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The morphology and optical properties of In(0.35)Ga(0.65)As/GaAs quantum dots (QDs) grown on (210), (311)A, (711)A, (731) and (100) substrates are investigated. QDs formed on (210) and (731) oriented substrates are grown by molecular beam epitaxy. Regular QDs are observed on (100), (311)A, and (711)A. Randomly distributed QDs and comet-shaped QDs form on (210) and (731) substrates, respectively. A high density of QDs on the order of 10(11) cm(-2) are obtained from (711)A. The optical measurement shows a spectrum linewidth (FWHM = 74.3 nm) of QDs on GaAs (210) three times wider than GaAs (100) substrate. Long exciton decay times, over 1 ns, are also measured by time-resolved photoluminescence technique for all samples. Our results demonstrate the potential for QDs on GaAs high index substrates for wideband applications.

Normal incident photodetection at mid infrared spectral region is achieved using the intersublevel transitions from strain-free GaAs quantum dot pairs in Al(0.3)Ga(0.7)As matrix. The GaAs quantum dot pairs are fabricated by high temperature droplet epitaxy, through which zero strain quantum dot pairs are obtained from lattice matched materials. Photoluminescence, photoluminescence excitation optical spectroscopy, and visible-near-infrared photoconductivity measurement are carried out to study the electronic structure of the photodetector. Due to the intersublevel transitions from GaAs quantum dot pairs, a broadband photoresponse spectrum is observed from 3 to 8 microm with a full width at half-maximum of approximately 2.0 microm.

Ultralow density (approximately 10(6)/cm(2)) of twin InAs quantum dot (QD) hybrid structure was grown by a droplet epitaxy technique. The photoluminescence (PL) from ensemble and individual twin InAs QD structures showed a bimodal behavior and an energy transfer between the well-separated (approximately 190 nm) twin QDs, which was supposedly due to the special wetting ring that built the channel for exciton transfer. This research demonstrates a novel approach to fabricate lateral InAs QD pairs as the candidate for a laterally coupled QD molecule.

InAs quantum dots (QDs) have been grown on a GaAs (001) substrate in the subcritical region of InAs coverage for transition from a 2-dimensional (2D) to a 3-dimensional growth mode. Evolution of QDs and the corresponding wetting layer (WL) with InAs coverage has been investigated. Under specific growth conditions, quantum dot formation was observed only in samples where InAs coverage is more than 1.48 ML. The QD density increases sharply with InAs deposition initially but slows down with increased coverage. Photoluminescence (PL) shows the existence of a third peak, other than QD and WL peaks, at the low energy side of the WL peak, which is named the precursor peak. Evidence is presented supporting the theory that this peak is due to 2D InAs islands on a monolayer of InAs, which are small enough to localize excitons. Meanwhile, the WL peak is due to larger InAs islands under high compressive strain. During QD formation, the WL peak energy increases with the increase in InAs deposition. This is due to the sudden transfer of material from the bigger size of InAs islands to the QD. Our results show that the QD, WL, and precursor peaks coexist near the onset of QD formation. The power dependence of the three PL peaks is evident, which supports to our conclusion. [ABSTRACT FROM AUTHOR]

Stacking growth of the InGaAs quantum dots (QDs) on top of a carrier injection layer is a very useful strategy to develop QD devices. This research aims to study the carrier injection effect in hybrid structures with a layer of In0.4Ga0.6As surface quantum dots (SQDs), coupled to an injection layer of either one layer of In0.4Ga0.6As buried QDs (BQDs) or an In0.15Ga0.85As quantum well (QW), both through a 10 nm GaAs thin spacer. Spectroscopic measurements show that carrier capture and emission efficiency for SQDs in the BQD injection structure is better than that of the QW injection, due to strong physical and electrical coupling between the two QD layers. In the case of QW injection, although most carriers can be collected into the QW, they then tunnel into the wetting layer of the SQDs and are subsequently lost to surface states via non-radiative recombination. Therefore, the QW as an injection source for SQDs may not work as well as the BQDs for stacking coupled SQDs structures. [ABSTRACT FROM AUTHOR]

