High Resolution X-ray Diffraction Characterization of III-Nitride Semiconductors: Bulk Crystals and Thin Films.

摘要

As III-nitrides continue to evolve into a homoepitaxial growth scenario, the development of non-traditional metrologies for the proper study of III-nitride single crystals and homoepitaxial thin films becomes critical. To this purpose, the work presented in this dissertation has focused on the development and application of suitable high resolution X-ray diffraction (HRXRD) methods, desirable for their sensitivity, accuracy and non-destructive nature. HRXRD techniques were explored and developed for the identification of polishing-induced damage in processed III-nitride single crystals, the structural analysis of non-polar AlN homoepitaxial films grown on AlN single crystals and the assessment of alloy film characteristics of AlxGa1-xN epilayers deposited on AlN substrates.;AlN and GaN substrates were treated to various degrees of mechanical polishing and chemical mechanical polishing (CMP). Gross damage created from aggressive polishing was readily quantified using X-ray rocking curve (XRC) peak broadening and diffuse scatter intensity. However, once the wafers were exposed to CMP treatment, it was found that the use of line scanning methods was unable to distinguish the effects of CMP time exposure on the crystal surface. Alternatively, the analysis of surface-related diffraction features recorded from on- and off-axis high-resolution reciprocal space maps (RSMs) allowed the classification of remnant damage in CMP-treated substrates as a function of CMP exposure time. By comparing the crystal truncation rod intensity and the pole diffuse scatter magnitude, differences at the near-surface regions of CMP-processed wafers were qualitatively and quantitatively measured. For AlN, the mapping of the (101¯3) reflection, observable under grazing incidence conditions, was introduced as an effective HRXRD method to analyze the crystal surface of AlN substrates using a laboratory source.;HRXRD methods were employed on high-quality non-polar homoepitaxial AlN films grown on m-plane AlN single crystals by metalorganic chemical vapor deposition. The films were deposited under identical growth conditions, within a temperature range between 1150&;The strain state and composition of AlxGa1-xN alloy epitaxial films deposited on (0001) AlN single crystals by MOCVD was studied using several HRXRD methods, including relative lattice parameter measurements (zone-axis techniques) and RSMs. Within the investigated compositional range, all alloy films were revealed to be pseudomorphic to the AlN substrate. However, crystallographic tilting was observed for several cases, which led to large errors in extracted biaxial stress relaxation values. To eliminate measurement error and further explore film tilting as a potential in-plane stress relaxation mechanism, alloy films were grown on 0.2&