Chemical composition of In xGa 1− xAs epilayers grown simultaneously on differently oriented GaAs substrates

Abstract

We investigate the In-composition of In x Ga 1− x As ternary layers epitaxially grown by molecular beam epitaxy. The epilayers of different indium content (mole fraction 0.2< x<1) are grown simultaneously onto GaAs substrates of different crystallographic orientation, namely (0 0 1), (1 1 1)B and (1 1 3)A surfaces. High-resolution X-ray diffraction, electron probe microanalysis, energy-dispersive X-ray spectroscopy and scanning electron microscopy measurements show that for a suitable set of parameters high-quality In x Ga 1− x As layers can be simultaneously grown by MBE on differently oriented GaAs substrates. Secondary ion mass spectrometry measurements show that the In-incorporation is constant over the whole layer thickness and for all surface orientations. In addition, the epilayers grown during the same run have the same chemical composition independent from the substrate surface orientation. Moreover, a comparison of the InAs mole fractions obtained by X-ray diffraction and electron probe microanalysis confirms the validity of Vegard's rule for the In x Ga 1− x As lattice parameter and the Poisson's ratio within 0.5% of the experimental accuracy.