Three-dimensional Quantum Confinement Research Articles

Synergistic Steric Effect of Precursor And Antisolvent Enables Strongly Confined Perovskite Films with Efficient and Spectral Stable Blue Emission.

Reducing the crystal size of perovskites to the strong quantum confinement regime is an effective way to realize blue luminescence for light-emitting applications. However, challenges remain in directly constraining the crystal growth during film preparation to achieve three-dimensional quantum confinement, and the widely used long-chain ligands may bring difficulties for charge transport and unfavorably affect the device performance. Herein, we report a novel strategy for fabricating strongly confined blue-emitting perovskite nanocrystalline films via synergistic steric effect modulation by precursors and antisolvents. We synthesize cesium pentafluoropropanoate (CsPFPA) as a new type of precursor agent, where the steric effect of the PFPA group can help constrain the growth of perovskite crystals and passivate the defects. Furthermore, different types of antisolvents with varied molecular sizes and steric hindrance are used to regulate the size of perovskite crystals and improve film quality. Consequently, highly emissive blue perovskite films are realized with the emission wavelength effectively tuned in the blue region by varying the concentration of CsPFPA as well as the type of antisolvents. Based on the strongly confined perovskite films, blue light-emitting diodes (LEDs) are constructed, showing good spectral tunability and stability in the electroluminescence. This work demonstrates a novel pathway for developing bright perovskite blue emitters for LEDs, which may potentially advance their future applications in display and lighting.

Two-Dimensional CdSe-PbSe Heterostructures and PbSe Nanoplatelets: Formation, Atomic Structure, and Optical Properties.

Cation exchange enables the preparation of nanocrystals (NCs), which are not reachable by direct synthesis methods. In this work, we applied Pb2+-for-Cd2+ cation exchange on CdSe nanoplatelets (NPLs) to prepare two-dimensional CdSe-PbSe heterostructures and PbSe NPLs. Lowering the reaction temperature slowed down the rate of cation exchange, making it possible to characterize the intermediary NCs ex situ with atomically resolved high-angle annular dark-field scanning transmission electron microscopy and optical spectroscopy. We observe that the Pb2+-for-Cd2+ cation exchange starts from the vertices of the NPLs and grows into the zinc blende CdSe (zb-CdSe) lattice as a rock salt PbSe phase (rs-PbSe), while the anion (selenium) sublattice is being preserved. In agreement with previous works on CdTe-PbTe films, the interfaces between zb-CdSe and rs-PbSe consist of shared {001} and {011} planes. The final PbSe NPLs are highly crystalline and contain protrusions at the edges, which are slightly rotated, indicating an atomic reconfiguration of material. The growth of PbSe domains into CdSe NPLs could also be monitored by the emission peak shift as a function of the exchange time. Temperature-dependent emission measurements confirm a size-dependent change of the band gap energy with temperature and reveal a strong influence of the anisotropic shape. Time-resolved photoluminescence measurements between 4 and 30 K show a dark-bright exciton-state splitting different from PbSe QDs with three-dimensional quantum confinement.

Nonpolar Graphene Quantum Dot-Based Hydrophobic Coating from Microwave-Assisted Treatment of Styrofoam Waste

Graphene quantum dots (GQDs), one of the most promising nanoforms of carbon, have shown exceptional physiochemical properties owing to their strong three-dimensional quantum confinement. By altering the band gap or edge functionalization in GQDs, the properties can be tuned to meet challenging demands of modern computational and quantum devices. GQDs have primarily been synthesized at the lab scale so far, by both top-down and bottom-up approaches, using various natural or synthetic carbon-rich precursors. Only a few milligrams of the precursor is typically used in the synthesis, and it also involves hazardous acids, bases, or other catalysts, which impose additional time, labor, and cost for their removal. GQDs made hitherto are also functionalized with polar moieties due to the use of acids or bases in the synthesis, resulting in insolubility of GQDs in nonpolar solvents. Herein, an acid/base-free, microwave-assisted pyrolytic process is developed where GQDs of controlled size without any polar functionalities are synthesized using Styrofoam waste as the precursor. The structure of GQDs is confirmed by transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and other spectroscopic analysis, and it is found to be single layered with an average size of 5.5 ± 1.5 nm. A maximum yield of 15% is obtained by optimizing the pyrolysis temperature and exposure time of the precursor, and GQDs are found to be highly soluble in nonpolar solvents, including toluene and cyclohexane. The obtained GQDs were used as a promising agent to provide durable hydrophobicity and excellent self-cleaning property when coated on cotton fabric. The use of nonbiodegradable polymer waste such as Styrofoam to generate nonpolar GQDs of controlled dimensions provided a complete solution to not only curb deleterious effects of polymeric waste but also enable production of high value-added products for vast applications.

