Photonic crystal nanocavities in GaAs/AlGaAs with oxidised bottom cladding

We present a solution to the difficult task of removing an oxide-based hard mask from a photonic crystal fabricated in the GaAs/AlGaAs system. We use a polymer backfill technique to seal the AlGaAs layer, thereby making it inaccessible to the wet-etch solution. This allows us to use a GaAs active layer for the photonic crystal placed on an oxidised AlGaAs layer which provides mechanical and thermal support. Using this technique, we fabricated GaAs-based photonic crystal cavities and measured respectable quality factors (Q ≈ 2200) despite the intrinsic asymmetry of the system. The technique presents a viable method for producing electrically injected photonic crystal cavities for operation on a mechanically stable and thermally conducting buffer layer.

► Novel and innovative fabrication of photonic crystal nanocavities with oxidised bottom cladding.
► Etching is achieved through a hard mask, which is removed without desolving the AlGaAs.
► Protection of AlGaAs is achieved by a polymer backfill that blocks the access of the wet etchant to the AlGaAs.
► Respectable quality factors of up to 2200 were achieved, which are the highest reported in these type of systems.