Effect of In Situ Thermal Cycle Annealing on GaN Film Properties Grown on (001) and (111) GaAs, and Sapphire Substrates |
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Authors: | Kun Wang Dimitris Pavlidis Jun Cao |
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Affiliation: | (1) Solid State Electronics Laboratory, Department of Electrical Engineering and Computer Science, The University of Michigan, 48109 Ann Arbor, MI |
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Abstract: | The effect of in-situ thermal cycle annealing (TCA) has been investigated for GaN growth on GaAs(lOO), GaAs(111) and sapphire
substrates. X-ray diffractometry (XRD) and surface morphology studies were performed for this purpose. Enhanced cubic phase
characteristics were observed by employing annealingfor GaN layers grown on (001) GaAs. The thickness of the layer subject
to annealing is critical in determining the phase of the subsequently grown layer. Thin initial layers appear to permit maintenance
of the cubic phase characteristics shown by the substrate, while hexagonal phase characteristics are manifested for thick
initial layers. Higher temperature of annealing of thick pre-annealed layers results in changes from mixed cubic/hexagonal
phase to pure hexagonal phase. Growth on GaAs(111) substrates showed single cubic phase characteristics and similar enhancement
of crystal quality by using TCA as for layers on GaAs(OOl). Micro-cracks were found to be present after TCA on GaAs(lll) substrates.
Thermal cycling also appears to be beneficial for layers grown on sapphire substrates. |
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Keywords: | GaN lattice mismatch metalorganic chemical vapor deposition (MOCVD) thermal cycle annealing |
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