GaSb quantum dots (QDs) have been grown by droplet epitaxy within InAlAs barrier layers on an InP (001) substrate. The droplet growth mode facilitates a larger size (average height ∼4.5 nm) and a lower density (∼6.3 × 109 cm-2) for the QDs than would be expected for the 4% lattice mismatch between GaSb and InAlAs. A type-II band alignment between the GaSb QDs and the InAlAs barriers is revealed by photoluminescence (PL) through a prominent blue-shift of ∼0.11 eV resulting from a six orders of magnitude increase in excitation power. Further confirmation of the type-II nature of these QDs is found through time-resolved PL studies showing a biexponential decay with a long carrier lifetime of ∼10.9 ns. These observations reveal new information for understanding the formation and properties of GaSb/InAlAs/InP QDs, which may be an optimum system for the development of both efficient memory cells and photovoltaic devices. [ABSTRACT FROM AUTHOR]

Self-assembled quantum dots grown by molecular beam epitaxy have been a hotbed for various fundamental research and device applications over the past decades. Among them, InAs/GaAs quantum dots have shown great potential for applications in quantum information, quantum computing, infrared photodetection, etc. Though intensively studied, some of the optical nonlinear properties of InAs/GaAs quantum dots, specifically the associated two-photon absorption of the wetting and barrier layers, have not been investigated yet. Here we report a study of the photoluminescence of these dots by using direct two-photon excitation. The quadratic power law dependence of the photoluminescence intensity, together with the ground-state resonant peak of quantum dots appearing in the photoluminescence excitation spectrum, unambiguously confirms the occurrence of the direct two-photon absorption in the dots. A three-level rate equation model is proposed to describe the photogenerated carrier dynamics in the quantum dot-wetting layer-GaAs system. Moreover, higher-order power law dependence of photoluminescence intensity is observed on both the GaAs substrate and the wetting layer by two-photon excitation, which is accounted for by a model involving the third-harmonic generation at the sample interface. Our results open a door for understanding the optical nonlinear effects associated with this fundamentally and technologically important platform. [ABSTRACT FROM AUTHOR]

In this paper, 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 ${\text{2.03}}\times {\text{10}}^{-3}\;{\text{mA/cm}}^{2}$ 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 6.4 μm at 77 K, and the corresponding detectivity was ${\text{5.78}}\times {\text{10}}^{8}\,{{\text{cm}\cdot \text{Hz}}}^{1/2}{\text{/W}}$. 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. [ABSTRACT FROM AUTHOR]

Isolated single quantum dots (QDs) enable the investigation of quantum-optics phenomena for the application of quantum information technologies. In this work, ultralow-density InAs QDs are grown by combining droplet etching epitaxy and the conventional epitaxy growth mode. An extreme low density of QDs (∼106 cm−2) is realized by creating low-density self-assembled nanoholes with the high temperature droplet etching epitaxy technique and then nanohole-filling. The preferred nucleation of QDs in nanoholes has been explained by a theoretical model. Atomic force microscopy and the photoluminescence technique are used to investigate the morphological and optical properties of the QD samples. By varying In coverages, the size of InAs QDs can be controlled. Moreover, with a thin GaAs cap layer, the position of QDs remains visible on the sample surface. Such a low density and surface signature of QDs make this growth method promising for single QD investigation and single dot device fabrication. [ABSTRACT FROM PUBLISHER]

Photoluminescence properties of InAs/GaAs1-xSbx quantum dots (QDs) are investigated with respect to the Sb-composition of x=0, 0.15, and 0.25. The QDs demonstrate a type-II band alignment for x=0.15 and 0.25. In contrast, with well-defined InAs/GaAs QDs, the InAs/GaAs1-xSbx QDs exhibit overlapping spectral features with increasing laser excitation intensity, which are determined to be the result of different carrier recombination routes, including both type-I and type-II pathways. Our investigation indicates that the optical behavior and the carrier dynamics in these InAs/GaAs1-xSbx QDs are much more complicated than in the InAs/GaAs QD counterparts. It provides very useful information for understanding the band structure and carrier dynamics of type-II InAs/GaAs1-xSbx QDs. [ABSTRACT FROM AUTHOR]

