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In classical Cauchy elasticity, 3D materials exhibit six eigenmodes of deformation. Following the 1995 work of Milton and Cherkaev, extremal elastic materials can be classified by the number of eigenmodes, N, out of these six that are “easy”. Using Greek number words, this leads to hexamode (N = 6), pentamode (N = 5), tetramode (N = 4), trimode (N = 3), dimode (N = 2), and monomode (N = 1) materials. While hexamode materials are unstable in all regards, the possibility of pentamode metamaterials (“meta-fluids”) has attracted considerable attention throughout the last decade. Here, inspired by the 2021 theoretical work of Wei, Liu, and Hu, microstructured 3D polymer-based tetramode metamaterials are designed and characterized by numerical band-structure calculations, fabricated by laser printing, characterized by ultrasound experiments, and compared to the theoretical ideal. An application in terms of a compact and broadband polarizer for acoustical phonons at ultrasound frequencies is demonstrated.

At Photonics West 2020, we reported progress on rapid multi-focus multi-photon 3D laser printing, enabling printing rates of up to ten million voxels/s at voxel sizes of about 400 nm (mean of lateral and axial extent). Meanwhile, we have refined and improved this setup. Here, we present three-dimensional chiral mechanical metamaterials with tailorable characteristic length as a scientific application. The characteristic length is as large as 10 unit cells. The largest 3D printed samples have a side length of 27 unit cells, corresponding to 118,098 unit cells total. Our experimental findings are in good qualitative agreement with modeling.

To enable graphene-integrated interconnects in modern VLSI circuits, a major roadblock is developing an efficient Back End of Line (BEOL) compatible doping technique. In this paper, we demonstrate metal-induced doping of graphene in graphene-ruthenium hybrid structures. We study doping by systematically performing different material characterization techniques – Internal Photoemission Spectroscopy (IPE), Raman Spectroscopy and Kelvin Probe Force Microscopy (KPFM) to gain a deeper understanding on the charge transfer at the graphene-Ru interface. In IPE, we measure the relative band alignment of graphene and Ru, the interface potential barrier and effective work function of 4.9eV. With Raman spectral mapping, we report p-type doping in single layer graphene on Ru film with carrier density 1.9E13cm−2. And with KPFM, Fermi-level shift of ∼420 meV (wrt intrinsic graphene) is observed implying downward shift of Fermi level in the graphene valence band. Electrically, graphene capping results in ∼19 % drop in sheet resistance of Ru accompanied by significant decrease in contact resistance. Moreover, the temperature coefficient of resistance reduces after graphene capping indicating better response to thermal fluctuations. By performing an extensive study using different material and electrical techniques, our results provide a viable and practical basis for integrating graphene as a conductor in advanced interconnects.

To further understand the interaction of graphene-integrated interconnects, we focus on the interface characterization of graphene-ruthenium hybrid systems. A systematic characterization is performed to quantify the charge transfer between graphene and Ru. By studying the relative band alignment, we measure interface potential barrier height and report an effective work function of 4.9 eV. Carrier concentration of 1.9E13cm−2 is obtained. Surface potential mapping suggests a downward shift of Fermi level in graphene valence band implying hole-doping on Ru substrate. Concurrent physical characterizations complement each other and fully support the conductivity gain demonstrated earlier.

Two-dimensional transition metal dichalcogenides have been the focus of intense research for their potential application in novel electronic and optoelectronic devices. However, growth of large area two-dimensional transition metal dichalcogenides invariably leads to the formation of grain boundaries that can significantly degrade electrical transport by forming large electrostatic barriers. It is therefore critical to understand their effect on the electronic properties of two-dimensional semiconductors. Using MoS

To keep Moore's law alive, 2D materials are considered as a replacement for Si in advanced nodes due to their atomic thickness, which offers superior performance at nm dimensions. In addition, 2D materials are natural candidates for monolithic integration which opens the door for density scaling along the 3rd dimension at reasonable cost. This paper highlights the obstacles and paths to a scaled 2D CMOS solution. The baseline requirements to challenge the advanced Si nodes are defined both with a physical compact model and TCAD analysis, which allows us to identify the most promising 2D material and device design. For different key challenges, possible integrated solutions are benchmarked and discussed. Finally we report on the learning from our first lab to fab vehicle designed to bridge the lab and IMEC's 300mm pilot line.

