Influence of Mg-containing precursor flow rate on the structural, electrical and mechanical properties of Mg-doped GaN thin films

The effects of Mg-containing precursor flow rate on the characteristics of the Mg-doped GaN (GaN:Mg) were systematically studied in this study. The GaN:Mg films were deposited on sapphire substrates by metal-organic chemical-vapor deposition (MOCVD) with various flow rates of 25, 50, 75 and 100 sccm of bis-(cyclopentadienyl)-magnesium (Cp2Mg) precursor. The structural, electrical and nanomechanical properties of GaN:Mg thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Hall measurement and nanoindentation techniques, respectively. Results indicated that GaN:Mg films obtained with 25 sccm Cp2Mg possess the highest hole concentration of 3.1 × 1017 cm−3. Moreover, the hardness and Young's modulus of GaN:Mg films measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option showed positive dependence with increasing flow rate of Cp2Mg precursor, presumably due to the solution hardening effect of Mg-doping.

Fig. (a) shows the SIMS depth profile analyses revealing the actual Mg atomic concentration in GaN:Mg thin films grown by the present low pressure growth technique. It is evident that the Mg concentration remains rather uniform throughout the entire thickness of GaN:Mg thin film. Fig. (b) displays the SIMS analysis of H concentration in GaN:Mg thin films. It can be observed that the H concentration is slightly increased with increasing Mg flow rate. The results indicate that there is intimate correlations between the increased hole concentration and the decreased H concentration in GaN:Mg thin films.Figure optionsDownload as PowerPoint slideHighlights
► The GaN:Mg thin films are grown by MOCVD.
► Electrical properties of GaN:Mg thin films are measured by Hall measurement.
► Hardness and Young's modulus of GaN:Mg thin films are measured by nanoindentation.