Efficient Emission in the Telecom Range from Quantum Dots Embedded in Photonic Structures Fabricated by Focused Ion Beam Milling

Abstract

In the present work, we focus on the development and optimization of the photonic structures fabrication with (In, Ga)As/GaAs quantum dots as an active part. Such structures offer the emission in the application-relevant range of the 2nd telecommunication window in view of obtaining efficient light collection, which is a critical requirement of practical, truly nonclassical sources for quantum communication schemes in fiber networks. We fabricated pillar-like photonic structures as a function of the sample and technological process parameters, which were then characterized by low-temperature micro-photoluminescence in order to optimize the emission intensity. We tested two different ion sources (Ga and Xe) also using an additional protection layer of carbon sputtered by the gas injection system. For each source, we have prepared a set of pillars with varying diameters and heights of the order of single micrometers, with fine-tuning of the beam currents and energy, and hence of the ion doses. We concluded that the optimized method should employ the xenon plasma focused ion beam technique, which takes advantage of high milling rate and high quality of etching of small structures, even micrometer in size, on the semiconductor material. For an optimized process, we obtained bright photoluminescence from single quantum dots. Our results indicate the potential of this technological approach employing xenon plasma focused ion beam technique to be suitable for the creation of photonic structures of good crystalline and optical quality, exhibiting efficient emission from embedded quantum dots in the telecommunication spectral range.