Quality-enhanced In_(0.3)Ga_(0.7)As film grown on GaAs substrate with an ultrathin amorphous In_(0.6)Ga_(0.4)As buffer layer

摘要

Using low-temperature molecular beam epitaxy, amorphous In_(0.6)Ga_(0.4)As layers have been grown on GaAs substrates to act as buffer layers for the subsequent epitaxial growth of In_(0.3)Ga_(0.7)As films. It is revealed that the crystallinity of as-grown In_(0.3)Ga_(0.7)As films is strongly affected by the thickness of the large-mismatched amorphous In_(0.6)Ga_(0.4)As buffer layer. Given an optimized thickness of 2 nm, this amorphous In_(0.6)Ga_(0.4)As buffer layer can efficiently release the misfit strain between the In_(0.3)Ga_(0.7)As epi-layer and the GaAs substrate, trap the threading and misfit dislocations from propagating to the following In_(0.3)Ga_(0.7)As epi-layer, and reduce the surface fluctuation of the as-grown In_(0.3)Ga_(0.7)As, leading to a high-quality In_(0.3)Ga_(0.7)As film with competitive crystallinity to that grown on GaAs substrate using compositionally graded In_xGa_(1-x)As metamorphic buffer layers. Considering the complexity of the application of the conventional In_xGa_(1-x)As graded buffer layers, this work demonstrates a much simpler approach to achieve high-quality In_(0.3)Ga_(0.7)As film on GaAs substrate and, therefore, is of huge potential for the InGaAs-based high-efficiency photovoltaic industry.