Structural property analysis of GaN grown on GaAs by movpe using transmission electron microscopy

Abstract

Transmission electron microscopy (TEM) observation has been performed on the micro-(nano-) structure of GaN films grown on GaAs (001) substrates by metalorganic vapor phase epitaxy (MOVPE). Based on our results of x-ray diffraction (XRD) and electron diffraction (ED), the GaN grown films have a zincblende structure, i.e., a cubic structure or c-GaN. For lower growth temperatures (900-920 degrees Selsius), cross-sectional TEM micrographs and ED patterns demonstrate that the GaN grown films contain bands of stacking faults (SFs) and twins parallel to (111) planes. Besides, the density of SF and twin defects decreases with the distance from the interface of c-GaN/GaAs. No different type of single diffraction spots on the ED pattern was observed. On the other hand, the GaN films exhibited a transition from cubic to mixed cubic/hexagonal phase under conditions of increasing growth temperature (T[ subscript g] 960 degrees Selsius) as determined by using TEM-selected area diffraction (SAD) technique with complementary XRD and PL observations. In addition, the luminescence characteristics of c-GaN films are shown to be very sensitive to the presence of the single-crystal hexagonal GaN (h-GaN). T [ subscript g] and the formation of (111) facets on the top surface of c-GaN and on the interface of C-GaN/GaAs play an important role in growing high cubic-phase purity c-GaN films with low density of planar defects (SFs and twins) and without incorporation of single-crystal h-GaN.