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Proceedings Paper

Understanding GaN nucleation layer evolution on sapphire and its impact on GaN dislocation density
Author(s): Daniel D. Koleske; Michael E. Coltrin; Stephen R. Lee; Gerald Thaler; Karen C. Cross; Michael J. Russell
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Paper Abstract

For improved GaN films on sapphire, GaN nucleation layers (NLs) are typically grown prior to high temperature growth. Using optical reflectance and AFM image analysis we have uncovered mechanistic details of GaN NL evolution during the ramp to high temperature. As the temperature is increased the NL decomposes and GaN nuclei form. We will demonstrate that the GaN nuclei are formed from gas phase Ga atoms generated during the NL decomposition which recombine with ambient NH3. Continued GaN growth on these nuclei results in GaN films with dislocation densities as low as 4x108 cm-2. We will show how the NL decomposition kinetics can be extracted from the optical reflectance waveforms and used to control the nuclei formation and growth. More recently we have investigated possible correlations between the GaN nucleation density and the resultant film dislocation density. We have initiated studies of ultra-low (< 107 cm-2) nucleation densities on sapphire using multi-step NL growth and annealing schemes. We find that over a wide range of nucleation densities that the nucleation density scales quadratically with the NL thickness. The dependence of the dislocation density on the nucleation density is currently being explored.

Paper Details

Date Published: 15 January 2008
PDF: 12 pages
Proc. SPIE 6841, Solid State Lighting and Solar Energy Technologies, 68410H (15 January 2008); doi: 10.1117/12.758766
Show Author Affiliations
Daniel D. Koleske, Sandia National Labs. (United States)
Michael E. Coltrin, Sandia National Labs. (United States)
Stephen R. Lee, Sandia National Labs. (United States)
Gerald Thaler, Sandia National Labs. (United States)
Karen C. Cross, Sandia National Labs. (United States)
Michael J. Russell, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 6841:
Solid State Lighting and Solar Energy Technologies
Jinmin Li; Yuwen Zhao; Nuofu Chen; Ling Wu; Yubo Fan; Vladimir M. Andreev; Yong-Hang Zhang; Jai Singh; Michael E. Coltrin, Editor(s)

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