Analysis of physical properties of III-nitride thin films by nanoindentation

The thin films of undoped GaN, GaN:Si, and Al0.12Ga0.88N on sapphire (0001) substrate using nanoindentation are investigated. The Young's modulus, hardness, and plastic energy of the films were calculated from the loading-unloading curve. The true hardness, maximum shear stress, and degree of elastic recovery are then deduced from the preceding calculated data. In addition, the loading-unloading curve clearly shows the pop-in phenomena, which can be attributed to the dislocation nucleation. To better understand the factors affecting the quality of films produced, the stress-strain relationship, which is able to reflect the quality of the fabricated films, is also analyzed using nanoindentation.