We report on the experimental observation of a cyclotron antiresonance in a canonical 3D topological insulator Bi$_2$Te$_3$. Magneto-reflectance response of single crystal Bi$_2$Te$_3$ was studied in 18 Tesla magnetic field, and compared to other topological insulators studied before, the main spectral feature is inverted. We refer to it as an antiresonance. In order to describe this unconventional behavior we propose the idea of an imaginary cyclotron resonance frequency, which on the other hand indicates that the form of the Lorentz force that magnetic field exerts on charge carriers takes an unconventional form.

The Zeeman splitting and degree of circular polarization (DCP) of photoluminescence (PL) from type-II submonolayer ZnTe/ZnSe quantum dots (QDs) have been investigated in magnetic fields up to 18 T. To explain the observed relative intensities and energy positions of the σ+ and the σ− PL, a non-Boltzmann distribution for holes with ultra-long spin-flip time, confined to submonolayer QDs, is proposed. The g-factor of electrons, located in the ZnSe barriers, was obtained from fitting the temperature dependence of the DCP, and its value is in excellent agreement with that of bulk ZnSe. The g-factor of type-II excitons was extracted by analyzing the Zeeman splitting, from which the g-factor of holes confined within submonolayer ZnTe QDs was found to be ∼2.65 ± 0.40. This value is considerably larger than that in bulk ZnTe. Tight-binding calculations using an sp3s* model were employed to understand the origin of such an increase. The results of the simulation match the experiment and show that the enhancement of the hole g-factor is mostly caused by a reduced orbital contribution to Zeeman splitting arising from the submonolayer thickness of these QDs.The Zeeman splitting and degree of circular polarization (DCP) of photoluminescence (PL) from type-II submonolayer ZnTe/ZnSe quantum dots (QDs) have been investigated in magnetic fields up to 18 T. To explain the observed relative intensities and energy positions of the σ+ and the σ− PL, a non-Boltzmann distribution for holes with ultra-long spin-flip time, confined to submonolayer QDs, is proposed. The g-factor of electrons, located in the ZnSe barriers, was obtained from fitting the temperature dependence of the DCP, and its value is in excellent agreement with that of bulk ZnSe. The g-factor of type-II excitons was extracted by analyzing the Zeeman splitting, from which the g-factor of holes confined within submonolayer ZnTe QDs was found to be ∼2.65 ± 0.40. This value is considerably larger than that in bulk ZnTe. Tight-binding calculations using an sp3s* model were employed to understand the origin of such an increase. The results of the simulation match the experiment and show that the enhancement o...

Recently, Weyl semimetals have been experimentally discovered in both inversion-symmetry-breaking and time-reversal-symmetry-breaking crystals. The non-trivial topology in Weyl semimetals can manifest itself with exotic phenomena, which have been extensively investigated by photoemission and transport measurements. Despite the numerous experimental efforts on Fermi arcs and chiral anomaly, the existence of unconventional zeroth Landau levels, as a unique hallmark of Weyl fermions, which is highly related to chiral anomaly, remains elusive owing to the stringent experimental requirements. Here, we report the magneto-optical study of Landau quantization in Weyl semimetal NbAs. High magnetic fields drive the system toward the quantum limit, which leads to the observation of zeroth chiral Landau levels in two inequivalent Weyl nodes. As compared to other Landau levels, the zeroth chiral Landau level exhibits a distinct linear dispersion in magnetic field direction and allows the optical transitions without the limitation of zero z momentum or \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sqrt B$$\end{document}B magnetic field evolution. The magnetic field dependence of the zeroth Landau levels further verifies the predicted particle-hole asymmetry of the Weyl cones. Meanwhile, the optical transitions from the normal Landau levels exhibit the coexistence of multiple carriers including an unexpected massive Dirac fermion, pointing to a more complex topological nature in inversion-symmetry-breaking Weyl semimetals. Our results provide insights into the Landau quantization of Weyl fermions and demonstrate an effective tool for studying complex topological systems., How the carriers behave in a Weyl semimetal if they occupy the lowest Landau level remains elusive. Here, the authors report evidences of electrons occupying zeroth chiral Landau levels with distinct linear dispersion behaviors for two inequivalent Weyl nodes in a Weyl semimetal NbAs.