Optical response of the indium arsenide (InAs)/gallium arsenide (GaAs) quantum dots (QDs) with a bimodal distribution is investigated through varying an initial GaAs capping layer between 35 and 18 monolayers. Photoluminescence (PL) measurements confirm that a thinner initial capping layer can reduce the QD dimensions and also modify the population ratio between the large QDs and the small QDs. Therefore, PL quenching related to QD dimension and carrier transfer between the bimodal QD populations has been affected. Manipulation of the initial GaAs capping layer provides a feasible approach to tailor the formation and optical performance of InAs QDs for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Carrier transfer in vertically-coupled InAs/GaAs quantum dot (QD) pairs is investigated. Photoluminescence (PL) and PL excitation spectra measured at low temperature indicate that the PL peak intensity ratio between the emission from the two sets of QDs--i.e., the relative population of carriers between the two layers of QDs--changes with increasing excitation intensity. Temperature-dependent PL reveals unexpected non-monotonic variations in the peak wavelength and linewidth of the seed layer of QDs with temperature. The PL intensity ratio exhibits a "W" behavior with respect to the temperature due to the interplay between temperature and excitation intensity on the inter-layer carrier transfer. [ABSTRACT FROM AUTHOR]

The continuum state associated with type-II In0.46Al0.54As/Al0.54Ga0.46As quantum dots (QDs) is investigated. Emission from the continuum states of the QDs is directly observed in photoluminescence (PL) spectra. The PL excitation and time-resolved PL spectra reveal an efficient carrier relaxation from the AlGaAs barrier into the InAlAs QD ground state via the continuum states. The temperature dependence of the PL spectra shows a decreasing PL linewidth and a strong redshift of the peak energy at low temperature, indicating that carriers are redistributed through the continuum states by thermal activation and lateral transfer. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]

Optical properties of In0.46Al0.54As/ Ga0.46Al0.54As quantum dots (QDs) have been investigated by photoluminescence (PL). At a low temperature of 8K, the PL peak energy blue-shifts 44 meV and the linewidth broadens by 21 meV as the excitation intensity increases by four orders of magnitude. As the temperature increases, the QD spectra demonstrate a fast redshift and narrowing from 35 K. These observations have been explained by the type-II nature of QDs and the lateral carrier transfer due to electronic coupling between neighboring QDs. A special double exponential decay behavior indicates the coexistence of type-I and type-II band alignment in this QD sample. [ABSTRACT FROM AUTHOR]

The optical analysis of multilayer structures formed from the topmost layer of InGaAs/GaAs quantum rings (QRs) grown on a vertically stacked and laterally aligned InGaAs/GaAs quantum dot (QD) superlattice has been performed to elucidate the nature of the contribution from each layer. These hybrid structures representing a coupled QR chain layer and the layers of self-assembled QD chains display strong optical anisotropy. Unusually strong oscillations are observed in the circularly polarized photoluminescence (PL) intensities under magnetic field for emissions in the spectral range of the QD structure and these oscillations occur simultaneously with weaker oscillations related to the Aharonov-Bohm interference that modulates the emissions from the QR top layer of the structure. The behavior seen in the magneto-PL spectrum is interpreted in terms of joint effects associated to strain, spatial, and magnetic field confinements on the valence band states forming the magnetoexciton ground state of this multilayered structure. The result can be ascribed to a magnetically induced dark exciton contribution where the heavy-hole (type II) state becomes localized outside, whereas light-hole (type I) as well as electron states remain inside the spatial confinement area of the QD. [ABSTRACT FROM AUTHOR]

Abstract: The realization of high efficiency quantum dot intermediate band solar cells is challenging due to the thermally activated charge escaping at high temperatures. The enhancement in short circuit current of quantum dot solar cells is largely undermined by the voltage loss. In this paper, InAs/GaAs quantum dot solar cells with direct Si doping in the quantum dots are studied. The open circuit voltage is improved with increasing doping concentration in the quantum dots. The recovery of open circuit voltage as large as 105mV is measured. This voltage recovery is attributed to suppressed charge thermal escaping from quantum dots. The suppressed thermal coupling is supported by the external quantum efficiency and photoluminescence measurements. [Copyright &y& Elsevier]

We present the fabrication of ordered quantum rings by the conversion of partially capped quantum dots. Morphological transformation of quantum dots to quantum rings is demonstrated by partially capping self-assembled quantum dots. Quantum rings have been fabricated on high index surfaces by this growth technique. The lateral ordering of quantum rings is introduced by engineering the strain field of a multi-layer InGaAs superlattice template. By using high index surfaces, the one-dimensional ordering of quantum rings on GaAs (100) surface was observed to evolve into two-dimensional aligned quantum ring arrays. [ABSTRACT FROM AUTHOR]

