Nanotemplate-directed InGaAs/GaAs single quantum dots: Toward addressable single photon emitter arrays

Abstract

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Mesa-top quantum dot single photon emitter arrays: Growth, optical characteristics, and the simulated optical response of integrated dielectric nanoantenna-waveguide systems

“…Details of the substrate patterning, growth conditions, and grown structure can be found in ref. 24. The single photon emission results reported here are from a 5x8 array of flat-top pyramidal MTSQDs with {103} side planes ( Fig.3(b)) formed with 4.25 ML In 0.5 Ga 0.5 As deposited on size-reduced GaAs(001) mesa tops with as-etched nanomesa size of ~430 nm.…”

“…It is important to note that growth on mesatop, unlike in recess, enables accommodation of large lattice mismatch strain without generation of defects owing to the mesa free surfaces during growth and is thus suitable for a wide variety of material combinations covering optical emission from the UV (such as in the III-Nitrides) to the midinfrared (such as in the small bandgap InSb). The SESRE quantum dots reported here exploit the shallow {103} sidewalls 24 . Finally, we note that SESRE not only permits control on mesa-top SQD shape and size, it also allows controlled vertical stacking and coupling of QDs, as desired 31,32 .…”

“…Subsequent heteroepitaxy, lattice matched or mismatched, then enables synthesis of quantum confined nanostructures such as quantum wires and dots on pristine nanotemplates 23 . For the technologically important (001) surface oriented substrates of the tetrahedrally-bonded semiconductors of groups IV, III-V, and II-VI, the <100> edge orientations of square mesas provide four-fold symmetry and thus potentially symmetric migration of adatoms from the sidewalls to the top (Fig.3a) to reduce, in-situ, the as-patterned mesa top size to the desired size utilizing homoepitaxy under controlled growth kinetics 23,24,[31][32][33] . Indeed, depending upon the chosen as-etched sidewall crystallographic planes, the size-reducing growth can offer more than one pinch-off stages 33 , thereby allowing control on not only size but also the shape of the QD formed subsequently via heteroepitaxy as depicted in Fig.3 , both synthesized using solid-source molecular beam epitaxy (SSMBE).…”

“…For the SPS array, we report on the fabrication and optical characterization of spatially-ordered and spectrally-uniform SPS 5x8 array (Fig.1a) based on GaAs(001)/InGaAs/GaAs SQD residing on nanomesa tops synthesized through the approach of substrate-encoded size-reducing epitaxy (SESRE) 23,24,25 that naturally lends itself to on-chip integration with light manipulation units. The array exhibits an average g (2) (0) of 0.19±0.03 at 8 K reflecting good quantum confinement.…”

“…2 serve as the basic units which, appropriately interconnected, will enable the next level of hierarchical design enabling SQD-SQD communication, and thus the creation of optical circuits ( Substrate-encoded size-reducing epitaxy 23 is an approach to growth-controlled spatially-selective formation of nanostructures that exploits growth on designed non-planar patterned substrates, i.e. patterned structurally such that the tailored surface curvature induces surface stress gradients (capillarity) that direct adatoms during deposition preferentially to mesa tops [23][24][31][32][33][34][35] or valleys 23,36 / recesses 37,38 for selective incorporation through control on the relative kinetics of adatom incorporation on the contiguous facets present in the designed curvature 23,[31][32][33][34][35] . For pattern designs that induce net migration from the side facets to the mesa top, preferential incorporation at the mesa-top leads to growth-controlled mesa size reduction, enabling in-situ preparation of contamination and defect-free nanomesa arrays from the as-patterned array via homoepitaxy.…”