| AVS 65th International Symposium & Exhibition | |
| Thin Films Division | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Film Poster Session |
| Presenter: | Jeffrey Woodward, American Society for Engineering Education (residing at U.S. Naval Research Laboratory) |
| Authors: | J.M. Woodward, American Society for Engineering Education (residing at U.S. Naval Research Laboratory) S.G. Rosenberg, American Society for Engineering Education (residing at U.S. Naval Research Laboratory) N. Nepal, U.S. Naval Research Laboratory S.D. Johnson, U.S. Naval Research Laboratory C. Wagenbach, Boston University A.C. Kozen, American Society for Engineering Education (residing at U.S. Naval Research Laboratory) Z.R. Robinson, The College at Brockport - SUNY D.R. Boris, U.S. Naval Research Laboratory S.G. Walton, U.S. Naval Research Laboratory K.F. Ludwig, Boston University C.R. Eddy, Jr., U. S. Naval Research Laboratory |
| Correspondent: | Click to Email |
Plasma-assisted atomic layer epitaxy (ALEp), a variant of atomic layer deposition in which relatively higher temperatures are utilized to promote surface diffusion for epitaxial growth, offers several potential advantages over conventional growth methods such as metalorganic chemical vapor deposition and molecular beam epitaxy for the epitaxy of III-N materials and device structures. These advantages include significantly lower growth temperatures and highly controlled layer thicknesses, the latter of which is the result of the sequential pairs of self-terminating and self-limiting reactions that constitute the growth process. However, ALEp is a relatively new method for III-N growth, and significant efforts will be required to better understand the nucleation and growth kinetics. To this end, grazing incidence small-angle X-ray scattering (GISAXS) has been previously utilized for the study of surface morphology during the ALEp growth of InN1 and AlN2 on a-plane Al2O3 substrates. GISAXS is a non-destructive technique that can probe electron density fluctuations on length scales ranging from approximately 1 nm to 250 nm in an integral manner3, making it well-suited to the study of epitaxial growth. The resulting intensity distribution from a set of scattering objects is related to the form factor and structure factor, which are the Fourier transforms of functions describing the object shape and spatial arrangement, respectively.
In this work, we present data from in situ GISAXS studies performed at the Cornell High Energy Synchrotron Source during the ALEp growth of InN on bulk GaN substrates. Two growth parameters were investigated independently: temperature (180 °C, 250 °C, and 320 °C) and the ratio of N2 to Ar gas flows into the plasma source (75/200, 31/244, and 15/260). The GISAXS patterns were analyzed in order to extract information about the evolving morphologies. The data indicate that InN islands nucleated with greater density at 180 °C than at 250 °C and 320 °C, and that the island density decreased as the growth progressed for all temperatures. While the initial areal densities and island diameters at 250 °C and 320 °C were approximately identical, the density and diameter of the latter exhibited more significant decrease and increase, respectively, with time, which may indicate a temperature-dependent coarsening due to island coalescence or Ostwald ripening. The gas flow ratio had minimal effect on diameter and density, but influenced the island shape.
[1] N. Nepal et al., J. Vac. Sci. Technol. A 35,031504 (2017)
[2] V. R. Anderson et al., J. Vac. Sci. Technol. A 35, 031508 (2017)
[3] G. Renaud et al., Surf. Sci. Rep 64 (2009) 255-380