Photoluminescent Colloidal Nanohelices Self-Assembled from CdSe Magic-Size Clusters via Nanoplatelets.

Reports on photoluminescent colloidal semiconductor two-dimensional (2D) helical nanostructures with one-dimensional quantum confinement are relatively rare. Here, we discuss the formation of such photoluminescent nanostructures for CdSe. We show that when as-synthesized unpurified zero-dimensional (0D) CdSe magic-size clusters (MSCs) (passivated by carboxylate ligands with three-dimensional quantum confinement) are dispersed in a solvent (such as toluene or chloroform) containing hexadecylamine and then subjected to sonication, helical nanostructures are obtained, as observed by transmission electron microscopy. We demonstrate that the formation involves the self-assembly of 0D MSCs into 2D nanoplatelets, which act as intermediates. The CdSe MSCs and their self-assembled 2D nanostructures display almost identical static optical properties, namely, a sharp absorption doublet with peaks at 433 and 460 nm and a narrow emission peak at 465 nm; this is a subject for further study. This study introduces new methods for fabricating photoluminescent helical nanostructures via the self-assembly of photoluminescent MSCs.

Cadmium selenide quantum dots: Synthesis, characterization and their humidity and temperature sensing properties with poly-(dioctylfluorene)

In this paper, we report synthesis, thin film characteristics and sensing properties of cadmium selenide (CdSe) quantum dots (QDs) for enhancing the humidity and temperature sensing of a polymeric semiconductor poly-(9,9-di-n-octylfluorenyl-2,7-diyl) (F8). Transmission electron microscopy (TEM) has been performed to study the texture, distribution over surface and size of the synthesized CdSe QDs. TEM image revealed slightly non-uniform distribution of the QDs with an average size of 4 nm having three-dimensional quantum confinement features. Atomic force microscopy (AFM) is carried out to investigate the average grain size and surface roughness of the F8-CdSe nanocomposite film. To understand the role of CdSe QDs on the sensing properties of F8, a blend F8-CdSe QDs has been prepared at 10:1 wt-percent (wt%) of F8 and CdSe QDs, respectively, in chloroform. An Ag/F8-CdSe QDs/Ag surface-type sensor has been fabricated via spin coating F8-CdSe QDs nanocomposite on a 45 μm gap between the pre-patterned silver (Ag) electrodes on glass substrate. The fabricated Ag/F8-CdSe QDs/Ag sensor has been studied for humidity and temperature sensing by measuring capacitance (C) of the sensor as a function of humidity and temperature, respectively. The Ag/F8-CdSe QDs/Ag sensor exhibits enhancement in the sensing parameters such as response time and recovery time i.e., 9 s and 7 s, respectively, as compared to our previously studied Ag/F8/Ag sensor whose response and recovery time were 15 s and 7 s, respectively. This improvement is due to the addition of CdSe QDs in F8 polymer matrix which changes some of the important properties of the F8-CdSe QDs nanocomposite such as electron polarizability, polarity, hydrophobicity and size dependent properties. The role of porosity (P) in the sensing properties of the active film of Ag/F8-CdSe QDs/Ag device has also been explored. The Ag/F8-CdSe QDs/Ag based sensor shows approximately linear change in C as a function of humidity and temperature with wide range of sensitivity from 25 percent relative humidity (%RH) to 90%RH and from 16 to 186 °C, respectively.

