Design of InxGa1−xAs buffer layers for epitaxial growth of high-quality In0.3Ga0.7As films on GaAs substrates

Abstract

A phase field model is developed to simulate In_0.3Ga_0.7As thin films grown on an GaAs substrate with different buffer layer structures. Using this newly developed phase field model, an optimal step graded In_xGa_1−xAs buffer layer structure with four sub-layers of x = 0.09, 0.18, 0.27, and 0.33 is then proposed for epitaxial growth of high-quality In_0.3Ga_0.7As film on GaAs substrate. The strain distribution analysis by using the phase field model reveals that the compressive strain in this optimal heterostructure is partially balanced by the tensile strain caused by the uppermost two layers of In_0.3Ga_0.7As grown on top of In_0.33Ga_0.67As, which results in high-quality In_0.3Ga_0.7As film. The subsequent epitaxial growth of In_0.3Ga_0.7As films on GaAs substrates demonstrates that the surface RMS roughness and the full width at half maximum of X-ray rocking curve of as-grown In_0.3Ga_0.7As film with the optimal buffer layer structure are as low as 0.56 nm and 116′′, respectively, indicating very high film quality. These experimental results confirm the high effectiveness of the proposed approach to design buffer layer structure using our newly developed phase field model. This phase field model should be able to extend to hetero-epitaxial growth of other material systems apart from InGaAs.