Strain relief and threading dislocation reduction in GaSb/AlSb/GaSb heterostructures grown on Si(001) substrate

The monolithic integration of III-Sb materials on Si substrates enables the development of novel functionalities and promising device applications. However, due to the large lattice mismatch to Si, direct heteroepitaxy of III-Sb results in a very large and disadvantageous dislocation density. Here, we report on the effect of strained AlSb interlayers in GaSb as dislocation filters for the epitaxy on Si(001) substrates. The epitaxial stress introduced by the lattice mismatched AlSb layer leads to threading dislocation bending at the interfaces as a strain relieving mechanism, thereby facilitating the reaction and annihilation of dislocations during their lateral glide process. Using comprehensive electron channeling contrast imaging and scanning transmission electron microscopy, we measure the dislocation density at the surface and after filter and cap layers of different thicknesses and analyze the effect of plastic strain relaxation on dislocation reduction. The reduction mechanism is discussed in the context of misfit dislocation networks forming at the respective compressively and tensile strained interfaces. With the new findings, an effective double filter layer structure with adopted layer thicknesses could be realized, which has resulted in a very low threading dislocation density of 1.7×107cm−2.