Improved optical properties of InAs submonolayer quantum dots in GaAsSb/InGaAs double-well structure (original) (raw)
Related papers
Photoluminescence study and parameter evaluation in InAs quantum dot-in-a-well structures
Materials Science and Engineering: B, 2011
The photoluminescence (PL), its temperature and power dependences have been studied in InAs quantum dots (QDs) embedded in the symmetric In0.15Ga0.85As/GaAs quantum well (QW) with QDs grown at different temperatures (470-535 •C). The ground state (GS) PL peaks shift with increasing QD growthtemperatures: the red shift is observed when temperature increased from 480 to 510 •C and the blue shift is typical when the temperature raised from 510 to 535 •C. The fitting procedure (on the base of Varshni relation) has been applied to the analysis of GS PL peak positions versus temperatures. Obtained fitting parameters are compared with corresponding data for the temperature variation of energy band gap in the bulk InAs crystal and in the In0.21Ga0.79As alloy. The comparison has revealed that the structures with QDs grown at 490-510 •C have the same fitting parameters as the bulk InAs crystal. However in structures with QDs grown at the temperatures 470, 525 and 535 •C the fitting parameters testify that Ga/In inter-diffusion between QDs and a QWhas been realized. It is shown that the Ga/In inter-diffusion process is accompanied by the appearance of nonradiative recombination defects.
Influence of GaAsBi Matrix on Optical and Structural Properties of InAs Quantum Dots
Nanoscale research letters, 2016
InAs/GaAsBi dot-in-well structures were fabricated using gas-source molecular beam epitaxy and investigated for its optical and structural properties. GaAsBi-strained buffer layer and strain reduction layer are both effective to extend the photoluminescence (PL) emission wavelength of InAs quantum dot (QD). In addition, a remarkable PL intensity enhancement is also obtained compared with low-temperature-grown GaAs-capped InAs QD sample. The GaAsBi matrix also preserves the shape of InAs QDs and leads to increase the activation energy for nonradiative recombination process at low temperature. Lower density and larger size of InAs QDs are obtained on the GaAsBi surface compared with the QDs grown on GaAs surface.
Effects of GaAs(Sb) cladding layers on InAs/AlAsSb quantum dots
Applied Physics Letters, 2013
The structural and optical properties of InAs self-assembled quantum dots buried in AlAs 0.56 Sb 0.44 barriers can be controlled using GaAs 1Àx Sb x cladding layers. These cladding layers allow us to manage the amount of Sb immediately underneath and above the InAs quantum dots. The optimal cladding scheme has a GaAs layer beneath the InAs, and a GaAs 0.95 Sb 0.05 layer above. This scheme results in improved dot morphology and significantly increased photoluminescence (PL) intensity. Both power-dependent and time-resolved photoluminescence confirm that the quantum dots have type-II band alignment. Enhanced carrier lifetimes in this quantum dot system show great potential for application in intermediate band solar cells. V
Carrier dynamics in InAs quantum dots embedded in InGaAs/GaAs multi quantum well structures
Journal of Physics: Conference Series, 2007
Ground and multi excited state photoluminescence, as well as its temperature dependence, in InAs quantum dots embedded in symmetric In x Ga 1-x As/GaAs (x=0.15) quantum wells (DWELL) have been investigated. The solution of the set of rate equations for exciton dynamics (relaxation into QWs or QDs and thermal escape) solved by us earlier is used for analysis the variety of thermal activation energies of photoluminescence thermal quenching for ground and multi excited states of InAs QDs. The obtained solutions were used at the discussion of the variety of activation energies of PL thermal quenching in InAs QDs. It is revealed three different regimes of thermally activated quenching of the QD PL intensity. These three regimes were attributed to thermal escape of excitons: i) from the high energy excited states of InAs QDs into the WL with follows exciton re-localization; ii) from the In x Ga 1-x As QWs into the GaAs barrier and iii) from the WL into the GaAs barrier with their subsequent nonradiative recombination in GaAs barrier.
Photoluminescence characteristics of InAs self-assembled quantum dots in InGaAs∕GaAs quantum well
Journal of Applied Physics, 2007
Three different InAs quantum dots ͑QDs͒ in an InGaAs/ GaAs quantum well were formed and investigated by time-resolved and temperature dependent photoluminescence ͑PL͒. A strong PL signal emitting at ϳ1.3 m can be obtained at room temperature with a full width at half maximum of only 28 meV. Dots-in-a-well structures result in strong stress release and large size InAs QDs which lead to narrowing and redshifting of PL emissions, enhancement of carrier migration, increasing carrier density in QDs, achievement of good PL lifetime stability on temperature, and improving the QD quality.
InAs/GaAsSb quantum dot solar cells
The hybrid structure of GaAs/GaAsSb quantum well (QW)/InAs quantum dots solar cells (QDSCs) is analyzed using power-dependent and temperature-dependent photoluminescence. We demonstrate that placing the GaAsSb QW beneath the QDs forms type-II characteristics that initiate at 12% Sb composition. Current density-voltage measurements demonstrate a decrease in power efficiency with increasing Sb composition. This could be attributed to increased valence band potential in the GaAsSb QW that subsequently limits hole transportation in the QD region. To reduce the confinement energy barrier, a 2 nm GaAs wall is inserted between GaAsSb QW and InAs QDs, leading to a 23% improvement in power efficiency for QDSCs.
