GaN heteroepitaxy by remote plasma MOCVD : Real time monitoring by laser reflectance interferometry

Abstract
Epitaxial growth of GaN is carried out by r.f. remote plasma metalorganic chemical vapor deposition (RP-MOCVD) using trimethylgallium and N₂-H₂ plasmas as precursor of gallium and nitrogen, respectively. The RP-MOCVD leads to different growth kinetics and surface morphology depending on trimethylgallium and hydrogen fluxes. In situ laser reflectance interferometry (LRI) is used to monitor in real time the growth rate, the thickness, the surface roughness, rms, and the optical absorption of the GaN growing epilayers and their dependence on growth parameters. In particular, a strong degradation of surface morphology and GaN faceting is observed when growth is carried out under nitrogen- and hydrogen-rich conditions. Moreover, depending on the growth rate, the transition from a layer-by-layer (2D) growth to an islands (3D) growth can be discriminated by LRI. Reflectivity data are corroborated by AFM measurements.