Monitoring the formation of GaN nanowires in molecular beam epitaxy by polarization-resolved optical reflectometry

We analyze the temporal variation of the substrate optical reflectance during the formation of GaN nanowires in molecular beam epitaxy using transverse electric and transverse magnetic polarized light. The time dependence of the reflectance signal is simulated using an effective medium approach that takes into account the spatial fluctuations in the length and density of the nanowire ensemble within the area probed by the laser beam. Our study demonstrates that optical reflectometry is a powerful technique to detect the onset of nanowire nucleation, assess the deposition rate, and estimate the fluctuations in the nanowire length and covered area fraction at the μm scale.