Defect reduction in GaSb nano-ridges on (001) Si substrates

Abstract

Nano-ridge engineering (NRE) is a unique approach for the direct heteroepitaxial growth of III-V materials on 300 mm Si substrates. It builds upon selective area growth and aspect ratio trapping of misfit defects by depositing in high-aspect ratio trenches while innovating in its ability to increase the defect-free III-V volume via the growth out of the trenches, giving rise to large nano-ridges (NR). NRE was already successfully applied for the demonstration of electrically injected GaAs NR lasers fully processed in a CMOS prototyping line. The introduction of GaSb to the "NRE toolkit" would allow to further extend the emission wavelength. GaSb NRs where established in a previous study using either a thin GaAs or InAs seed layer on Si before switching to GaSb growth (Baryshnikova et al., 2020). Unfortunately, the choice of GaAs resulted in a low threading dislocation density (TDD) but high planar defect density (PDD) whereas the application of an InAs seed showed the opposite behaviour. Here, a GaSb seed was explored with the aim of lowering both defect types simultaneously. Studying different GaSb seed growth conditions, the same correlation between the presence of either a high PDD along with a low TDD or vice versa was observed. To improve upon both defect types at the same time, the application of an InGaSb seed (10-15% In) was investigated. The ternary seed allowed to enhance the nucleation of strain releasing misfit defects at the III-V/Si interface compared to the binary GaSb seed. This improvement reduces the risk of strain built-up during further GaSb growth, thereby avoiding new defect formation. Finally, the InGaSb seed enabled us to demonstrate GaSb NRs with record low TDD (similar to 1.105 cm-2) and PDD (similar to 0.1 mu m-1) in 400 nm high NRs.