Photoluminescence mapping and Rutherford backscattering spectrometry of InGaN epilayers

An experimental technique that provides an accurate measure of composition is necessary if we wish to ascertain the effect of indium content on the optical and structural characteristics of InGaN epilayers. Here we compare measurements by photoluminescence (PL) and Rutherford Backscattering Spectrometry (RBS) on two InGaN samples. The experimental results establish a direct linear relationship between the PL peak energy and the indium content. However, the indium fraction is not as high as might be expected for the low PL peak energies obtained in this work, probably in consequence of segregation in the InN-GaN solid solution. The samples also have relatively poor crystallinity. An excess of nitrogen, found in the sample of poorer quality, scales with PL peak energy.