Self assembled InAs/GaAs Quantum Dots (QD) have received much interest both from the standpoint of fundamental physics and technological applications. In consequence, thanks to these nanostructures important advances in optoelectronics and quantum technologies have been achieved [1]. However, these QDs have also some disadvantages, concerning to a strong decrease of the emission intensity with the temperature or difficulties to obtain emission wavelengths beyond 1 ?m, when they are grown on GaAs substrates [2]. In this work we show an original approach to grow by Molecular Beam Epitaxy (MBE) long wavelength emitting metamorphic InAs/InGaAs/ GaAs QDs, with high single nanostructure optical quality [3]. Subcritical InAs coverages allow to obtain low QD density (108 cm-2) and the reduction of QD strain and confining potential provided by the metamorphic InxGa1-xAs confining layer results in emission wavelengths at 1.3 ?m. For this purpose, two samples with different Indium compositions have been studied (x=0.15, 0.30). At low excitation power the micro-Photoluminescence (?PL) spectra show emission lines characteristic of a single QD. Figure 1a shows ?PL spectra from a single QD emitting at around 1171 nm in a sample with x = 0.15. The spectra show typical excitonic (Xn) and biexcitonic (XXn) lines, which can be identified studying the integrated intensity power dependence and the selective optical pumping effect associated to local unintentional impurities [4]. In sample with x = 0.30 (Figure 1b) it was observed excitonic emission around 1.336 µm (second window of telecommunications). It was possible to identify different excitonic complex transitions using the same methods mentioned above. However, this sample shows a lower optical quality. The broader µ-PL linewidth could be explained by the high indium content in the metamorphic layer. This extra Indium content might cause a higher density of structural defects, resulting in a spectral diffusion effect on the µ-PL linewidth [5]. In conclusion, we report on the growth of low density metamorphic QD structures grown on GaAs (at two indium compositions) and single QD optical characterization, with emission up to 1300nm. These results show that metamorphic QDs could be valuable candidates for the development of single photon sources emitting at the second telecommunication window wavelength.
1.3 µm single quantum dot emission from metamorphic InAs/InGaAs nanostructures
Seravalli Luca;Trevisi Giovanna;Frigeri Paola;
2011
Abstract
Self assembled InAs/GaAs Quantum Dots (QD) have received much interest both from the standpoint of fundamental physics and technological applications. In consequence, thanks to these nanostructures important advances in optoelectronics and quantum technologies have been achieved [1]. However, these QDs have also some disadvantages, concerning to a strong decrease of the emission intensity with the temperature or difficulties to obtain emission wavelengths beyond 1 ?m, when they are grown on GaAs substrates [2]. In this work we show an original approach to grow by Molecular Beam Epitaxy (MBE) long wavelength emitting metamorphic InAs/InGaAs/ GaAs QDs, with high single nanostructure optical quality [3]. Subcritical InAs coverages allow to obtain low QD density (108 cm-2) and the reduction of QD strain and confining potential provided by the metamorphic InxGa1-xAs confining layer results in emission wavelengths at 1.3 ?m. For this purpose, two samples with different Indium compositions have been studied (x=0.15, 0.30). At low excitation power the micro-Photoluminescence (?PL) spectra show emission lines characteristic of a single QD. Figure 1a shows ?PL spectra from a single QD emitting at around 1171 nm in a sample with x = 0.15. The spectra show typical excitonic (Xn) and biexcitonic (XXn) lines, which can be identified studying the integrated intensity power dependence and the selective optical pumping effect associated to local unintentional impurities [4]. In sample with x = 0.30 (Figure 1b) it was observed excitonic emission around 1.336 µm (second window of telecommunications). It was possible to identify different excitonic complex transitions using the same methods mentioned above. However, this sample shows a lower optical quality. The broader µ-PL linewidth could be explained by the high indium content in the metamorphic layer. This extra Indium content might cause a higher density of structural defects, resulting in a spectral diffusion effect on the µ-PL linewidth [5]. In conclusion, we report on the growth of low density metamorphic QD structures grown on GaAs (at two indium compositions) and single QD optical characterization, with emission up to 1300nm. These results show that metamorphic QDs could be valuable candidates for the development of single photon sources emitting at the second telecommunication window wavelength.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