We demonstrate low-density quantum dot molecules (QDMs) by selective etching using In droplets as a mask. Selective etching is performed with InGaAs QDMs buried underneath GaAs capping layer, on which In droplets are formed by droplet epitaxy using molecular beam epitaxy. During the chemical etching, the droplets act as a mask and QDMs underneath the droplets that only survive. Photoluminescence measurement from the selectively etched QDMs in mesa structures shows a much reduced intensity, which indicates low-density QDMs. This technique provides a simple and flexible method to attain low-density QDMs. The density can be easily modified by the control of the size and density of In droplets, which is suitable for single QDM spectroscopy and for their device applications. [ABSTRACT FROM PUBLISHER]

Droplet epitaxy is a flexible nanomaterial growth technique and is a potential method to fabricate advanced electronic and optoelectronic devices. Here, we report strain-free GaAs/Al0.33Ga0.67As quantum ring solar cells fabricated by droplet epitaxy technique. Photoluminescence is used to study the electronic structure of the lattice-matched GaAs/Al0.33Ga0.67As quantum ring solar cells. Post-growth thermal annealing is used to improve the optical quality of the solar cell as well as device efficiency. A power conversion efficiency of 1.8% is demonstrated from a prototype quantum ring solar cell. This work opens new opportunities for quantum dot solar cells with strain-free nanostructures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carrier injection hybrid structure from quantum well to surface quantum dots (SQDs) • All hybrid structures obtain an enhancement for PL intensity due to carrier injection. • Localized energy states through the 2.5 nm spacer impact carrier tunneling. • Carrier injection from quantum well to wetting-layer of SQDs, then loss to surface. • Facilitate SQD heterostructures to architect surface sensitive detection devices. This work exploits carrier injection hybrid structures in which carriers are injected into a layer of In 0.4 Ga 0.6 As surface quantum dots (SQDs) from an adjacent In 0.15 Ga 0.85 As quantum well (QW) as a function of spacer thickness from 10 nm down to 2.5 nm. Photoluminescence (PL) measurements verify that all such hybrid structures indeed have carriers collected into the QW and subsequently obtain an enhancement for PL intensity over that of the reference SQDs. The hybrid structure with the 2.5 nm spacer obtains the best carrier injection efficiency, due to the strongest coupling between the QW and the SQDs, while a thicker spacer results in less carrier injection from decreased quantum tunneling. However, the carrier injection is less efficient than expected. This is due to the fact that the QW confined energy states line up with the broad wetting layer (WL) energy states of SQDs of our test samples, leading to resonant carrier tunneling from the QW to the WL. Thus, there is significant carrier loss through tunneling into the WL of SQDs and then to surface states via nonradiative recombination. This characteristic must be considered in the design of surface sensitive detection devices using SQD injection structures. [ABSTRACT FROM AUTHOR]

This work investigates the temperature dependence of the performance of In(Ga)As-based solar cells made from sub-monolayer (SML) quantum dots (QDs), quantum wells (QWs), and Stranski-Krastanov QDs (SK-QDs). Well-defined sub-bandgap peaks are observed in external quantum efficiency (EQE) spectra for all samples. Apparently, changes in minority carrier lifetime affect both the sub-bandgap and the above bandgap EQE. Lateral confinement of carriers in the SMLs and QDs also affects the temperature dependence of the EQE. Finally, a "U" shaped curve was observed from the temperature dependence of the short-circuit current (I SC) from these nanostructure-based solar cells. This is due to the competition between the decreasing bandgap and the increasing carrier loss to recombination within the nanostructures as the temperature increases. In contrast, the solar cell's open-circuit voltage and power efficiency decrease monotonically with temperature. • Demonstrated novel Intermediate Band Solar Cell structure from sub-monolayer quantum dots. • Observed a 'U' shaped short-circuit current vs. temperature curve. • Demonstrated temperature dependence of external quantum efficiency of the sub-monolayer quantum dot solar cell. [ABSTRACT FROM AUTHOR]

