The nanomechanical characteristics of Mg-doped GaN (GaN:Mg) thin films deposited on sapphire substrates were investigated by nanoindentation evaluation. The concentration of Mg in the GaN:Mg thin films was controlled by varying the flow rate of the bis (cyclopentadienyl) magnesium (Cp 2Mg) precursor during the metal-organic chemical vapor deposition (MOCVD) process. Apparent discontinuity in the load-displacement curve (the so-called "pop-in" event) featuring the homogeneous nucleation of dislocations was observed during the loading cycle of nanoindentation tests. Moreover, the loading at which the pop-in takes place appears to increase with increasing Mg-doping. The hardness and Young's modulus of the GaN:Mg thin films obtained by operating the Berkovich nanoindenter with the continuous contact stiffness measurements (CSM) mode also respectively increased from 20.4 GPa and 317.6 GPa to 26.2 GPa and 377.5 GPa for films obtained by increasing the flow rate of Cp 2Mg from 25 to 100 sccm, corresponding to Mg concentration of 4.54× 1018 atom/cm3 to 1.14×1020 atom/cm3 as revealed by secondary ion mass spectroscopy.
- GaN:Mg thin films
- Maximum shear stress