Investigation of the optical properties of InAs/InGaAs/GaAs quantum dot in quantum well multilayer structures for infrared photodetectors (original) (raw)
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Inter-band optical transitions in InAs submonolayer and Stranski-Krastanov quantum dot (QD) in quantum well (QW) nanostructures are studied by means of room temperature surface photovoltage (SPV) spectroscopy taking advantage of its high sensitivity and contactless nature. The QD optical transitions are identified by the combined analysis of SPV amplitude and phase spectra and are in agreement with photoluminescence results. The SPV spectra have further revealed the optical transitions in all other relevant layers in the structures-wetting layer, QWs, and AlGaAs barriers. The analysis of the SPV phase spectra has revealed that the carrier separation and transport in the QD structure is determined by the energy band bending, resulting from the slight residual p-type doping. The complicated interaction between the SPV signals from the nanostructure and the semi-insulating GaAs substrate is discussed and clarified. The advantages of the SPV spectroscopy for characterizing complicated nanostructures at room temperature are highlighted.
Surface photovoltage spectroscopy of interdiffused InAs/InGaAlAs quantum dashes-in-well structure
We report room temperature surface photovoltage (SPV) spectroscopy studies of both as-grown and interdiffused InAs quantum dash (QD)–in–InAlGaAs quantum well (QW) structures grown by molecular beam epitaxy on (100) InP substrates. The interdiffusion is achieved by means of rapid thermal annealing at 800 ºC for 30 s. The SPV spectra reveal step-like structures related to the optical absorption in the QDs, QWs, InGaAlAs separate carrier confinement layer, InAlAs lower cladding layer and InP substrate. The annealing results in a high-energy shift of these spectral structures. The shift is attributed to the group-III atoms intermixing from the thermal induced interdiffusion across the heterointerfaces. The effect of interdiffusion is larger for the elements with larger surface-to-volume ratio (QDs and QWs). The blue shift of the QD transition is observed also in the photoluminescence spectra. The results contribute to the optimization of the technological procedure for QD bandgap tuning via the interdiffusion technique.
We report the study of interband optical transitions in the interdiffused InAs quantum dash QD in InAlGaAs quantum well QW structures using room temperature surface photovoltage SPV spectroscopy. SPV signals have been detected from all relevant portions of both the as-grown and interdiffused structures including the QD, QW, and cladding layer. The effect of group-III intermixing on the interband optical transition energies in the interdiffused structures has also been revealed by the SPV spectroscopy, and the results have been confirmed by photoluminescence measurements. The SPV investigation shows that the compositional intermixing occurs not only between the dash and the surrounding well but also between the well and the surrounding barrier. The results demonstrate the potential of the SPV spectroscopy as a nondestructive, contactless method to characterize optical transitions in complex semiconductor nanostructures at room temperature.
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.
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.
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.
Investigation of the electrical and optical properties of InAs/InGaAs dot in a well solar cell
The electroreflectance (ER) and currentevoltage (JeV) of InAs/InGaAs dots in a well (DWELL) solar cell (SC) were measured to examine the optical and electrical properties. To investigate the carrier capturing and escaping effects in the quantum dot (QD) states the above and below optical biases of the GaAs band gap were used. In the reverse bias region of the JeV curve, the tunneling effect in the QD states was observed at low temperature. The ideality factors (n) were calculated from the JeV curves taken from various optical bias intensities (I ex). The changes in the ideality factor (n) and short circuit current (J SC) were attributed mainly to carrier capture at low temperature, whereas the carrier escaping effect was dominant at room temperature. ER measurements revealed a decrease in the junction electric field (F J) due to the photovoltaic effect, which was independent of the optical bias source at the same temperature. At low temperature, the reduction of photovoltaic effect could be explained by the enhancement carrier capturing effect due to the strong carrier confinement in QDs.
Intersublevel transitions in InAs/GaAs quantum dots infrared photodetectors
Applied Physics Letters, 1998
Thermal generation rate in quantum dots ͑QD͒ can be significantly smaller than in quantum wells, rendering a much improved signal to noise ratio. QDs infrared photodetectors were implemented, composed of ten layers of self-assembled InAs dots grown on GaAs substrate. Low temperature spectral response shows two peaks at low bias, and three at a high one, polarized differently. The electronic level structure is determined, based on polarization, bias, and temperature dependence of the transitions. Although absorbance was not observed, a photoconductive signal was recorded. This may be attributed to a large photoconductive gain due to a relatively long lifetime, which indicates, in turn, a reduced generation rate.
Journal of Lightwave Technology, 2018
In this work, we have demonstrated the first InAs/InGaAs/GaAs quantum dots-in-a-well (DWELL) photodetector monolithically grown on silicon substrate. We studied both the optical and electrical characteristics of the DWELL photodetectors. Time-resolved photoluminescence spectra measured from the DWELL photodetector revealed a long carrier lifetime of 1.52 ns. A low dark current density of 2.03×10-3 mA/cm 2 was achieved under 1 V bias at 77 K. The device showed a peak responsivity of 10.9 mA/W under 2 V bias at the wavelength of corresponding detectivity was 5.78×10 8 cm•Hz 1/2 /W. These results demonstrated that these silicon based DWELL photodetectors are very promising for future mid-infrared applications, which can enjoy the potential benefit from mid-infrared silicon photonics technology. Index Termsinfrared photodetector, quantum dots-in-a-well, silicon substrate. I. INTRODUCTION id-wave infrared (MWIR) photodetectors have many applications in areas such as gas monitoring, chemical sensing, and infrared imaging [1-3]. Traditional bulk photodetectors like mercury-cadmium-telluride (MCT), while they have been demonstrated with high responsivity and specific detectivity, they still suffer from material non-uniformity, problems related to epitaxial growth of mercury-based compounds, and the relatively high cost of the CdZnTe substrate [4, 5]. Quantum wells infrared photodetectors (QWIPs), which utilize