| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF+AS+NS+SA-ThM |
| Session: | Thin Film: Growth and Characterization, Optical and Synchrotron Characterization I |
| Presenter: | Virginia Anderson, US Naval Research Laboratory |
| Authors: | V. Anderson, US Naval Research Laboratory N. Nepal, US Naval Research Laboratory S.D. Johnson, US Naval Research Laboratory A. DeMasi, Boston University J.K. Hite, US Naval Research Laboratory K.F. Ludwig, Boston University C.R. Eddy, Jr, US Naval Research Laboratory |
| Correspondent: | Click to Email |
Aluminum nitride, gallium nitride, and indium nitride have desirable qualities for many semiconductor applications, and have recently been studied intensely.1 Because of their direct, tunable band gaps and capacity for high current density they are attractive for photovoltaics and high power transistors. The current methods of depositing high-quality III-nitride films, are metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). The temperatures for the depositions make ternaries challenging. Indium nitride, for example, is difficult to mix with aluminum nitride, as typical MOCVD temperatures for AlN and for InN are 1000°C and 450°C respectively. Aluminum nitride deposition with atomic layer epitaxy (ALE) is currently being explored by some groups as a fabrication friendly technique for thin films at lower temperatures.2
Crystalline AlN deposited with plasma assisted ALE (PA-ALE) in a Fiji reactor from Ultratech/Cambridge Nanotech at 500°C currently has lower material purity than the AlN deposited by MBE and MOCVD, and understanding the film deposition mechanism in order to improve quality is the subject of ongoing research.3 There is a need for a better understanding about the film evolution during nucleation. Grazing incidence small angle x-ray scattering (GISAXS) is sensitive to changing surface features and can be conducted at a wide range of pressures, making it useful for real time monitoring of deposition.4
AlN deposited by PA-ALE was grown using trimethylaluminum and hydrogen/nitrogen plasma pulses in a custom reactor at the Brookhaven National Synchrotron Light Source and the Cornell High Energy Synchrotron Source. In both instances, GISAXS was used to examine surface changes during the deposition.
GISAXS information collected during AlN growth at nominally 400°C, 450°C, and 500°C suggested that temperature influenced nucleation, with changes in roughening behavior observed. Post-growth examination of the AlN films with x-ray photoelectron spectroscopy and atomic force microscopy gave important information on the final film elemental composition and morphology. The GISAXS data also show that the surface continued to evolve during the cooling after growth completion while still in the reactor. This information only adds to the necessity of in situ growth monitoring to fully understand the mechanisms involved in the ALE growth process.
References:
1 M. Mori et al., Appl. Phys. Express 5 082301 (2012)
2 M. Bosund et al., Appl. Surf. Sci. 17 7827 (2011)
3 N. Nepal et al., Appl. Phys. Lett. 103 0 82110 (2013)
4 K. Devloo-Casier et al., Appl Phys. Lett. 98 231905 (2011)