We present magnetooptical and transport properties of metamorphic periodic structures containing InAsSb layers with controllable modulated Sb composition [1]. The modulation period is determined by the thicknesses of the strain compensated InAsSbx/InAsSby pairs grown on a virtual AlGaInSb substrate with a lattice constant of 6.25 A. We demonstrate that the bandgap energy of ordered InAsSb0.3/InAsSb0.75 alloy varies from 100mev to a few meV as a result of the well-regulated variation of the modulation period from ∼3 to ∼7.5 nm. The material effective masses and the specific character of the energy spectra will be discussed. 1. G. Belenky, Y. Lin, L. Shterengas, D. Donetsky, G. Kipshidze and S. Suchalkin, Electron. Lett. 51 (19), 1521, (2015)

Inflammatory arthritis is a group of diseases which can lead to a variety of characteristic orthopedic conditions, including deformity, tendon rupture, and joint destruction. Although the use of disease-modifying antirheumatic drugs (DMARDs) has significantly decreased the need for surgery among patients with inflammatory arthritis, there is still a role for the orthopedic surgeon in management of these diseases. Surgical treatment includes a variety of procedures to reduce pain and improve function and appearance.

Two-dimensional transition metal dichalcogenides have been the focus of intense research for their potential application in novel electronic and optoelectronic devices. However, growth of large area two-dimensional transition metal dichalcogenides invariably leads to the formation of grain boundaries that can significantly degrade electrical transport by forming large electrostatic barriers. It is therefore critical to understand their effect on the electronic properties of two-dimensional semiconductors. Using MoS2 as an example material, we are able to probe grain boundaries in top and buried layers using conductive atomic force microscopy. We find that the electrical radius of the grain boundary extends approximately 2 nm from the core into the pristine material. The presence of grain boundaries affects electrical conductivity not just within its own layer, but also in the surrounding layers. Therefore, electrical grain size is always smaller than the physical size, and decreases with increasing thickness of the MoS2. These results signify that the number of layers in synthetically grown 2D materials must ideally be limited for device applications.

It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 106 m s−1 remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe., Kane fermions are predicted to be tunable with external parameters such as temperature. Here, Teppe et al. show a band structure evolution of bulk HgCdTe as temperature is tuned across topological phase transition, demonstrating that Kane fermions change sign in rest-mass and remain constant in velocity.

The rapid cadence of MOSFET scaling is stimulating the development of new technologies and accelerating the introduction of new semiconducting materials as silicon alternative. In this context, 2D materials with a unique layered structure have attracted tremendous interest in recent years, mainly motivated by their ultra-thin body nature and unique optoelectronic and mechanical properties. The development of scalable synthesis techniques is obviously a fundamental step towards the development of a manufacturable technology. Metal-organic chemical vapor deposition has recently been used for the synthesis of large area TMDs, however, an important milestone still needs to be achieved: the ability to precisely control the number of layers and surface uniformity at the nano-to micro-length scale to obtain an atomically flat, self-passivated surface. In this work, we explore various fundamental aspects involved in the chemical vapor deposition process and we provide important insights on the layer-dependence of epitaxial MoS2 film's structural properties. Based on these observations, we propose an original method to achieve a layer-controlled epitaxy of wafer-scale TMDs.

