| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS+EM+TF-ThA |
| Session: | Atomic Layer Processing: Integration of ALD and ALE |
| Presenter: | Samantha G. Rosenberg, U.S. Naval Research Laboratory |
| Authors: | S.G. Rosenberg, U.S. Naval Research Laboratory D.J. Pennachio, University of California, Santa Barbara M. Munger, SUNY Brockport C. Wagenbach, Boston University V.R. Anderson, U.S. Naval Research Laboratory S.D. Johnson, U. S. Naval Research Laboratory N. Nepal, U.S. Naval Research Laboratory A.C. Kozen, U.S. Naval Research Laboratory J.M. Woodward, U.S. Naval Research Laboratory Z.R. Robinson, SUNY Brockport K.F. Ludwig, Boston University C.J. Palmstrøm, University of California, Santa Barbara C.R. Eddy, Jr., U. S. Naval Research Laboratory |
| Correspondent: | Click to Email |
We have previously shown that using our low temperature plasma-assisted atomic layer epitaxy (ALEp) method we can grow AlN and InN for various applications.1-3 The materials we have grown using our ALEp method have shown good crystalline quality, but suffer from an incorporation of carbon. Theory has led us to believe that the substrate preparation plays a significant role in the remediation of carbon, as that surface becomes the interface for the growth of the III-N film. Therefore, using surface science techniques, we strive to develop not only a fundamental understanding of the ALEp growth process but also atomic layer processes that will result in the best preparation method for a pristine GaN starting surface for ALEp.
In-situ surface studies of in-situ and ex-situ GaN substrate preparation and InN ALEp growth were conducted to advance fundamental understanding of the ALEp process. We conduct in-situ grazing incidence small angle x-ray scattering (GISAXS) experiments at the Cornell High Energy Synchrotron Source to investigate growth surface morphological evolution during sample preparation including a gallium-flash-off atomic layer process (ALP) at varying temperatures and number of cycles. GISAXS information is complemented with in-vacuo x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and ex-situ atomic force microscopy studies conducted at the Palmstrøm Lab at UCSB, where we consider different ex-situ sample preparation methods to produce the most suitable GaN surface for our ALP/ALEp-based approach. We have determined that a combination of UV/ozone exposure followed by an HF dip produces the cleanest and smoothest GaN surface. We have further determined with GISAXS that ALP-based gallium-flash-off experiments performed at higher temperatures (500°C) produce a smoother starting surface than lower temperatures. Additionally we have determined that we should only perform ~10 cycles of ALP gallium-flash-off instead of 30 as was empirically chosen previously. Due to the sensitivity of the GISAXS experiment, we are able to observe the effect of individual components of the ALP process cycle (pulse vs purge), leading us to insights on the underlying chemical process of the gallium-flash-off ALP. Combining these two results, ex-situ and in-situ cleaning preparation, should lead us to the best GaN starting surface to grow high quality crystalline InN films.
[1] N. Nepal, et al., Appl. Phys. Lett. 103, 082110 (2013)
[2] C. R. Eddy, Jr, et al., J. Vac. Sci. Technol. A 31(5), 058501 (2013)
[3] R. S. Pengelly, et al., IEEE Trans. Microwave Theory Tech. 60, 1764 (2012)