Parametric analysis of mechanically driven compositional patterning in SiGe substrates

A recently demonstrated approach for creating structured compositional gradients in the near-surface region of SiGe substrates is studied parametrically using a multiresolution coarse-grained lattice kinetic Monte Carlo simulation method. In the “stress patterning” process, a patterned elastic stress field is generated in the SiGe substrate by pressing an array of micro-indenters into it. The stressed substrate is then thermally annealed to drive the atomic diffusion in which the larger Ge atoms are pushed away from the areas of compressive stress. By varying a subset of the parameters that characterize the high-dimensional input space of the process (e.g., indenter spacing, indenter tip shape, and indenter array symmetry) we show that technologically interesting compositional configurations may be readily generated. In particular, we show that it is theoretically possible to generate arrays of well-delineated nanoscale regions of high Ge content surrounded by essentially pure Si. Such configurations may be useful as Ge “quantum dots” that exhibit three-dimensional quantum confinement, which have otherwise been very challenging to create with high degrees of size and spatial uniformity. These simulation results will be instrumental in guiding future experimental demonstrations of stress patterning.

Temperature independent infrared responsivity of a quantum dot quantum cascade photodetector

We demonstrate a quantum dot quantum cascade photodetector with a hybrid active region of InAs quantum dots and an InGaAs quantum well, which exhibited a temperature independent response at 4.5 μm. The normal incident responsivity reached 10.3 mA/W at 120 K and maintained a value of 9 mA/W up to 260 K. It exhibited a specific detectivity above 1011 cm Hz1/2 W−1 at 77 K, which remained at 108 cm Hz1/2 W−1 at 260 K. We ascribe the device's good thermal stability of infrared response to the three-dimensional quantum confinement of the InAs quantum dots incorporated in the active region.

Effects of N Incorporation on Carrier Recombination in GaAs-Based Nanowires Grown By Molecular Beam Epitaxy on Si Substrates

III-V semiconductor nanowires (NWs) such as GaAs NWs form an interesting artificial materials system promising for applications in advanced optoelectronic and photonic devices, thanks to the advantages offered by the one dimensional architecture and the possibility to combine it with the main-stream silicon technology. Alloying of GaAs with nitrogen can further enhance performance and extend device functionality via band-structure and lattice engineering. However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality. The contribution of the surface-related recombination is known to be especially severe in GaAs-based NW structures due to a large surface-to-volume ratio and the presence of surface states participating in the non-radiative recombination processes. In this work we employ photoluminescence (PL) transient spectroscopy to study exciton and free carrier recombination dynamics in novel GaAs/GaNAs core/shell NWs grown by plasma-assisted molecular beam epitaxy (MBE) on (111) plane Si substrates. It is shown that the PL emission in these structures is dominated by radiative recombination of localized excitons (LE) at T< 100 K and free exciton/carriers at T > 100K, both of which occur within the GaNAs shell. The LE dynamics is found to be determined by their energy transfer from shallow to deep localized states and also radiative recombination. The latter has a typical lifetime of around 5 ns and predominantly governs transient behavior of the deeply localized excitons. The fact that this radiative lifetime is insensitive to measurement temperature could suggest that the deeply localized states within the GaNAs alloy experience three-dimensional quantum confinement. On the other hand, PL decay arising from FE/free carriers that dominates at T>100K is found to be significantly faster and is governed by nonradiative recombination which occurs predominantly within the near-surface region of the GaNAs shell. The contribution of the surface recombination, which shortens the exciton lifetime down to tens of picoseconds, is concluded to be enhanced in the NW structures with a higher surface-to-volume ratio. This conclusion is based on the comparison of exciton dynamics in the NW structures with that in the reference GaNAs epilayer. Most importantly, the surface recombination becomes partially suppressed with increasing nitrogen composition in the alloy. This conclusion is based on our experimental finding that lifetimes of photo-generated free excitons and free carriers increase with increasing N composition - see Figure 1. This is accompanied by a sizable enhancement in the room temperature PL intensity in the GaAs/GaNAs core/shell NWs as compared with reference GaAs NW structures. The observed N-induced suppression of the surface recombination is suggested to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination. Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters grown on Si substates, which offers a number of attractive added values such as large freedom in band and lattice engineering as well as inherent passivation of harmful surface states. Figure 1

(Invited) Electrically Pumped Lasers and Light Emitting Diodes in the Ultraviolet-C Band with AlGaN Nanowires

