Abstract:Suppression of the photoluminescence quenching effect in self-assembled In As ∕ Ga As quantum dots Appl. Phys. Lett. 87, 053109 (2005) The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80 K after excitation of electron-hole pairs due to interband tr… Show more
“…3). As well the onset of both the absorption spectra at 0.68 eV, we attribute to the transition from EL2 defect center to the conduction band considering the possible way through the shallow defect levels [24–27, 29]. Similar redshift of EL2-related bands in optical transition have been described for InGaAs/GaAs nanostructures [27, 30].…”
Optical and photoelectric properties of metamorphic InAs/InGaAs and conventional pseudomorphic InAs/GaAs quantum dot (QD) structures were studied. We used two different electrical contact configurations that allowed us to have the current flow (i) only through QDs and embedding layers and (ii) through all the structure, including the GaAs substrate (wafer). Different optical transitions between states of QDs, wetting layers, GaAs or InGaAs buffers, and defect-related centers were studied by means of photovoltage (PV), photoconductivity (PC), photoluminescence (PL), and absorption spectroscopies. It was shown that the use of the InGaAs buffer spectrally shifted the maximum of the QD PL band to 1.3 μm (telecommunication range) without a decrease in the yield. Photosensitivity for the metamorphic QDs was found to be higher than that in GaAs buffer while the photoresponses for both metamorphic and pseudomorphic buffer layers were similar. The mechanisms of PV and PC were discussed for both structures. The dissimilarities in properties of the studied structures are explained in terms of the different design. A critical influence of the defects on the photoelectrical properties of both structures was observed in the spectral range from 0.68 to 1.0 eV for contact configuration (ii), i.e., in the case of electrically active GaAs wafer. No effect of such defects on the photoelectric spectra was found for configuration (i), when the structures were contacted to the top and bottom buffers; only a 0.83 eV feature was observed in the photocurrent spectrum of pseudomorphic structure and interpreted to be related to defects close to InAs/GaAs QDs.
“…3). As well the onset of both the absorption spectra at 0.68 eV, we attribute to the transition from EL2 defect center to the conduction band considering the possible way through the shallow defect levels [24–27, 29]. Similar redshift of EL2-related bands in optical transition have been described for InGaAs/GaAs nanostructures [27, 30].…”
Optical and photoelectric properties of metamorphic InAs/InGaAs and conventional pseudomorphic InAs/GaAs quantum dot (QD) structures were studied. We used two different electrical contact configurations that allowed us to have the current flow (i) only through QDs and embedding layers and (ii) through all the structure, including the GaAs substrate (wafer). Different optical transitions between states of QDs, wetting layers, GaAs or InGaAs buffers, and defect-related centers were studied by means of photovoltage (PV), photoconductivity (PC), photoluminescence (PL), and absorption spectroscopies. It was shown that the use of the InGaAs buffer spectrally shifted the maximum of the QD PL band to 1.3 μm (telecommunication range) without a decrease in the yield. Photosensitivity for the metamorphic QDs was found to be higher than that in GaAs buffer while the photoresponses for both metamorphic and pseudomorphic buffer layers were similar. The mechanisms of PV and PC were discussed for both structures. The dissimilarities in properties of the studied structures are explained in terms of the different design. A critical influence of the defects on the photoelectrical properties of both structures was observed in the spectral range from 0.68 to 1.0 eV for contact configuration (ii), i.e., in the case of electrically active GaAs wafer. No effect of such defects on the photoelectric spectra was found for configuration (i), when the structures were contacted to the top and bottom buffers; only a 0.83 eV feature was observed in the photocurrent spectrum of pseudomorphic structure and interpreted to be related to defects close to InAs/GaAs QDs.
“…Considering the data about intrinsic and crystal defects in In(Ga)As/GaAs heterostructures obtained from deep level transient spectroscopy, 23,24 PC spectroscopy, and thermally stimulated current, 16,17,25 we attribute the onset of the absorption spectrum at 0.68 eV to a transition from a EL2 defect center in the InGaAs/GaAs layer where defect concentration is high. 26,27 It is known that in semi-insulating GaAs, the level of EL2 center is located near 0.75 eV below the conduction band, 28 but in strained InGaAs the energy of transition involving EL2 defect states is reduced.…”
Section: Discussionmentioning
confidence: 99%
“…26,27 It is known that in semi-insulating GaAs, the level of EL2 center is located near 0.75 eV below the conduction band, 28 but in strained InGaAs the energy of transition involving EL2 defect states is reduced. 25,[28][29][30] The fact that no signal below 0.9 eV is observed in the photocurrent spectra indicates that the presence of defects related to the plastic relaxation of the InGaAs MB 18 does not prevent the detection of photocarriers coming from QDs. It should be reminded here that the contact configuration used in these measurements allowed us to exclude the InGaAs/GaAs interface region that is known to have a higher defect density.…”
Section: Discussionmentioning
confidence: 99%
“…As for the InGaAs defects, they are usually not photoactive but affect the photoelectrical properties of such heterostructures by trapping the nonequilibrium charge carriers 15,16,25 and, hence, reducing the radiative recombination efficiency: for this reason, additional experiments are necessary to study InGaAs defects.…”
Articles you may be interested inCalculation of metamorphic two-dimensional quantum energy system: Application to wetting layer states in InAs/InGaAs metamorphic quantum dot nanostructures Single quantum dot emission at telecom wavelengths from metamorphic InAs/InGaAs nanostructures grown on GaAs substrates Appl. Phys. Lett. 98, 173112 (2011); 10.1063/1.3584132
Properties of wetting layer states in low density InAs quantum dot nanostructures emitting at 1.3 μ m : Effects of InGaAs cappingWe present the study of optical and photoelectric properties of InAs quantum dots (QDs) grown on a metamorphic In 0.15 Ga 0.85 As buffer layer: such nanostructures show efficient light emission in the telecom window at 1.3 lm (0.95 eV) at room temperature. We prepared a sample with vertical geometry of contacts isolated from the GaAs substrate. The structure is found to be photosensitive in the spectral range above 0.9 eV at room temperature, showing distinctive features in the photovoltage and photocurrent spectra attributed to QDs, InAs wetting layer, and In 0.15 Ga 0.85 As metamorphic buffer, while a drop in the photoelectric signal above 1.36 eV is related to the GaAs layer. No effect of defect centers on the photoelectrical properties is found, although they are observed in the absorption spectrum. We conclude that metamorphic QDs have a low amount of interface-related defects close to the optically active region and charge carriers can be effectively collected into InAs QDs. V C 2015 AIP Publishing LLC. [http://dx.
“…The perfect crystal planes for the GaAs spacer layers were observed. As was shown earlier [13] by geometrical phase analysis of HRTEM images, the non-uniform elastic stress relaxation mainly occurs at the tip of the dot and that the underlying GaAs layer is under tension.Fig. 2(Color online) Cross-sectional TEM images of InGaAs/GaAs QWR ( a ) and quantum dot-chain ( b ) structure along the [110] direction
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An experimental study of the photoconductivity time decay in InGaAs/GaAs quantum dot chain structures is reported. Different photoconductivity relaxations resulting from spectrally selecting photoexcitation of InGaAs QWR or QDs as well as GaAs spacers were measured. The photoconductivity relaxation after excitation of 650 nm follows a stretched exponent with decay constant dependent on morphology of InGaAs epitaxial layers. Kinetics with 980 nm excitation are successfully described by equation that takes into account the linear recombination involving Shockley–Read centers in the GaAs spacers and bimolecular recombination via quantum-size states of InGaAs QWRs or QDs.
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