Abstract
We report on comparative optical studies of InAs/Al0.44Ga0.56As quantum dots (QDs) grown by molecular beam epitaxy either with or without a thin GaAs interlayer inserted between the AlGaAs barrier and InAs QDs. Emission properties of individual QDs are investigated by micro-photoluminescence spectroscopy using 500-nm-size etched cylindric mesa structures. The single-photon statistics of the QDs of both types, emitting in the red spectral range between 636 and 750 nm, is confirmed by the measurements of the second-order correlation function. A negligibly small exciton fine structure splitting is detected in the majority of the QDs grown with the GaAs interlayer that implies the possibility of generating pairs of entangled photons with high entanglement fidelity.
Highlights
The development of quantum cryptography and linear optic quantum computations[1,2,3,4] relies on a nonclassical light source capable of emitting either a single photon or a pair of entangled single photons on demand at a defined frequency with high external quantum efficiency[5,6,7]
We expand the operational spectral range of the single-photon emitters fabricated in this system down to 636 nm, by means of InAs/AlGaAs Stranski-Krastanov quantum dots (QDs) fabricated by molecular beam epitaxy (MBE)[19,20,21,22]
We present comparative optical studies of InAs/Al0.44Ga0.56As QDs grown by MBE either with or without an ultra thin GaAs interlayer inserted between the bottom AlGaAs barrier and InAs QDs
Summary
The development of quantum cryptography and linear optic quantum computations[1,2,3,4] relies on a nonclassical light source capable of emitting either a single photon or a pair of entangled single photons on demand at a defined frequency with high external quantum efficiency[5,6,7]. Strain-induced QDs from a variety of different material systems, grown by the Stranski-Krastanov method, have been studied spectroscopically on a single QD level[9,10], including InAs/GaAs, InP/(Al,Ga,In)P, CdSe/Zn(S)Se, CdTe/ZnTe, and more recently (In,Ga)N/(Al,Ga)N11,12, InAs/InAlGaAsP13–15, and InAs/InGaAs16–18 All together, these systems allow fabrication of the single-photon emitters in an extended spectral range from middle ultraviolet to the optical telecommunication C-band (1.55 μm). We expand the operational spectral range of the single-photon emitters fabricated in this system down to 636 nm, by means of InAs/AlGaAs Stranski-Krastanov QDs fabricated by molecular beam epitaxy (MBE)[19,20,21,22] In these structures, the shift of the emission wavelength towards shorter wavelengths as compared with the most studied InAs/GaAs QDs arises from a combination of the larger barrier band gap and possible interdiffusion of Al into the QD material[20]. Details of the measurement techniques are described in the section Methods
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