Temperature-dependent properties of single long-wavelength InGaAs quantum dots embedded in a strain reducing layer

Abstract

We report on temperature-dependent investigations of single metal-organic vapor phase epitaxy-grown In(Ga)As/GaAs quantum dots at wavelengths above 1 μm. Here, two types of samples are compared, whereas the quantum dots differ in the material composition and are embedded in a strain reducing layer to achieve an emission redshift. The analysis is performed by standard micro-photoluminescence spectroscopy, time-correlated photon counting, and intensity second-order autocorrelation measurements. It is found that the long-wavelength quantum dots experience a high charge carrier confinement (∼200 meV), but the thermal emission of carriers into the barrier or the wetting layer is mainly dominated by the shell spacing of individual dots. Additionally, we demonstrate that the single-dot carrier dynamics is reservoir-dominated. The influence of the strain reducing layers seems to cause this effect, leading to changes in the effective dot filling rate and charge configuration. Single-photon emission is preserved up to 77 K for a sample spectrally reaching the telecom O-band and then allowing for quantum dot single-photon operation at liquid nitrogen temperatures.

Thermal stability of emission from single InGaAs/GaAs quantum dots at the telecom O-band

“…2 c). The temperature dependence of µPL intensity I(T) can be described by 36 : where I 0 , I P are initial and reservoir-gained intensities, E 1 , E 2 are activation energies of processes responsible for increase, decrease of emission intensity, respectively, and B 1 , B 2 are the amplitudes of thermally-activated processes with energies E 1 and E 2 . In the case of charged complexes, a distinct temperature interplay of their relative intensities was observed in the low temperature range: the activation energy E 1 ≅ 1.9 meV was assigned to the pronounced μPL intensity increase of X + at temperatures up to 30 K. This energy is characteristic also for X − µPL intensity reduction indicating thermal activation of positive carrier traps (i.e.…”

Optical Quality of InAs/InP Quantum Dots on Distributed Bragg Reflector Emitting at 3rd Telecom Window Grown by Molecular Beam Epitaxy

“…Developing efficient non-classical light sources operating at room temperature and compatible with telecommunication windows is the holy grail of quantum communication and quantum information processing [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. The room temperature operation can be realized in many physical systems [ 6 ], including quantum dots (QDs), e.g., GaN-based [ 9 , 10 ], color centers in diamond [ 11 , 12 , 13 ], defects in SiC [ 14 ] or carbon nanotubes [ 15 , 16 ], atoms [ 17 ], as well as attenuated lasers [ 18 ] and sources relying on the parametric-down conversion process [ 19 , 20 , 21 ].…”

“…The key figures of merit for non-classical light sources are, e.g., single-photon purity, photon indistinguishability, and the number of mutually entangled photons. Epitaxial QDs hold performance records in this regards [ 1 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. These are inherently quantum emitters (with non-classical emission statistics) that have been proven to constitute nearly ideal single-photon sources at emission wavelengths below 1 μm [ 4 , 8 , 38 , 39 , 40 ].…”

Bright Purcell enhanced single-photon source in the telecom O-band based on a quantum dot in a circular Bragg grating

“…An expected red-shift of the emission line of around 3 nm is observed. 48 With a combined count rate of 262 kcps on the detectors, a g (2) (0) of 0.026 ± 0.001 is obtained (Figure 5b). Further increasing the temperature to 77 K results in an additional red-shift and line broadening (Figure 5c).…”

“…As higher temperatures lead to a phonon broadening of the emission line, the spectral selection window is increased to FWHM = 0.1 nm to avoid spectral filtering with a width smaller than the zero-phonon line. 48 To verify that this is not the case for the approach for the previous measurements at 4 K with the smaller spectral selection window of 0.04 nm, the corresponding measurement are repeated using the larger spectral selection window. The absence of a significant degradation regarding the detected count rate as well as g (2) (0) confirms that at 4 K the FWHM of the emission line is much smaller than the spectral selection window.…”