The rapid cadence of MOSFET scaling is stimulating the development of new technologies and accelerating the introduction of new semiconducting materials as silicon alternative. In this context, transition metal dichalcogenides (TMDs) with a unique layered structure have attracted tremendous interest in recent years mainly motivated by the characteristic 2D nature together with distinctive and tunable optoelectronic properties which make them appealing for a wide variety of applications. Their ultra-thin body nature, in particular, is expected to provide superior immunity to short channel effects therefore extending the potential to scale transistors down to the few-nanometer-scale. [1-4] Another key feature of 2D materials is the absence of surface dangling bonds. The latter property has the potential to eliminate lattice mismatch constraints thus paving the way for hybrid integration of TMDs into artificial heterostructures with sharp interfaces and designed band alignment. As researchers explore the physics and applications of layered semiconductors, it is now becoming important to find a wafer-scale path towards technology implementation and integration of these novel materials. In this context, it has been recently demonstrated that metal-organic chemical vapor deposition (MOCVD) can be used to manufacture large area 2D semiconductor materials. [5]. The goal of this work is to unravel some of the fundamental aspects of film formation and provide a pathway towards a layer-controlled, wafer-scale synthesis of TMD films. More in details, we will provide insights on the different growth mechanisms of TMD films on amorphous and crystalline templates. In this framework, we will discuss the key aspects to enable and control a real van der Waals epitaxy of TMD films. The target, of course, is to achieve unidirectional and high quality monocrystalline domains by forcing an epitaxial relationship between the 2D film and the underlying substrate. In-depth structural AFM, XPS, TEM analyses along with Raman, Photoluminescence and lifetime measurements are used in our study. In order to establish a direct link between electrical performance and material quality, FET devices using our layers are also fabricated. A careful link between the structural analyses and the electrical results is made in order to asses material quality and offer a step further on the understanding of 2D TMDs for nanoelectronics. B. Radisavljevic et al. Nature Nanotechnol., 6, 147 (2011). R. Ganatra and Q. Zhang, ACS Nano, 8, 4074 (2014). A. Nourbakhsh et al. Nano Lett., 16 7798 (2016). A. Nourbakhsh et al. Nanoscale, 18, 6122 (2017). K. Kang et al. Nature volume 520, 656 (2015)

The rapid cadence of MOSFET scaling is stimulating the development of new technologies and accelerating the introduction of new semiconducting materials as silicon alternative. In this context, transition metal dichalcogenides (TMDs) with a unique layered structure have attracted tremendous interest in recent years mainly motivated by the characteristic 2D nature together with distinctive and tunable optoelectronic properties which make them appealing for a wide variety of applications. Their ultra-thin body nature, in particular, is expected to provide superior immunity to short channel effects therefore extending the potential to scale transistors down to the few-nanometer-scale. [1-4] Another key feature of 2D materials is the absence of surface dangling bonds. The latter property has the potential to eliminate lattice mismatch constraints thus paving the way for hybrid integration of TMDs into artificial heterostructures with sharp interfaces and designed band alignment. These ingredients, as recently demonstrated, make TMDs ideal building blocks for the fabrication of tunnel field effect transistors with very steep sub-threshold slope which is mandatory for low voltage device operation. [5] Based on these premises, there are some practical issues that need to tackled in order to enable a TMD-based technology. Given their 2D nature, the electronic properties of TMDs critically depend on the physico-chemical characteristics of the interfaces. Therefore, interface/surface engineering represents a logical route to control the electrical performance of TMD-based devices. Surface quality control is mainly a material growth-related issue. From that standpoint, the development of scalable synthesis techniques is obviously a fundamental step towards the development of a manufacturable technology. However, another important step still needs to be achieved: the ability to precisely control the number of layers and surface uniformity at the nano-to micro-length scale over the entire wafer surface to obtain TMD films with atomically flat, self-passivated surfaces. This challenge is further complicated by the fact that powder vaporization techniques and CVD processes used to grow TMD films do not exhibit a self-limiting character. Because of that, local thickness fluctuations and layer discontinuities are commonly observed in synthetic TMD films. In this work, we will discuss fundamental aspects of film formation and provide a pathway towards layer-controlled, wafer-scale synthesis of TMD films. The high temperatures involved in the synthesis process as well as the use of growth templates require the development of a reliable wafer-scale transfer technology. Such a heterogeneous integration, on the one hand, is useful to overcome the incompatibility of the growth process with processing requirements for the BEOL interconnect structures. On the other hand, it reduces the level of control over the interface between the 2D layer and the dielectric substrate. It is not surprising that electronic transport in transferred TMD films is strongly affected by hydrocarbon residues, non-homogeneities (e.g. uncontrolled strain and contaminated regions), dipole formation, and charge transfer effects. Monitoring environmental effects in ultra-thin TMD films and minimizing the impact of layer transfer on the electrostatic potential distribution across the interface is of utmost importance. A wafer-scale transfer process and related experimental challenges and opportunities will be also presented. B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, Nature Nanotechnol., 6, 147 (2011). R. Ganatra and Q. Zhang, ACS Nano, 8, 4074 (2014). A. Nourbakhsh, A. Zubair, R. N. Sajjad, A. Tavakkoli K. G., W. Chen, S. Fang, X. Ling, J. Kong, M. S. Dresselhaus, E. Kaxiras, K. K. Berggren, D. Antoniadis, and T. Palacios, Nano Lett., 16 7798 (2016). A. Nourbakhsh, A. Zubair, S. Joglekar, M. Dresselhaus, and T. Palacios, Nanoscale, 18, 6122 (2017). D. Sarkar, X. Xie, W. Liu, W. Cao, J. Kang, Y. Gong, S. Kraemer, P. M. Ajayan and K. Banerjee, Nature, 526, 91 (2015).

