Nanoindentation on AlGaN thin films

Hardness and Young's modulus were measured in AlGaN thin films with different Al content, using a nanoindentation technique. Hardness slightly decreases 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 modulus were observed. The resulting value of Young's modulus is 375 GPa. Discontinuities in load-displacement curves were found, which are associated with dislocation nucleation. The threshold load for this discontinuity depends on the conditions of the nanoindentation test. Below the threshold load, the sample surface flexes elastically in response to the indenter contact and the displacements recover completely when the sample is unloaded. (C) 1999 American Institute of Physics. [S0021-8979(99)06224-6].