitrides prepared by molecular beam epitaxy for opto-electronics applications

Great interest in III-nitride semiconductors has been driven by the significant technological importance of this material system. GaN and its alloy have been used in the fabrication of a range of electronic and photonic devices. Blue light emitting diode and laser diode with InGaN as the active layer have been commercialized for several years. Due to such technological importance, considerable research efforts have been made to understand the fundamental properties of III-N semiconductors. However, unlike the intensively studied GaN, InGaN and other nitride compounds, InN, which is also an important component of the III-N system, remains the least studied nitride material. This is mainly due to the difficulty in preparation of high-quality InN epilayers. Two of the main difficulties are the lack of suitable substrate material and the low dissociation temperature of InN. As a result, many fundamental parameters of InN were adopted from some very early reports based on polycrystalline InN films produced by RF sputtering method. Those reports are seemingly good but have never been repeated.; This thesis reports epitaxial growth of InN and In-rich nitrides by molecular beam epitaxy. The optimum growth conditions of InN were investigated, which results in the best electrical properties of InN film reported in recent years. For the first time, non-degenerate InN film was produced and the surface charge accumulation of InN films was identified. Detailed and original structural characterizations were carried out. By collaborating with outside labs, many fundamentals properties of InN were measured or rediscovered. One of the main accomplishments in the study is the discovery of the narrow fundamental bandgap of InN, which is around 0.7 eV instead of the widely accepted 1.9 eV. This significant result provides new research guidance for the scientific community. By further preparing In-rich nitrides, the bowing parameters of InGaN and InAIN were first accurately measured. For the first time, the “III-N triangle” was fully established.