Carrier dynamics including carrier relaxation and tunneling within a coupled InAs quantum dot (QD) – In 0.15 Ga 0.85 As quantum well (QW) hybrid nanostructure are investigated using photoluminescence (PL) spectroscopy. This coupled hybrid nanostructure shows a single PL peak from the QD emission at low excitation intensity and a band filling behavior is observed as the excitation intensity increases, suggesting that there exists a channel to capture carriers from the QW to the QDs. Time resolved PL (TRPL) measurements extract a carrier tunneling time of 103.7 ps, which is only one third of the theoretical prediction. A double-channel resonant carrier tunneling mechanism from the QW to the wetting layer and to the fifth excited state of the QDs and then carrier relaxation into lower discrete QD energy states is proposed to explain this fast carrier tunneling. The double-channel resonant carrier tunneling mechanism is qualitatively supported through the analysis of the excitation-dependent PL spectra as well as the PL excitation spectra. These results enrich our understanding of carrier dynamics in coupled QD and QW hybrid structures. [ABSTRACT FROM AUTHOR]

InAs(Sb)/GaAs self-assembled quantum dots (QDs) were grown by molecular beam epitaxy though incorporating Sb into InAs with increased beam equivalent pressure ratio, x = Sb 2 /(Sb 2 +As 2), of x = 0, 0.15, 0.25, and 0.5. From photoluminescence measurements, we observed a transition of the band alignment from type-I for the InAs QDs to type-II for InAsSb QDs. Thus, after adding Sb into the QDs these type II InAsSb QDs have different characteristics from the well-studied type-I InAs QDs regarding to their excitation intensity dependence, temperature dependence, and time dependence of the luminescence. Additionally, the Sb distribution in the QDs and the wetting layer was studied. These results indicate that we are able to fabricate InAsSb QDs with a type II band alignment, which may be good optical materials for the development of intermediate-band photovoltaic cells. • Self-assembled InAsSb quantum dots (QDs) are fabricated though incorporating Sb into InAs. • Band alignment transit to type-II for InAsSb QDs after adding Sb into InAs QDs. • Type-II luminescence for InAsSb QDs characterized by blue-shift and nonlinear decay of the emission. • High Sb-content in QDs than wetting layer. • More complex carrier dynamics and thermal quenching for InAsSb QDs. [ABSTRACT FROM AUTHOR]

The III-V nanowire quantum dots (NWQDs) monolithically grown on silicon substrates, combining the advantages of both one- and zero-dimensional materials, represent one of the most promising technologies for integrating advanced III-V photonic technologies on a silicon microelectronics platform. However, there are great challenges in the fabrication of high-quality III-V NWQDs by a bottom-up approach, that is, growth by the vapor-liquid-solid method, because of the potential contamination caused by external metal catalysts and the various types of interfacial defects introduced by self-catalyzed growth. Here, we report the defect-free self-catalyzed III-V NWQDs, GaAs quantum dots in GaAsP nanowires, on a silicon substrate with pure zinc blende structure for the first time. Well-resolved excitonic emission is observed with a narrow line width. These results pave the way toward on-chip III-V quantum information and photonic devices on silicon platform. [ABSTRACT FROM AUTHOR]

[Display omitted] • For the first time the InGaAs surface quantum dots (SQDs) are proposed to have type II photoluminescence characteristics. • Type II luminescence features are experimentally observed, including the blue shift of PL peak, the double exponential decay behavior, and a long carrier lifetime. • Due to Fermi level pinning, electrons are pinned at surface but holes are confined inside the SQDs, thus generating carrier separation and indirect transition. • It will help to develop sensors by using the surface-sensitive InGaAs SQDs. The In(Ga)As/GaAs surface quantum dots (SQDs) have become appealing recently due to the special surface sensitivity property and consequently the advantage in developing sensors for humidity detection. This research reveals that the InGaAs/GaAs single-layer SQDs exhibit carrier separation due to Fermi level pinning, where electrons are pinned at surface but holes are confined inside the SQDs. Thus, photoluminescence (PL) features corresponding to carrier indirect transition are observed through a prominent blue-shift of ∼ 31 meV for the PL band that obeys a cube root power law over four orders of magnitude change in excitation power. The indirect transition of these SQDs is further characterized through time-resolved PL studies showing a biexponential decay with a relatively elongated carrier lifetime of ∼ 1.35 ns. This is the first time that a concept of type-II characteristic is proposed for the InGaAs SQDs, which will help to optimize the design and working principles for developing sensors with surface-sensitive InGaAs SQDs. [ABSTRACT FROM AUTHOR]

