Nanoindentation of Mg-doped AlGaN thin films

• Mg-doped AlGaN thin films are deposited on sapphire substrates by MOCVD.
• Hardness and Young’s modulus of Mg-doped AlGaN films are measured by nanoindentation.
• Pop-ins are observed in Mg-doped AlGaN films in the load–displacement curves.

The effects of Mg-containing precursor flow rate on the nanomechanical characteristics of the Mg-doped AlGaN thin films are investigated by using nanoindentation technique. The Mg-doped AlGaN thin films were deposited on sapphire substrates by metal–organic chemical–vapor deposition (MOCVD) with the various flow rates of 100, 200 and 600 sccm of bis-(cyclopentadienyl)-magnesium (Cp2Mg) precursor. Nanoindentation results revealed apparent discontinuities (so-called multiple “pop-ins”) in the load–displacement curves, while no discontinuity was observed in the unloading segment of the load–displacement curves. The hardness and Young’s modulus of Mg-doped AlGaN thin films measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) method indicated that both mechanical properties increased with increasing the Mg concentration with the hardness and the Young’s modulus being increased from 20.62 ± 0.53 to 24.17 ± 0.72 GPa and from 317.48 ± 7.82 to 364.63 ± 17.62 GPa, respectively, as the Mg concentration raised from 100 to 600 sccm.

The Mg concentrations of p-AlGaN thin films at a depth of 200 nm are 5.5 × 1019, 1.8 × 1019 and 1.5 × 1019 atom/cm3, corresponding to the Mg flow rate of 600, 200 and 100 sccm.The Mg-doped AlGaN thin films also exhibited clear evidences of the multiple “pop-ins” in the load–displacement curves during nanoindentation. Moreover, the first pop-in event is slightly increased with increasing the Mg concentrations.Figure optionsDownload as PowerPoint slide