Here, we report the photoconducting response of field-effect transistors based on three atomic layers of chemical vapor transport grown WSe2 crystals mechanically exfoliated onto SiO2. We find that trilayered WSe2 field-effect transistors, built with the simplest possible architecture, can display high hole mobilities ranging from 350 cm(2)/(V s) at room temperature (saturating at a value of ∼500 cm(2)/(V s) below 50 K) displaying a strong photocurrent response, which leads to exceptionally high photoresponsivities up to 7 A/W under white light illumination of the entire channel for power densities p10(2) W/m(2). Under a fixed wavelength of λ = 532 nm and a laser spot size smaller than the conducting channel area, we extract photoresponsitivities approaching 100 mA/W with concomitantly high external quantum efficiencies up to ∼40% at room temperature. These values surpass values recently reported from more complex architectures, such as graphene and transition metal dichalcogenides based heterostructures. Also, trilayered WSe2 phototransistors display photoresponse times on the order of 10 μs. Our results indicate that the addition of a few atomic layers considerably decreases the photoresponse times, probably by minimizing the interaction with the substrates, while maintaining a very high photoresponsivity.

We have measured circularly polarization resolved photoluminescence in monolayer MoSe2 under magnetic fields up to 10 T in the Faraday geometry. The circularly polarized photoluminescence correspond to the emission from the K and K′ valleys, respectively. At low doping densities, the neutral and charged excitons shift linearly with field strength at a rate of \( \mp 0.12\;\mathrm{meV}/\mathrm{T} \) for emission arising from the two valleys, respectively. The opposite sign for emission from different valleys demonstrates lifting of the valley degeneracy. The magnitude of the Zeeman shift agrees with predicted magnetic moments for carriers in the conduction and valence bands. The relative intensity of neutral and charged exciton emission is modified by the magnetic field, reflecting the creation of field-induced valley polarization. At high doping levels, the Zeeman shift of the charged exciton increases to \( \mp 0.18\;\mathrm{meV}/\mathrm{T} \). This enhancement is attributed to many-body effects on the binding energy of the charged excitons [1].

Transition metal dichalcogenides (TMDs) are layered semiconductors with indirect band gaps comparable to Si. These compounds can be grown in large area, while their gap(s) can be tuned by changing their chemical composition or by applying a gate voltage. The experimental evidence collected so far, points towards a strong interaction with light, which contrasts with the small photovoltaic efficiencies $\eta \geq 1$ % extracted from bulk crystals or exfoliated monolayers. Here, we evaluate the potential of these compounds by studying the photovoltaic response of electrostatically generated PN-junctions composed of approximately ten atomic-layers of MoSe$_2$ stacked onto the dielectric $h$-BN. In addition to ideal diode-like response, we find that these junctions can yield, under AM-1.5 illumination, photovoltaic efficiencies $\eta$ exceeding 14 %, with fill-factors of ~ 70 %. Given the available strategies for increasing $\eta$ such as gap tuning, improving the quality of the electrical contacts, or the fabrication of tandem cells, our study suggests a remarkable potential for photovoltaic applications based on TMDs., Comment: Over 25 pages with the inclusion of the supplementary information (Nano Letters, in press)

