Xenon-plasma focused ion beam processing of photonic microstructures with GaAs-based quantum dots

Abstract

So far, successful focused ion beam (FIB) based fabrication of photonic structures with quantum dots (QDs) has been limited to cases with above 1 µm thick cap, usually in a form of a distributed Bragg reflector of a vertical cavity, which simultaneously protects the active region from the destructive influence of the ion beam. Here, we propose optimized xenon-plasma FIB (Xe-PFIB) technology as a fast and cost-efficient solution alternative to the commonly used combination of electron beam lithography and etching. We demonstrate a 3D processing of GaAs-based photonic microstructures with InGaAs QDs emitting close to the telecom O-band for cylindrical mesas with different cap thicknesses (50-650 nm) obtained by using two approaches: (i) Xe-PFIB for both reducing the cap thickness as well as the in-plane microstructure size, and (ii) wet chemical etching for cap layer removal and subsequent Xe-PFIB for the in-plane milling. The latter appeared more efficient when judging by photoluminescence intensity. Utilizing an additional protecting layer of platinum or carbon was also tested. Eventually, we for the first time show successful FIB-based fabrication of photonic microstructures with bright emission from single QDs capped with only 200 nm layer, which indicates the prospects of this technology for processing of efficient QD-based single-photon sources for quantum communication.