Local droplet etching with In, Al and InAl in In0.52Al0.48As layers for generation of quantum dots emitting in the optical C-band

We present a detailed study of local droplet etching into In 0.52 Al 0.48 As layers grown lattice matched on InP (100) substrate. We tested droplet etching with Ga, In, Al, InGa and InAl droplets under an As 2 atmosphere. Ga and InGa droplets did not produce proper nanoholes whereas we could produce nanoholes with In, Al, and InAl as etching material. Interestingly we found that the process required an additional overgrowth step when In is involved in combination with As 2 to prevent nanohole collapse after formation. We also optimized nanohole etching for symmetric QD fabrication when employing InAl as droplet material by investigating the influence of As 2 pressure and etching material amount under a fixed etching temperature of 435 °C. By doing this we found that 2 × 10 -7 mbar of As 2 flux and 1.4 ML at 435 °C produces nanoholes with favorable morphologies for future fabrication of symmetric quantum dots with average heights of (33.2 ± 2.5) nm in growth direction. These parameters worked well for all three etchants that we tested. In addition, we looked at the changes in depth, diameter, ring height and density of the nanoholes when varying the etching temperature between 410 and 505 °C for nanoholes etched with In, Al and InAl at 2 × 10 -7 mbar of As 2 flux and 1.4 ML droplet deposition. • Droplet etched nanoholes degrade under As 2 atmosphere when In is utilized as an etchant. However, the nanoholes can be conserved by an additional overgrowth step directly after the etching process. • The influence of residual As 2 pressure and deposition amount was systematically tested for InAl deposition at a fixed etching temperature of T e t c h = 435 ∘ C and etching time of 3 min. • Nanoholes etched with InAl at an etching temperature of T e t c h = 435 ∘ C , residual As 2 pressure of 2 × 10 -7 mbar and deposition amount of 1.4 ML are showing favorable in-plane symmetry for further quantum dot fabrication with hole depths of (33.2 ± 2.5) nm. • Lastly the effect of etching material was tested for In, Al and InAl at etching temperatures between 410 and 505 °C at a fixed residual As 2 pressure of 2 × 10 -7 mbar and etching material amount of 1.4 ML.