Nano Express
Mechanical Deformation Behavior of Nonpolar GaN Thick Films by Berkovich Nanoindentation
1 Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, People’s Republic of China
2 Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, People’s Republic of China
Nanoscale Research Letters 2009, 4:753-757 doi:10.1007/s11671-009-9310-1
Published: 25 April 2009Abstract
In this study, the deformation mechanisms of nonpolar GaN thick films grown on m-sapphire
by hydride vapor phase epitaxy (HVPE) are investigated using nanoindentation with
a Berkovich indenter, cathodoluminescence (CL), and Raman microscopy. Results show
that nonpolar GaN is more susceptible to plastic deformation and has lower hardness
thanc-plane GaN. After indentation, lateral cracks emerge on the nonpolar GaN surface and
preferentially propagate parallel to the 
orientation due to anisotropic defect-related stresses. Moreover, the quenching of
CL luminescence can be observed to extend exclusively out from the center of the indentations
along the 
orientation, a trend which is consistent with the evolution of cracks. The recrystallization
process happens in the indented regions for the load of 500 mN. Raman area mapping
indicates that the distribution of strain field coincides well with the profile of
defect-expanded dark regions, while the enhanced compressive stress mainly concentrates
in the facets of the indentation.
