Understanding the effect of nitrogen plasma exposure on plasma assisted atomic layer epitaxy of InN monitored by real time grazing incidence small angle x-ray scattering

The authors present an in situ study of the effect of nitrogen plasma pulse time on the temporal evolution of the surface morphology of InN growth on a-plane sapphire at 250 °C by plasma assisted atomic layer epitaxy (ALEp). The growth surface evolution was monitored in real-time using grazing incidence small angle x-ray scattering (GISAXS) measurements at an x-ray incidence angle of 0.8°. Nitrogen plasma pulse time (tp) was varied between 15 and 30 s in 5-s steps, and for all tp, the near specular scattering broadens and correlated peaks develop and evolve along the Yoneda Wing (YW). For tp ≥ 20 s, a YW with one correlated length scale evolves. At the end of the growth, the longest correlated length scale is 16.54 nm for tp = 25 s. Porod analysis of GISAXS intensity at high qy for tp = 25 s shows the formation of mounded shapes at the early stage of nucleation that transitioned to cylinders after about 3 unit cells of InN growth. Additionally, at tp = 25 s, the growth rate is highest with root mean squar...