Ultraviolet (UV) light sources, including light emitting diodes (LEDs) and lasers, with emission wavelengths less than 280 nm (UV-C band) are critically important for a wide range of applications including water purification, disinfection, data storage, medical diagnosis, and bio/chemical sensing. To date, the development of such light sources with aluminum gallium nitride (AlGaN) has been severely limited by the presence of large dislocation densities and the extremely inefficient p-type doping. In addition, the intrinsic TM light polarization of Al-rich AlGaN prohibits the light extraction from conventional c-plane wurtzite structures. In this context, we have investigated the molecular beam epitaxial (MBE) growth and characterization of nearly defect-free AlGaN nanowires on Si. We have demonstrated, for the first time, electrically injected lasers in the UV-C band, which exhibit a threshold current density of 0.2 kA/cm2. By exploiting the efficient light scattering among nanowire arrays, we have also demonstrated high efficiency AlN nanowire LEDs with emission wavelength ~ 207 nm. In this experiment, the AlGaN nanowires were spontaneously formed on Si substrate by radio-frequency plasma-assisted MBE without using any foreign metal catalyst. The laser device structure consisted of n-GaN contact layer, n-AlGaN cladding layer, AlGaN active region, p-AlGaN cladding layer, and p-GaN contact layer. The optical cavity was formed by the Anderson localization of light, due to the recurrent multiple scattering of photons in random nanowire arrays. The fabrication process involved standard optical lithography and contact metallization techniques. The lasers operated under continuous wave (CW) biasing conditions. The electroluminescence emission was collected from the device top surface by a CCD camera coupled to a high-resolution spectrometer. A lasing peak around 262 nm was clearly measured at 77 K, with a threshold current density of 0.2 kA/cm2. This is the first demonstration of electrically injected semiconductor lasers in the deep UV wavelength range. Detailed studies further showed that the self-organized AlGaN nanowires exhibited extensive atomic scale compositional modulation. The extremely low threshold current is directly related to the three-dimensional quantum confinement of charge carriers by the quantum dot/dash-like nanostructures in nearly defect-free AlGaN nanowires. We have further investigated deep UV LEDs based on self-organized AlGaN nanowires. In this study, the device structure consisted of n-GaN contact layer, n-Al(Ga)N, i-Al(Ga)N, p-Al(Ga)N, and p-(Al)GaN contact layers. Strong electroluminescence at 207 nm was measured at room-temperature from LEDs fabricated with AlN. Furthermore, detailed angle dependent electroluminescence studies indicated that the dominant light emission direction was from the c-axially grown nanowire top surface, due to the efficient light scattering amongst nanowires, in spite of TM light polarization in AlN. Moreover, an electrical efficiency of > 85% was realized from such AlN nanowire LEDs, which can be largely ascribed to the hole hopping conduction in the impurity band hopping. In addition, our detailed studies further indicated that the performance of AlN nanowire LEDs was largely limited by electron overflow.

Three-Dimensional Quantum Confinement of Charge Carriers in Self-Organized AlGaN Nanowires: A Viable Route to Electrically Injected Deep Ultraviolet Lasers.

We report on the molecular beam epitaxial growth and structural characterization of self-organized AlGaN nanowire arrays on Si substrate with high luminescence efficiency emission in the deep ultraviolet (UV) wavelength range. It is found that, with increasing Al concentration, atomic-scale compositional modulations can be realized, leading to three-dimensional quantum confinement of charge carriers. By further exploiting the Anderson localization of light, we have demonstrated, for the first time, electrically injected AlGaN lasers in the deep UV band operating at room temperature. The laser operates at ∼289 nm and exhibits a threshold of 300 A/cm(2), which is significantly smaller compared to the previously reported electrically injected AlGaN multiple quantum well lasers.

Investigation of the shape of submonolayer quantum dots using a polarization-dependent photocurrent

Structural and optical characterization of multi-stack InAs/InGaAs submonolayer quantum dots (SML-QDs) grown under the Stranski–Krastanov growth mode was performed via a polarization-dependent study. Various angular in-plane (plane perpendicular to growth direction) and out-of-plane (plane parallel to the 45°-polished facet) polarization-dependent spectral photocurrents were measured to investigate the three-dimensional quantum confinement in multi-stack 0.3 monolayer InAs SML-QDs (the shape of SML-QDs embedded in an SML-QD based photodetector). Scanning transmission electron microscopy images revealed the interdiffusion of indium atoms between SML-QDs and the InGaAs quantum well due to an insufficient amount of indium, which agrees well with the tendency of s- to z-polarized response ratios.

