Robust Si3N4 masks for 100 nm selective area epitaxy of GaAs -based nanostructures

A robust shadow mask for fabrication of GaAs-based semiconductor nanostructures via selective area molecular beam epitaxy has been developed. The mask is based on a nano-patterned 100 nm thick Si3N4-membrane on a Si(100) support wafer. Into the membrane, holes with diameters down to 100 nm have been fabricated. The Si3N4-membranes have been produced by anisotropic etching of the Si(100) by KOH and the membrane itself is patterned by electron beam lithography and reactive ion etching. The masks are fully compatible with ultrahigh vacuum and the growth of (In,Ga,AI)As by molecular beam epitaxy. Test depositions of Ga show that one has to minimize the gap between substrate and mask and diffusion has to be suppressed to obtain a localized deposition governed by the hole diameter. Under optimized conditions we were able to deposite Ga in an area with 100 nm diameter.A GaAs layer, which is deposited on the front side of the mask, allows an in-situ hole size reduction and can be re-evaporated without damaging the mask. (C) 2017 Elsevier B.V. AU rights reserved.