ABSTRACT

Strain effects in gallium nitride (GaN) layer grown on silicon (Si) (100) substrate are investigated. Results from Raman spectroscopy measurements suggested that the stress level in the GaN layer is around –0.48 GPa that is higher than several reported values. Moreover, the coherency of the GaN layer with respect to the Si substrate was confirmed by X-ray diffraction (XRD)-reciprocal space mapping XRDRSM measurement. As derived from XRD ω-rocking curve, the strain was around 0.0216 and –0.0241 along c-axis and a-axis, respectively. Meanwhile, results from temperaturedependent photoluminescence (PL) measurements indicated that the strain in the layer can be influenced by the binding energy of donors. In the effort to achieve strain reduction, few micrometres of the GaN layer were fabricated into porous structure. In particular, a sample was prepared without annealing treatment, and another was subjected to annealing treatment at 800°C prior to etching (pre-annealing). It was found that the strain was reduced with the porous structure, especially by the pre-annealing treatment.

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