The effect of different quantum structures in the intrinsic region of a pin junction solar cell (SC) on the optical and electrical properties have been investigated. SCs with different quantum structures, such as, Stranski-Krastanov (SK) quantum dots (QDs), quantum well (QW), submonolayer (SML) QDs (0.25 ML, 0.5 ML and 0.75 ML) and a quasi-monolayer (1 ML) InAs stack, were fabricated while keeping the total InAs content the same in all SCs. In a comparison of performance, the SML-QD sample delivered superior performance (Almost 23% relative efficiency improvement compared to reference SC) compared to the other devices. Moreover, different coverages of SML InAs have been tested for optimum performance improvement of solar cell and near 0.25 ML InAs deposition was found best for solar cell application. These findings present a promising alternative to SK-QDs as intermediate band in photovoltaic applications. • Effect of different quantum structures in the pin junction solar cell on its properties have been investigated. • Different coverages of submonolayer (SML) InAs have been tested for optimum performance improvement of solar cell. • Submonolayer InAs stack shows stronger confinement and the best external quantum efficiency for sub-bandgap photons. • 0.25 ML InAs deposition was found best and delivered superior solar cell performance compared to the other devices. • These findings present a promising alternative to SK-QDs as intermediate band in photovoltaic applications. [ABSTRACT FROM AUTHOR]

In(Ga)As surface quantum dots (SQDs) are promising candidates for surface-sensitive detection applications. As such, studies of the carrier dynamics are indispensable when attempting to understand both the physics and the device performances based on such SQD structures. Here, lateral carrier transfer among neighboring quantum dots (QDs) has been investigated through spectroscopic measurements for high density InGaAs/GaAs SQDs in a hybrid nanostructure with similar buried QDs (BQDs). Photoluminescence (PL) and temporal-resolved PL (TRPL) spectra demonstrate that the SQDs exhibit intra-layer exciton transfer and also strong carrier transfer to the surface states at 10 K. This imparts different optical characteristics to the SQDs with regards to the band filling and emission-energy-dependent carrier lifetime. In addition, PL excitation (PLE) spectra reveal a wetting layer absorption feature for the SQDs, which provides a channel for thermally activated carriers to transfer among the SQDs and to ultimately escape from the SQD layer. These investigations enrich our understanding of carrier dynamics for InGaAs SQDs, which may help to develop novel surface sensitive sensors. • Lateral intra-layer carrier transfer for high density InGaAs/GaAs QDs. • Carrier transfer due to electronic coupling and thermal activation among QDs. • Different band filling and carrier lifetime behaviors for buried and surface QDs. • PL excitation spectra reveal a wetting layer absorption for the surface QDs. • Wetting layer provides a possible channel for thermal activation of carriers for surface QDs. [ABSTRACT FROM AUTHOR]

InAs quantum dots (QDs) sandwiched inside a GaAsSb matrix possess advantages for achieving telecom wavelength lasers and for developing high efficiency solar cells. In this work, optical properties of InAs quantum dots (QDs) capped by GaAs 1-x Sb x (x = 0.11 and 0.15) are comparatively investigated. The photoluminescence measurements reflect that the energy state filling, thermal activation, quenching, and lifetime of the carriers in InAs/GaAs 0.89 Sb 0.11 QDs are different from those in the InAs/GaAs 0.85 Sb 0.15 QDs. These differences are attributed to the band alignment transition from type-I to type-II resulting from the Sb-composition change from x = 0.11 to x = 0.15 in the GaAs 1-x Sb x capping layer. Therefore, the emission and quenching involve excited states for type-I InAs/GaAs 0.85 Sb 0.15 QDs, but involve InAs QDs as well as the GaAs 0.85 Sb 0.15 QW recombination for type-II InAs/GaAs 0.85 Sb 0.15 QDs. So the luminescence reveals complex and distinct physics mechanisms for these two samples. • Photoluminescence (PL) for InAs quantum dots (QDs) capped by GaAs 1-x Sb x (x = 0.11 and 0.15). • Band alignment transition from type-I to type-II due to Sb-composition change from x = 0.11 to x = 0.15 in the GaAs 1-x Sb x layer. • Distinct energy state filling, thermal activation, quenching, and lifetime for carriers in the QDs. • PL reveals more complex and distinct physics mechanisms for InAs/GaAs 1-x Sb x QDs. [ABSTRACT FROM AUTHOR]