Purpose To compare and analyze biomechanical properties and histological characteristics of flexor tendons either repaired by a 4-strand modified Kessler technique or using barbed suture with a knotless repair technique in an in vivo model. Methods A total of 25 chickens underwent surgical transection of the flexor digitorum profundus tendon followed by either a 4-strand Kessler repair or a knotless repair with barbed suture. Chickens were randomly assigned to 1 of 3 groups with various postoperative times to death. Harvested tendons were subjected to biomechanical testing or histologic analysis. Results Harvested tendons revealed failures in 25% of knotless repairs (8 of 32) and 8% of 4-strand Kessler repairs (2 of 24). Biomechanical testing revealed no significant difference in tensile strength between 4-strand Kessler and barbed repairs; however, this lack of difference may be attributed to lower statistical power. We noted a trend toward a gradual decrease in strength over time for barbed repairs, whereas we noticed the opposite for the 4-strand Kessler repairs. Mode of failure during testing differed between repair types. The barbed repairs tended toward suture breakage as opposed to 4-strand Kessler repairs, which demonstrated suture pullout. Histological analysis identified no difference in the degree of inflammation or fibrosis; however, there was a vigorous foreign body reaction around the 4-strand Kessler repair and no such response around the barbed repairs. Conclusions In this model, knotless barbed repairs trended toward higher in vivo failure rates and biomechanical inferiority under physiologic conditions, with each repair technique differing in mode of failure and respective histologic reaction. We are unable to recommend the use of knotless barbed repair over the 4-strand modified Kessler technique. Clinical relevance For the repair techniques tested, surgeons should prefer standard Kessler repairs over the described knotless technique with barbed suture.

Magnetophotoluminescence and magnetotransport were studied in a GaAs/AlGaAs triple quantum well. Oscillations of the photoluminescence intensity observed in tilted magnetic fields were found to correspond to the interlayer tunneling quantum Hall gap collapses detected in magnetoresistance measurements and predicted to occur in tilted magnetic fields. The obtained experimental data were shown to agree well with the theory developed for double quantum wells. This implies that the observed quantum Hall gap collapses are mostly caused by the tunneling between a pair of quantum wells. Our results reveal spectroscopic evidence of the quantum Hall gap collapses. Indications of interlayer correlation effects influencing a character of the inter-Landau-level gaps were found.

We report on Landau level spectroscopy studies of two HgTe quantum wells (QWs) near or at the critical well thickness, where the band gap vanishes. In magnetic fields up to $B$=16T, oriented perpendicular to the QW plane, we observe a $\sqrt{B}$ dependence for the energy of the dominant cyclotron resonance (CR) transition characteristic of two-dimensional Dirac fermions. The dominant CR line exhibits either a single or double absorption lineshape for the gapless or gapped QW. Using an effective Dirac model, we deduce the band velocity of single valley Dirac fermions in gapless HgTe quantum wells, $v_F=6.4 \times10^5$ m/s, and interpret the double absorption of the gapped QW as resulting from the addition of a small relativistic mass.

Linearly polarized photoluminescence is observed for type-II ZnTe/ZnSe submonolayer quantum dots (QDs). The comparison of spectral dependence of the degree of linear polarization (DLP) among four samples indicates that the optical anisotropy is mostly related to the elongation of ZnTe QDs. Numerical calculations based on the occupation probabilities of holes in px and py orbitals are performed to estimate the lateral aspect ratio of the QDs, and it is shown that it varies between 1.1 and 1.4. The value of anisotropic exchange splitting for bright excitonic states is found to be ∼200 μeV from the measurement of the degree of circular polarization as a function of the magnetic field. The results also show that heavy-light hole mixing ratio is about 0.16.

The electronic properties of unstrained unrelaxed InAs x Sb1−x alloys have been determined in a wide range of alloy compositions using IR magnetospectroscopy, magnetotransport and IR photoluminescence. All studied alloys have n-type background doping with electron concentration decreasing with the Sb content. The composition dependence of the background doping concentration follows an empirical exponential law in a wide range of compositions. Both bandgap and electron effective mass dependence on alloy composition exhibit negative bowing reaching lowest values at x = 0.63: E g = 0.10 eV, m* = 0.0082 m 0 at 4.2 K. The bowing coefficient of 0.038 m 0 obtained for the electron effective mass is in good agreement with that obtained from the Kane model.

For submonolayer quantum dot (QD) based photonic devices, size and density of QDs are critical parameters, the probing of which requires indirect methods. We report the determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer QDs, based on spectral analysis of the optical signature of Aharanov-Bohm (AB) excitons, complemented by photoluminescence studies, secondary-ion mass spectroscopy, and numerical calculations. Numerical calculations are employed to determine the AB transition magnetic field as a function of the type-II QD radius. The study of four samples grown with different tellurium fluxes shows that the lateral size of QDs increases by just 50%, even though tellurium concentration increases 25-fold. Detailed spectral analysis of the emission of the AB exciton shows that the QD radii take on only certain values due to vertical correlation and the stacked nature of the QDs.