Depth profiles of lattice disorder in GaN irradiated with ions are bimodal: damage accumulates both in the crystal bulk and at the surface. The damage buildup near the surface proceeds as layer-by-layer amorphization originating at the surface, while the position of the disorder maximum in the bulk shifts deeper into the target with increasing ion dose starting at the depth corresponding to the maximum of elastic energy losses. In addition, the relative concentration of stable damage in this peak exhibits saturation at ~ 40−50% in many cases. Physical nature of such damage buildup behavior is still not understood. Here, we consider a physical model that can explain such a behavior of the damage accumulation in the bulk of GaN for cases when the amorphous/crystalline interface is close to the region of the primary mobile point defect formation.

Basing on the assumption that the amorphous/crystalline GaN interface is a strong sink for mobile point defects, we suppose that two reasons can be responsible for such a behavior: shift of this interface deeper into the bulk and increase of diffusion length during ion dose accumulation. Computer simulation based on these assumptions shows a good qualitative agreement with experimental results.

Work in St. Petersburg was supported by RFFI (grants 08-08-00585 and 09-08-92657). Work at LLNL was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Andrei Titov, State Polytechnic University, St. Petersburg 195251, Russia, Russian Federation
Platon Karaseov, State Polytechnic University, St. Petersburg 195251, Russian Federation
Alexander Azarov*, Department of Physics, University of Oslo, PO Box 1048 Blindern, NO-0316 Oslo, Norway, Norway
A. Kataev, State Polytechnic University, St. Petersburg 195251, Russian Federation
Sergei Kucheyev, Lawrence Livermore National Laboratory, Livermore, California 94551, U.S.A., United States

*presenting author