An electrically injected AlGaN nanowire laser operating in the ultraviolet-C band

We have investigated the molecular beam epitaxial growth and characterization of nearly defect-free AlGaN nanowire heterostructures grown directly on Si substrate. By exploiting the Anderson localization of light, we have demonstrated electrically injected AlGaN nanowire lasers that can operate at 262.1 nm. The threshold current density is 200 A/cm2 at 77 K. The relatively low threshold current is attributed to the high Q-factor of the random cavity and the three-dimensional quantum confinement offered by the atomic-scale composition modulation in self-organized AlGaN nanowires.

CdS:PMMA nanocomposite solid films with enhanced properties

Size tunability and enhanced optical properties of cadmium sulphide (CdS) nanoparticles entrapped in polymethyl methacrylate (PMMA) matrix were presented in this paper. The three-dimensional quantum confinement of CdS in the PMMA matrix was achieved by the in situ technique. X-ray diffraction results show the presence of CdS in the PMMA matrix for higher concentration of CdS nanoparticles (1:20). The particle size and energy band gap were determined by UV–visible spectroscopy. The photoluminescence spectrum shows broadened surface trapped emissions that are shifted towards the blue region. The formation of CdS and its stoichiometric ratio has been confirmed using X-ray photoelectron spectroscopy. The transmission electron microscope results reveal the uniform distribution of nanometre sized particles in the PMMA matrix. The size distribution of CdS nanoparticles in the nanocomposite was carried out by atomic force microscope.

Excitons and biexcitons in InGaN quantum dot like localization centers

Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross-section transmission electron microscopy reveals varying shapes and lateral sizes in the range ∼1–5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to −22 meV, in correlation with the exciton emission energy. Negative binding energies are only justified by a three-dimensional quantum confinement, which confirms QD-like properties of the localization centers. The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ∼3 nm for a QD with strongly negative Ebxx = −15.5 meV.

A Simple ZnO Nanocrystal Synthesis Illustrating Three-Dimensional Quantum Confinement

Semiconductor nanocrystals or “quantum dots” are attractive materials for exploring quantum confinement effects. For example, band-gap energies of these materials depend on particle size, and this dependence can be explained using simple, quantum mechanical models. We outline here an undergraduate physical chemistry laboratory involving the room-temperature synthesis and absorption spectroscopy of ZnO nanocrystals. The experimental results are compared with the predictions of a three-dimensional quantum confinement (or “particle-in-a-sphere”) model. The ease of synthesis and data collection, the common precursors employed, and the simple spectroscopic analysis allow facile incorporation of this experiment into essentially any undergraduate laboratory program.

InAs Quantum Dots on Nanopatterned GaAs (001) Surface: The Growth, Optical Properties, and Device Implementation

This work reviews the growth, optical properties, and device implementation of InAs semiconductor quantum dots (QDs) selectively nucleated atop nano-faceted GaAs pyramidal structures grown by metal-organic chemical-vapor deposition. This site-controlled QD growth technique offers unique features and benefits subsequent device applications. First, GaAs pyramids, formed on a SiO2-masked and nanopatterned (001) GaAs substrate, are characterized by well-defined equilibrium crystal shapes (ECS). The controlled ECS formation is crucial to subsequent patterned QD (PQD) nucleation, which is highly preferential toward {11n} planes due to superior QD energy minimization. Second, PQD optical properties are thoroughly studied by monitoring room temperature (RT) photoluminescence (PL) and power-dependent low-temperature PL to verify the crystalline quality and the three-dimensional quantum confinement. The PQD ensembles formed on different GaAs pyramids, with different PL behavior, indicate lateral coupling within QD clusters and characteristics of isolated QD pairs. Then, PQDs embedded in a InGaAs quantum well, the so-called dot-in-the-well (DWELL) structure, are compared to a self-assembled QD (SAQD) DWELL structure, and shown to have a better emission efficiency, due to the distributed QW thickness profile on the faceted GaAs pyramid. Finally, broad-area light emitting diodes based on the PQD active region are fabricated. Linear current-voltage characteristics are observed with sharp turn-on, low leakage current and low forward resistance. Electroluminescence spectra show PQD intraband structure and low quenching of emission from 77 K to room temperature. Light-current measurements demonstrate external quantum efficiency per PQD comparable to SAQDs, despite the two regrowth steps in the fabrication processes.

