Nanoindentation on AlGaN thin films

Hardness and Young's modulus were measured in AlGaN thin films with differe nt Al content, using a nanoindentation technique. Hardness slightly decreas es with increasing Al content, ranging from 20.2 to 19.5 GPa for Al content from 0.09 to 0.27, respectively. No significant variations of Young's modu lus were observed. The resulting value of Young's modulus is 375 GPa. Disco ntinuities in load-displacement curves were found, which are associated wit h dislocation nucleation. The threshold load for this discontinuity depends on the conditions of the nanoindentation test. Below the threshold load, t he sample surface flexes elastically in response to the indenter contact an d the displacements recover completely when the sample is unloaded. (C) 199 9 American Institute of Physics. [S0021-8979(99)06224-6].