A comparative study of epitaxial InGaAsBi/InP structures using Rutherford Backscattering Spectrometry, X-ray diffraction and Photoluminescence techniques.

In this work we used a combination of photoluminescence (PL), high resolution X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) techniques to investigate material quality and structural properties of MBE-grown InGaAsBi samples (with and without an InGaAs cap layer) with targeted bismuth composition in the 3-4% range. XRD data showed that the InGaAsBi layers are more homogenous in the uncapped samples. For the capped samples, the growth of the InGaAs capped layer at higher temperature affects the quality of the InGaAsBi layer and bismuth distribution in the growth direction. Low temperature PL exhibited multiple emission peaks; the peak energies, widths and relative intensities were used for comparative analysis of the data in line with the XRD and RBS results. RBS data at random orientation together with channelled measurements allowed both an estimation of the bismuth composition as well as analysis of the structural properties. The RBS channelling showed evidence of higher strain due to possible anti-site defects in the capped samples grown at a higher temperature. It is also suggested that the growth of the capped layer at high temperature causes deterioration of the bismuth-layer quality. The RBS analysis demonstrated evidence of a reduction of homogeneity of uncapped InGaAsBi layers with increasing bismuth concentration. The uncapped higher bismuth concentration sample showed less defined channelling dips suggesting poorer crystal quality and clustering of bismuth on the sample surface.