Micro-Raman analysis of molar fraction in polycrystalline Inx Ga1-x for traveling liquidus zone growth method

In_xGa_1-xAs is a tunable lattice matched bulk substrate material for fabricating InGaAs-based optoelectronic devices. Spatial homogeneity in molar fraction for such substrates is essential. It is planned to grow compositionally homogeneous In_xGa_1-xAs bulk substrate using In_xGa _1-xAs polycrystals with graded molar fraction profile as the starting material in the traveling liquidus zone growth method. To analyze these starting materials, particularly the molar fraction, non-destructive techniques are essential. In this paper, we report some results on micro-Raman studies in these polycrystalline starting materials with various values of molar fraction, and a polycrystalline In_xGa_1-xAs cylindrical sample with graded molar fraction profile. Estimated molar fraction using Raman scattering for various polycrystalline samples show good agreements with those examined by chemical analysis. We further report the effect of surface condition on our results, using micro-Raman technique