Recrystallization of epitaxial GaN under indentation

Authors :: Dhara, S.
Das, C. R.
Hsu, H. C.
Raj, Baldev
Bhaduri, A. K.
Chen, L. C.
Chen, K. H.
Albert, S. K.
Ray, Ayan
Source :: Appl. Phys. Lett. 92 (2008) 143114
Publication Year :: 2008
Abstract: We report recrystallization of epitaxial (epi-) GaN(0001) film under indentation.Hardness value is measured close to 10 GPa, using a Berkovich indenter. Pop-in burst in the loading line indicates nucleation of dislocations setting in plastic motion of lattice atoms under stress field for the recrystallization process. Micro-Raman studies are used to identify the recrystallization process. Raman area mapping indicates the crystallized region. Phonon mode corresponding to E2(high) close to 570 cm-1 in the as-grown epi-GaN is redshifted to stress free value close to 567 cm-1 in the indented region. Evolution of A1(TO) and E1(TO) phonon modes are also reported to signify the recrystallization process.<br />Comment: 10 pages, 3 figures