Determination Of Critical Thickness In In x Ga 1-x As/GaAs Heterostructures By X-Ray Diffraction And Photoluminescence Measurements

Abstract

The critical thickness hc of strained InxGa1-x As/GaAs layers grown by molecular beam epitaxy (MBE) on GaAs (100) substrates is determined by double crystal x-ray diffraction and low-temperature photoluminescence measurements for 0.07 < x < 0.25. The x-ray rocking curves exhibit peaks from the InxGa1-xAs layer that are easily detectable at thicknesses as low as 100 A. The intensity of the photoluminescence peak is found to persist well beyond the experimentally determined critical thickness. Both techniques give essentially the same values of hc. The experimental results are compared with theoretical values of hc that are calculated from mechanical equilibrium and energy balance models. Good agreement is obtained between the results from the energy balance model and the experimental data.