Droplet epitaxy of semiconductor nanostructures for quantum photonic devices

Abstract

The long dreamed 'quantum internet' would consist of a network of quantum nodes (solid-state or atomic systems) linked by flying qubits, naturally based on photons, travelling over long distances at the speed of light, with negligible decoherence. A key component is a light source, able to provide single or entangled photon pairs. Among the different platforms, semiconductor quantum dots (QDs) are very attractive, as they can be integrated with other photonic and electronic components in miniaturized chips. In the early 1990s two approaches were developed to synthetize self-assembled epitaxial semiconductor QDs, or 'artificial atoms'-namely, the Stranski-Krastanov (SK) and the droplet epitaxy (DE) methods. Because of its robustness and simplicity, the SK method became the workhorse to achieve several breakthroughs in both fundamental and technological areas. The need for specific emission wavelengths or structural and optical properties has nevertheless motivated further research on the DE method and its more recent development, local droplet etching (LDE), as complementary routes to obtain high-quality semiconductor nanostructures. The recent reports on the generation of highly entangled photon pairs, combined with good photon indistinguishability, suggest that DE and LDE QDs may complement (and sometimes even outperform) conventional SK InGaAs QDs as quantum emitters. We present here a critical survey of the state of the art of DE and LDE, highlighting the advantages and weaknesses, the achievements and challenges that are still open, in view of applications in quantum communication and technology.

Next generation low temperature polycrystalline materials for above IC electronics. High mobility n- and p-type III–V metalorganic vapour phase epitaxy thin films on amorphous substrates

“…For this reason, we moved to a more complex approach. The method of choice was a multistep deposition process, following a droplet epitaxy-inspired protocol [12,13], where the group III precursor (normally TMGa, TEGa or TMIn) was injected into the reactor individually, and the resulting surface was then exposed to group V precursor (either AsH 3 or TMSb) for a period of time (minutes) to form crystalline 'seeds' for further, standard epitaxial overgrowth (with group III and V precursor injected simultaneously, see figure 1)…”

Low-noise GaAs quantum dots for quantum photonics

“…GaAs QDs in an AlGaAs matrix can be self-assembled by local droplet etching 8,9 and have a spectrally narrow ensemble 10,11 . They emit at wavelengths between 700 and 800 nm.…”

High‐Performance Broadband Tungsten Disulfide Photodetector Decorated with Indium Arsenide Nanoislands

“…Therefore, the In droplets on the surface of WS 2 follow the Volmer–Weber (VW) growth mode without the presence of a wetting layer (WL). [ 21,22 ] The subsequent step is the droplet crystallization by annealing in the group‐V As element atmosphere at 300 °C for 600 s. During this step, the As atoms impinge on the liquid metal droplets and are dissolved into them to form crystal InAs nanoislands. Figure 1b displays a typical atomic force microscopy (AFM) image of the as‐grown InAs nanoislands/WS 2 heterostructure.…”