Site-controlled quantum dots fabricated using an atomic-force microscope assisted technique

Abstract

An atomic-force microscope assisted technique is developed to control the position and size of self-assembled semiconductor quantum dots (QDs). Presently, the site precision is as good as ± 1.5 nm and the size fluctuation is within ± 5% with the minimum controllable lateral diameter of 20 nm. With the ability of producing tightly packed and differently sized QDs, sophisticated QD arrays can be controllably fabricated for the application in quantum computing. The optical quality of such site-controlled QDs is found comparable to some conventionally self-assembled semiconductor QDs. The single dot photoluminescence of sitecontrolled InAs/InP QDs is studied in detail, presenting the prospect to utilize them in quantum communication as precisely controlled single photon emitters working at telecommunication bands.

Self-assembled InAs quantum dot formation on GaAs ring-like nanostructure templates

“…Because of the need to control the size, shape, and distribution of these zero-dimensional structures, much effort has been put forth to fabricate QDs with uniformity and precision. Different methods have attempted to fulfill this task, including chemical synthesis [8], lithography [9][10][11], STM and AFM tip-assisted deposition [12,13], and self-assembly [14][15][16][17][18]. The growth of unique complex structures such as rings, ensembles of dots, and molecules have been successfully demonstrated [16,19,20].…”

Advanced Technologies for Quantum Photonic Devices Based on Epitaxial Quantum Dots

“…To achieve a small FSS (smaller than the homogeneous emission linewidth), as required for reproducible polarization‐entangled photon pair generation, fine control of the droplet in‐plane anisotropy is necessary. Symmetric QDs grown along the crystal axis, which has C 3v crystal symmetry, has been theoretically predicted, and experimentally demonstrated . Indeed, strain‐free GaAs/AlGaAs QDs grown by DE on GaAs (111)A surface have been shown to yield polarization‐entangled photons with fidelity up to 0.86 ± 0.02 .…”

“…For example, nanoholes patterned on a flat (001) substrate surface define preferential QD nucleation positions, associated with surface chemical potential minima, at the bottom of each nanohole. Different lithographic techniques have been demonstrated for the fabrication of patterned substrates, including e‐beam lithography, nanoimprint lithography, focused ion beam (FIB) patterning, and atomic force microscopy (AFM) oxidation lithography . Typical results of patterned InAs dots using e‐beam lithography are shown in Figure a–d.…”

Kinetic Monte Carlo simulation of site-controlled GaAs/AlGaAs QDs growth on structured substrate

“…The achievement of site-controlled QDs or QD molecules has always presented a challenge due to the stochastic nature of self-assembled growth. A variety of schemes to control the nucleation locations of the dots have been examined, ranging from standard lithographic techniques to atomic force lithography [5][6][7]. The fabrication of structured substrate templates is an important technique for obtaining site-controlled quantum nanostructures based on the control of QDs nucleation sites [8][9][10][11].…”