Quantum dot lasers: From promise to high-performance devices

Ever since self-organized In(Ga)As/Ga(AI)As quantum dots were realized by molecular beam epitaxy, it became evident that these coherently strained nanostructures could be used as the active media in devices. While the expected advantages stemming from three-dimensional quantum confinement were clearly outlined, these were not borne out by the early experiments. It took a very detailed understanding of the unique carrier dynamics in the quantum dots to exploit their full potential. As a result, we now have lasers with emission wavelengths ranging from 0.7 to 1.54 μm, on GaAs, which demonstrate ultra-low threshold currents, near-zero chip and α-factor and large modulation bandwidth. State-of-the-art performance characteristics of these lasers are briefly reviewed. The growth, fabrication and characteristics of quantum dot lasers on silicon substrates are also described. With the incorporation of multiple quantum dot layers as a dislocation filter, we demonstrate lasers with J th=900 A/cm 2. The monolithic integration of the lasers with guided wave modulators on silicon is also described. Finally, the properties of spin-polarized lasers with quantum dot active regions are described. Spin injection of electrons is done with a MnAs/GaAs tunnel barrier. Laser operation at 200 K is demonstrated, with the possibility of room temperature operation in the near future.

Enhanced Thermopower in PbSe Nanocrystal Quantum Dot Superlattices

We examine the effect of strong three-dimensional quantum confinement on the thermopower and electrical conductivity of PbSe nanocrystal superlattices. We show that for comparable carrier concentrations PbSe nanocrystal superlattices exhibit a substantial thermopower enhancement of several hundred microvolts per Kelvin relative to bulk PbSe. We also find that thermopower increases monotonically as the nanocrystal size decreases due to changes in carrier concentration. Lastly, we demonstrate that thermopower of PbSe nanocrystal solids can be tailored by charge-transfer doping.

Quantum-Dot Optoelectronic Devices

Self-organized In(Ga)As/Ga(Al)As quantum dots have emerged as useful nanostructures that can be epitaxially grown and incorporated in the active region of devices. The near pyramidal dots exhibit properties arising from the three-dimensional quantum confinement and from the coherent built-in strain. The properties and current state-of-the-art characteristics of quantum-dot junction lasers, intersublevel infrared detectors, optical amplifiers, and microcavity devices are briefly reviewed. It is evident that self-organized quantum-dot optoelectronic devices demonstrate properties that are sometimes unique and often surpass the characteristics of existing devices.

High-Temperature Tunneling Quantum-Dot Intersublevel Detectors for Mid-Infrared to Terahertz Frequencies

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Quantum-dot infrared photodetectors have emerged as attractive devices for sensing long wavelength radiation. Their principle of operation is based on absorption of radiation via intersublevel transitions in quantum dots. Multiple layers of self-organized In(Ga)As/Ga(Al)As quantum dots are generally incorporated in the active region of these devices. Three-dimensional quantum confinement allows normal incidence operation. This paper describes a novel variation in the design of these devices which allows a significant reduction of the dark current, high temperature operation and extension of operation to terahertz frequencies. The principle of operation and operating characteristics of this device—the tunnel quantum-dot intersublevel detector—are described. Operation is demonstrated from 6–80 <formula formulatype="inline"><tex>$\mu{\hbox {m}}$</tex></formula> at temperatures up to 300 K with acceptable values of peak responsivity (0.1–0.75 A/W) and specific detectivity ( <formula formulatype="inline"><tex>$\hbox{10}^{7}$</tex></formula>–<formula formulatype="inline"><tex>$ \hbox{10}^{11}\ {\hbox {cm}}\cdot \hbox{Hz}^{1/2}/ \hbox{W}^{-1}$</tex></formula>, depending on temperature and wavelength). </para>