AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThM

Paper EM-ThM11
Optimization of the Nitridation of Sapphire Substrates Using a Fractional Factorial Designed Experiment

Thursday, November 5, 1998, 11:40 am, Room 316

Session: Compound Semiconductor Surface Chemistry
Presenter: T.J. Kropewnicki, Georgia Institute of Technology
Authors: T.J. Kropewnicki, Georgia Institute of Technology
P.A. Kohl, Georgia Institute of Technology
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Future advances in the performance of wide bandgap microelectronic devices depend on further improvements in the quality of the materials from which these devices are fabricated. Nitridation of the substrate is an important step that promotes the growth of high quality Group III nitride semiconductors; however, very few systematic studies of the nitridation process have been done. Herein, we report on a fractional factorial designed experiment to optimize the nitridation of sapphire substrates for the subsequent growth of GaN by plasma assisted molecular beam epitaxy (MBE). The sapphire substrates were nitridated with hydrazine using a process described elsewhere.@footnote 1,2@ Single replicates of a 2@super4-1@ fractional factorial design were performed. The investigated factors were the pretreatment of the sapphire substrate with a 3H@sub 2@SO@sub 4@ : H@sub 3@PO@sub 4@ etch prior to introduction into the reactor, an in situ H@sub 2@ cleaning step prior to nitridation, the substrate temperature, and the nitridation time. Four center points were included in the design to test for nonlinearity and to yield an estimate of the experimental error. The material properties used to assess the quality of the nitridated surfaces were the nitrogen content of the surface (as measured by x-ray photoelectron spectroscopy) and the surface roughness (as measured by atomic force microscopy). Bulk GaN films were then grown on each of the nitridated sapphire substrates by r.f. plasma assisted MBE. The bulk growth conditions were determined with a separate designed experiment,@footnote 3@ and these conditions were held constant for each of the growths. The influence of the nitridated surfaces on the quality of the bulk GaN films was studied by photoluminescence and x-ray diffraction. The results of this fractional factorial designed experiment as well as their impact on the growth of GaN on sapphire substrates will be discussed. @FootnoteText@ @footnote 1@T. Kropewnicki and P. Kohl, "Hydrazine Cyanurate as a Nitrogen Source for Thin Nitride Film Growth," Journal of Vacuum Science and Technology A, 16 (1), 139 (1998). @footnote 2@T. Kropewnicki and P. Kohl, "Nitridation of Substrates with Hydrazine Cyanurate for the Growth of GaN," Proceedings of the 1998 Spring MRS Meeting, San Francisco, CA, April 1998. @footnote 3@K. Lee and G. May, unpublished.