Threading dislocation reduction in heteroepitaxial GaSb based superlattices grown on silicon

Direct epitaxial growth of gallium antimonide (GaSb) on silicon (Si) holds the potential for creating new applications in mid-infrared (MIR) silicon photonics. However, this is challenging due to the significant physical dissimilarities between the two materials creating various crystal imperfections and defects. The main challenge is the generation of threading dislocations arising from the high lattice mismatch. To successfully implement GaSb-based devices on silicon a major engineering breakthrough is required to significantly reduce the dislocation density. This work presents a study of high quality GaSb epilayers on Si with defect density of 6 × 10⁶ cm^-2 grown using molecular beam epitaxy (MBE). This was achieved using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step GaSb growth temperature procedure and strained dislocation filter superlattices (DFSLs). The superlattice (SL) layers were carefully engineered and positioned to prevent the generation of new defects while blocking the vertical propagation of pre-existing ones. The successful reduction of the threading dislocations and excellent crystalline quality was identified through a significant increase of the photoluminescence intensity.