Characterization of chrystallographic properties and defects via X-ray microdiffraction in GaN(0001) layers

Rozaliya I. Barabash G E. Ice 3C Roder S. Figge Sven Einfeldt Detlef Hommel 4T. M. Kantona James S. Speck S. P. DenBaars 1R. F. Davis 2

1. University of California, Santa Barbara, CA 93106, United States
2. North Carolina State University (NCSU), 3211 Broughton Hall, Raleigh, NC 27695, United States
3. Oak Ridge National Laboratory (ORNL), One bethel Valley Road, Oak Ridge, TN 37932, United States
4. University of Bremen, Institute of Solid State Physics, P.O. Box 330440, Bremen 28334, Germany


Intrinsic stresses due to lattice mismatch and high densities of threading dislocations and extrinsic stresses resulting from the mismatch in the coefficients of thermal expansion are present in almost all III-Nitride heterostructures. Stress relaxation in the GaN layers occurs in conventional, cantilever (CE) and in pendeo-epitaxial (PE) films via the formation of additional misfit dislocations, domain boundaries, elastic strain and wing tilt. Polychromatic X-ray microdiffraction, high resolution monochromatic X-ray diffraction and finite element simulations have been used to determine the crystallographic properties, distribution of strain, dislocations, sub-boundaries and crystallographic wing tilt in uncoalesced and coalesced GaN layers grown by PE and CE. Tilt boundaries formed in the uncoalesced GaN layers at the column/wing interfaces essentially depend on the width-to-height ratio and growth conditions. Sharper tilt boundaries were observed at the interfaces formed by the coalescence of two laterally growing wings. The wings tilted upward during cooling to room temperature for both the uncoalesced and the coalesced GaN layers. It was determined that finite element simulations that account for extrinsic stress relaxation can explain the experimental results for uncoalesced GaN layers. Relaxation of both extrinsic and intrinsic stress components in the coalesced GaN layers contribute to the observed wing tilt and the formation of sub-boundaries.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium A, by Rozaliya I. Barabash
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-25 14:13
Revised:   2009-06-07 00:44
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