The mechanism for growth of single-crystal GaN on oxidized AlAs (AlOx)
formed on a Si(111) substrate by metalorganic chemical vapor deposition has been studied. Cross-sectional transmission electron microscopy (XTEM) indicates that the grown GaN is single-crystal α-GaN in spite of the fact that the AlOx
on which the GaN is grown is found to contain predominantly polycrystal γ-Al2O3.
Reflection high-energy electron diffraction (RHEED) shows that oriented crystallized α-Ga2O3
is formed between AlOx
and the GaAs cap layer during the oxidation process. The α-Ga2O3
acts as a growth template and results in the crystalline orientation of α-GaN on polycrystal γ-Al2O3.
Further support for this template is derived from energy dispersive x-ray spectroscopy that shows the existence of Ga atoms on AlOx.
Combined XTEM/RHEED analysis suggests that α-GaN is oriented in the growth direction as α-GaN∥α-Ga2O3∥Si
and the in-plane direction as α-GaN∥α-Ga2O3∥Si,
which can be understood by considering the misfit in the in-plane atomic separation at each interface. © 1998 American Institute of Physics.