Surface termination during GaN growth by metalorganic vapor phase epitaxy determined by ellipsometry

Spectroscopic ellipsometry is used to study GaN films during growth by metalorganic vapor phase epitaxy (MOVPE) in correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). Results for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions, which are attributed to the presence of a Ga bilayer on the surface (also seen with low energy electron diffraction) in the Ga-rich case. Results for MOVPE surfaces during growth or for surfaces which are stabilized under NH3 are very similar to the N-rich PAMBE result. It is concluded that under normal growth conditions in MOVPE in contrast to PAMBE the surface is not terminated by a Ga bilayer. © 2003 American Institute of Physics.</em