Metamorphic Buffer Layer Platform for 1550 nm Single-Photon Sources Grown by MBE on (100) GaAs Substrate

Abstract

We demonstrate single-photon emission with a low probability of multiphoton events of 5% in the C-band of telecommunication spectral range of standard silica fibers from molecular beam epitaxy grown (100)-GaAs-based structure with InAs quantum dots (QDs) on a metamorphic buffer layer. For this purpose, we propose and implement graded In content digitally alloyed InGaAs metamorphic buffer layer with maximal In content of 42% and GaAs/AlAs distributed Bragg reflector underneath to enhance the extraction efficiency of QD emission. The fundamental limit of the emission rate for the investigated structures is 0.5 GHz based on an emission lifetime of 1.95 ns determined from time-resolved photoluminescence. We prove the relevance of a proposed technology platform for the realization of non-classical light sources in the context of fiber-based quantum communication applications.

Electronic and Optical Properties of InAs QDs Grown by MBE on InGaAs Metamorphic Buffer

“…High number of the observed emission lines is related to the relatively high surface density of QDs (~10 10 cm −2 ) [ 46 ], so without surface patterning the observation of single QDs is possible mainly in the tails of the entire emission band (using the advantage of the QD size distribution). Figure 9 b shows the excitation-power dependence (for full experimental data see Supplementary Materials : Figure S3 ) of the emission from single dots in a patterned structure (mesa diameter ~1 µm) in the spectral range of the second telecom window.…”

“…It was continued until the maximum value of the In content in the upper part of the MBL layer was reached. The graded InGaAs alloy acts as a substrate to grow optically-active InAs QDs red-shifted to the telecom range [ 46 ]. On top of the MBL, 1.5 monolayers of InAs material were deposited to form QDs.…”

“…To extend the spectral range of emission, it is necessary to apply additional steps to modify the properties of the dots, mostly employing the strain engineering or modification of the QDs’ size or composition [ 11 ]. There exist at least several approaches allowing for the shifting of the emission wavelength to the telecommunication windows, for instance by using vertically-stacked QDs [ 19 , 20 , 21 , 22 , 23 ], growth up to the second critical thickness [ 24 , 25 ], controlled overgrowth of InGaAs QDs [ 26 ], adding small concentrations of nitrogen to the InAs QDs [ 27 ], applying the strain-reducing layer [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], or the metamorphic-buffer-layer (MBL) [ 5 , 11 , 43 , 44 , 45 , 46 ]. Most of these solutions concern the use of QDs as an active region in lasers or amplifiers, while the practical demonstrations employing single GaAs-based QDs as an active element of non-classical emitters for quantum technology applications in the telecom range are still under development.…”

“…Most of these solutions concern the use of QDs as an active region in lasers or amplifiers, while the practical demonstrations employing single GaAs-based QDs as an active element of non-classical emitters for quantum technology applications in the telecom range are still under development. Furthermore, the only approach reported as suitable to obtain single-photon emission from InAs dots on the GaAs substrate in both the 2nd and 3rd telecommunication windows is the use of MBL and the related strain engineering [ 11 , 44 , 45 , 46 ]. Previous results concerned mainly MBL-based QD structures grown by metal-organic vapor-phase epitaxy (MOVPE) [ 45 ], which allowed for the demonstrating of important quantum communication milestones, such as the emission of indistinguishable photons [ 47 , 48 ]—also in the on-demand mode [ 49 ], generation of pairs of polarization-entangled photons [ 50 ], or the possibility of precise piezo-tuning [ 51 ].…”

“…Previous results concerned mainly MBL-based QD structures grown by metal-organic vapor-phase epitaxy (MOVPE) [ 45 ], which allowed for the demonstrating of important quantum communication milestones, such as the emission of indistinguishable photons [ 47 , 48 ]—also in the on-demand mode [ 49 ], generation of pairs of polarization-entangled photons [ 50 ], or the possibility of precise piezo-tuning [ 51 ]. For QDs grown by the molecular beam epitaxy (MBE), single-photon emission has been shown only in the third telecom window so far [ 46 ]. On the other hand, there are reports presenting the suitability of the MBL approach in the MBE growth of GaAs-based ensembles of QDs for laser applications in the telecom spectral range [ 43 , 52 ].…”