Journal of Materials Science: Materials in Electronics, 2017
[6] and tunneling diodes [7]. It was shown that the disadvantages of InAs/GaAs or InAs/InGaAs QD systems are connected with QD non-homogeneous surface distribution, significant dispersion of QD sizes or QD compositions that lead to the differences in optical device parameters [8-10]. Additional factor that has an impact on QD device parameters is the In/Ga atom inter-diffusion between the QDs and QWs. In/Ga intermixing can be realized on the different stages of QD and QW growth processes. A number of papers were published recently concerning the study of In/Ga intermixing at thermal annealing [11-13]. The main attention in these papers was connected with the spectral shift investigation for QD emission that was detected after thermal annealing. However the essentially more information concerning In/Ga intermixing between QDs and QW can be obtained at the joint investigation of QD emission and QW parameters using high-resolution X ray diffraction (HR-XRD) method [14, 15]. In present paper the emission and HR-XRD were studied in InGaAs/GaAs QW structures with embedded InAs QDs grown at different temperatures from the range 470-535 °C. 2 Experimental conditions InAs QD structures were grown by the molecular beam epitaxy (MBE) on the (001) semi-insulating GaAs substrates. Each structure includes a 200 nm GaAs buffer layer and a 100 nm GaAs upper final capping layer that were grown at 600 °C (Fig. 1). Between GaAs layers there are a second In 0.15 Ga 0.85 As buffer layer (2 nm), then the self-organized InAs QD array formed by the deposition of 2.4 ML of InAs, and first capping In 0.15 Ga 0.85 As layers (Fig. 1). Both the buffer and capping In 0.15 Ga 0.85 As layers were grown at 510 °C. The growth temperature of InAs QDs varies for Abstract GaAs/In 0.15 Ga 0.85 As/GaAs QWs with embedded InAs QDs grown at different temperatures have been studied by means of the photoluminescence (PL), X ray diffraction (XRD) and high resolution XRD (HR-XRD) methods. PL study has detected varying of QD parameters and HR-XRD permits monitoring the QW parameters. It is shown that increasing the QD growth temperature up to 510 °C leads to raising the QD sizes, to shift of QD emission peak to low energy and increasing the PL intensity of QDs. Simultaneously Ga/In atom intermixing is realized mainly between the InGaAs buffer and InAs wetting layers and did not influent on the InAs QD composition. At higher QD growth temperatures (525-535 °C) the PL intensity of QDs decreases significantly together with decreasing the QD heights and the shift of PL peaks into higher energy. Fitting the HR-XRD results has revealed that Ga/In atom intermixing involves the composition changes in buffer and wetting layers, as well as in QDs. The mentioned optical and structural effects have been discussed in details.
Room temperature emission at 1.6 μm from InGaAs quantum dots capped with GaAsSb
Applied Physics Letters, 2005
Room temperature photoluminescence at 1.6 m is demonstrated from InGaAs quantum dots capped with an 8 nm GaAsSb quantum well. Results obtained from various sample structures are compared, including samples capped with GaAs. The observed redshift in GaAsSb capped samples is attributed to a type II band alignment and to a beneficial modification of growth kinetics during capping due to the presence of Sb. The sample structure is discussed on the basis of transmission electron microscopy results.
Journal of Luminescence, 2020
In this study, the optical properties of InAs quantum dots (QDs) were characterized using photoluminescence (PL) measurements. The QDs, capped with GaAs and GaAs 1À x Sb x (x ¼ 6%) strain-reducing layer (SRL), were grown by Molecular Beam Epitaxy. Temperature-dependent photoluminescence (TDPL) of both ground state (GS) and first excited state (ES) was carried out through the analysis of the PL peak position as well as the integrated PL intensity. The temperature dependence of the integrated PL intensity shows the carrier trapping in the potential barrier at the interface between the capping layer and QDs in both samples at low temperatures for the GS and ES. The Excitation density dependent photoluminescence (EDPL) showed a redshift of the GS and ES PL peak energies with increasing excitation density. We attribute this variation to the bandgap renormalization (BGR) effect. The potential barrier reduction for the GaAsSb-capped QDs increases carrier injection efficiency inside the QDs, giving rise to a larger BGR effect compared to the QDs capped with GaAs. With increasing temperature, BGR redshift varies considerably for the GaAs-capped QDs but less for the Q with GaAsSb SRL. This effect was explained using the population rate of carriers inside the QDs while taking into account the nonradiative recombination process for the two samples. Furthermore, the variation of the integrated intensity with the excitation power density grows superlinearly for the two samples for a temperature range from 10 K to 220 K. This behavior was explained by the random capture of carriers in the dots. The sample with GaAsSb SRL having a smaller potential barrier has reduced superlinear dependence at low temperatures. Losses mechanism has a significant impact on increasing the superlinear dependence at high temperatures. The ES showed a stronger superlinearity compared to the GS. This study helps to understand the optical mechanisms in some devices, such as QD lasers.