Microstructural assessment of cubic InN film grown by molecular beam epitaxy

Abstract

In the thesis, structural modification and crystal quality of cubic InN (c-InN) films grown on GaAs (001) substrates by molecular beam epitaxy have been systematically investigated and analyzed. The effects of growth conditions, namely In- and N-rich conditions, are established. Based on high-resolution X-ray diffraction, the result demonstrates that all the InN grown films have a cubic structure. On the other hand, electron diffraction (ED) pattern and cross-sectional transmission electron microscopy (TEM) micrographs demonstrate that the InN grown films contain a high density of stacking faults (SFs) parallel to (111) planes. Besides, the density of SF and twin defects decreases with the distance from the interface of c-InN/GaAs. No different type of single diffraction spots on the ED pattern was observed. On the other hand, TEM micrographs the ED patterns demonstrate that the c-InN films exhibited a transition from cubic to mixed cubic/hexagonal phase under N-rich growth conditions. In addition, µ-Raman scattering spectra obtained from these InN layers confirmed the existence of a structural modification from cubic to mixed cubic/hexagonal phase in microstructure of the N-rich layers, which exhibit higher hexagonal-phase incorporation than that of the In-rich layers. Our results suggest that the growth condition is a key parameter in the growth of high cubic phase purity c-InN films with lower incorporation of single-crystal h-InN.