Single InAs1−xPx/InP quantum dots as telecommunications-band photon sources

Abstract

The optical properties of single InAsP/InP quantum dots are investigated by spectrally-resolved and time-resolved photoluminescence measurements as a function of excitation power. In the shortwavelength region (below 1.45 µm), the spectra display sharp distinct peaks resulting from the discrete electron-hole states in the dots, while in the long-wavelength range (above 1.45 µm), these sharp peaks lie on a broad spectral background. In both regions, cascade emission observed by time-resolved photoluminescence confirms that the quantum dots possess discrete exciton and multiexciton states. Single photon emission is reported for the dots emitting at 1.3 µm through antibunching measurements. INTRODUCTIONThe three-dimensional confinement of electrons and holes in semiconductor quantum dots gives rise to discrete electron-hole states and sharp absorption and emission lines, analogous to those in atomic systems [1]. These features have been exploited to produce quantum states of light, such as single photons [2, 3], indistinguishable photons [4, 5, 40] and entangled photon pairs [7][8][9] that may be used in quantum communication protocols, such as quantum key distribution or quantum relays based on quantum teleportation [10][11][12][13]. At the same time, quantum dots have been used as gain media in photonic crystal nanolasers [14]. However, for highly-excited quantum dots placed inside photonic crystal nanocavities, it was found that the simple "artificial atom" model of the quantum dot, which successfully described the emission of one or two photons by the quantum dot in free space, could not adequately explain the emission of light by the dot into an apparently non-resonant nanocavity [15]. This cavity feeding required explicit consideration of multiply-excited states emitting into a broad quasicontinuum [16].To date most such photon sources and nanolasers have been fabricated with quantum dots embedded in a GaAs matrix and thus emitting around 920 nm, while prospective applications require sources operating in the telecommunications wavelength range, particularly in the Oand C-bands, around 1.3 µm and 1.5 µm respectively. InAs/InP quantum dots can emit in these wavelength bands and are well suited as active media in semiconductor optical amplifiers or ridge laser systems useful for telecommunications applications [17]. However, attempts to grow such dots by Molecular Beam Epitaxy (MBE) did not give the desired results, as growth on (001)-InP substrate generally leads to the formation of quantum dashes or quantum wires [18, 19], while growth on a (311)-InP oriented substrate [20] is not compatible with the standard processes used in the fabrication of photonic devices such as microcavities. Use of Metal-Organic Chemical Vapor Deposition (MOCVD), on the other hand, has made it possible to grow small InAsP/InP islands on a (100)-InP oriented substrate, as it allows for the spontaneous formation of a twodimensional wetting layer on which small islands can grow [21][22][23], while their spectral distribution [24] o...

Exciton and biexciton dynamics in single self-assembled InAs/InGaAlAs/InP quantum dash emitting near 1.55 μm

“…The s X ¼ 2:0 6 0:1 ns is longer than those obtained up to date for the InAsP/InP(001) (Ref. 22) or InAs/InP(001) (Refs. [23][24][25]28) QDs, which vary between 1.4 (Ref.…”

“…18 Since the third telecommunication window centered around 1.55 lm guarantees the lowest transmission losses and highest transmission rates, a true single quantum photon emitter at that wavelength is highly sought for. 19 Among already demonstrated solutions towards achieving single quantum emitter at 1.55 lm including PbS nanocrystals, 20 metamorphic InAs/(In,Ga)As self-assembled QDs, 21 InAsP/InP QDs, 22 InAs/InP QDs, 18,[23][24][25][26] and combined techniques using standard InAs/GaAs QDs and frequency down conversion, 27 the idea of utilizing the InAs/InP(001) QDashes 28 is still original and competitive.…”

“…28 Even for a more symmetric object, like InAs/InP(001) QD emitting near 1.55 lm, the information concerning single exciton and biexciton kinetics and emission statistics is limited. [22][23][24][25] In this Letter, we present experimental and theoretical studies of the exciton (X) and biexciton (XX) kinetics in a single selfassembled InAs QDash embedded in an In 0.53 Ga 0.23 Al 0.24 As matrix, lattice matched to an InP(001) substrate. The sample was grown in an EIKO gas source molecular-beam epitaxy system on an S-doped InP(001) substrate.…”

“…[23][24][25]28) QDs, which vary between 1.4 (Ref. 22) and 1.6-1.8 ns. [23][24][25]28 All values are reported for a single exciton decay in the wavelength emission range near 1.55 lm.…”

Photoluminescence lineshape and dynamics of localized excitonic transitions in InAsP epitaxial layers

“…However, while the morphology and the electronic properties of InAsP have been extensively explored, [7][8][9][10][11][14][15][16][17]31 studies concerning optical characterization are limited. [14][15][16][17] Although there are a large number of optical studies involving quantum structures, 2,[18][19][20] alloy epilayers are more appropriate when considering fundamental optical transitions since confounding effects, such as quantum confinement and interface-related defects, are avoided.…”