Simultaneous determination of Poisson ratio, bulk lattice constant, and composition of ternary compounds: In0.3Ga0.7As, In0.3Al0.7As, In0.7Ga0.3P, and In0.7Al0.3P

A technique using the common (004) x-ray diffraction spectrum is demonstrated for the simultaneous determination of Poisson ratio, bulk lattice constant, and alloy composition for ternary compounds with lattice constants near the midpoint between GaAs and InP. Thin, strained layers of InGaAs, InAlAs, InGaP, and InAlP were grown. By careful choice of ternary composition and thickness, the same composition was grown on both GaAs and InP substrates without measurable relaxation in the (004) x-ray spectrum. The diffraction equation was simultaneously solved for the Poisson ratio and bulk lattice constant of the ternary compound. Subsequently the ternary composition was determined by applying Vegard’s law. The resulting Poisson ratios agreed well with the compositional averages of the binary endpoints. By extrapolating the results for InAlAs, a Poisson ratio of 0.33 was determined for AlAs.