Semiconductor Heterostructures Research Articles

Extreme electron-hole drag and negative mobility in the Dirac plasma of graphene.

Coulomb drag between adjacent electron and hole gases has attracted considerable attention, being studied in various two-dimensional systems, including semiconductor and graphene heterostructures. Here we report measurements of electron-hole drag in the Planckian plasma that develops in monolayer graphene in the vicinity of its Dirac point above liquid-nitrogen temperatures. The frequent electron-hole scattering forces minority carriers to move against the applied electric field due to the drag induced by majority carriers. This unidirectional transport of electrons and holes results in nominally negative mobility for the minority carriers. The electron-hole drag is found to be strongest near room temperature, despite being notably affected by phonon scattering. Our findings provide better understanding of the transport properties of charge-neutral graphene, reveal limits on its hydrodynamic description, and also offer insight into quantum-critical systems in general.

Nanoindentation of nano-SiC/Si hybrid crystals and AlN, AlGaN, GaN, Ga<sup>2</sup>O<sup>3</sup> thin films on nano-SiC/Si

The review presents systematization and analysis of experimental data on nanoindentation (NI) of a whole class of new materials – wide-gap AlN, GaN, AlGaN and β-Ga2O3 heterostructures formed on a hybrid substrate of a new SiC/Si type, which were synthesized by the method of coordinated atom substitution. The deformational and mechanical properties of the investigated materials are described in detail. The methodology of the NI is described, and both advantages and disadvantages of the NI method were analyzed. The description of the apparatus to conduct the experiments on NI was given. The basic provisions of a new model for describing the deformation properties of a nanoscale rigid two-layer structure on a porous elastic base were proposed. The original method of visualization of residual (after mechanical interaction) deformation in transparent and translucent materials was described. Experimentally determined values of elastic moduli and hardness of SiC nanoscale layers on Si formed by the method of coordinated substitution on three main crystal planes of Si, namely (100), (110) and (111), and elastic moduli and characteristics (elastic modulus, hardness, strength) of surface layers of semiconductor heterostructures AlN/SiC/Si, AlGaN/SiC/Si, AlGaN/AlN/SiC/Si, GaN/SiC/Si and GaN/AlN/SiC/Si grown on SiC/Si hybrid substrates. The unique mechanical properties of a new material β-Ga2O3 formed on SiC layers grown on Si surfaces of orientations (100), (110) and (111) were described.

Highly Active MXene Quantum Dots/CuSe n-p Plasmonic Heterostructures for Ultrafast Photocatalytic Removal of Cr(VI) under Full Solar Spectrum.

Identifying effective plasmonic photocatalysts exhibiting robust activities across the entire solar spectrum poses a significant challenge. CuSe, with its local surface plasmon resonance (LSPR) effect, has garnered attention as a prospective plasmonic photocatalyst. However, severe charge recombination and insufficient light absorption limit its photocatalytic performance. To enhance the performance, constructing CuSe-based n-p plasmonic semiconductor heterostructures is a potential strategy. MXene quantum dots (MQDs), a kind of n-type plasmonic semiconductor with metallic conductivity and a high LSPR effect, are a promising candidate to couple with p-type CuSe. According to the complementary principle, we designed a 0D/2D MQDs/CuSe n-p plasmonic semiconductor, achieved by wrapping CuSe nanosheets with MQDs. This n-p plasmonic heterostructure exhibits a synergistic effect on an enhanced electronic field, facilitating charge transfer and separation, thereby enhancing charge excitation, carrier migration, and photothermal effect. Furthermore, optimizing the MQD loading content leads to an ultrafast photocatalytic reaction rate, achieving 100% Cr(VI) reduction efficiency within just 60 min with a reaction kinetics of 0.069 min-1, surpassing the performance of bare CuSe. Our work presents a promising approach for developing advanced n-p plasmonic heterostructures based on MQDs for wastewater treatment and other photocatalytic applications.

Parity-independent Kondo effect of correlated electrons in electrostatically defined ZnO quantum dots

Quantum devices such as spin qubits have been extensively investigated in electrostatically confined quantum dots using high-quality semiconductor heterostructures like GaAs and Si. Here, we present a demonstration of electrostatically forming the quantum dots in ZnO heterostructures. Through the transport measurement, we uncover the distinctive signature of the Kondo effect independent of the even-odd electron number parity, which contrasts with the typical behavior of the Kondo effect in GaAs. By analyzing temperature and magnetic field dependences, we find that the absence of the even-odd parity in the Kondo effect is not straightforwardly interpreted by the considerations developed for conventional semiconductors. We propose that, based on the unique parameters of ZnO, electron correlation likely plays a fundamental role in this observation. Our study not only clarifies the physics of correlated electrons in the quantum dot but also holds promise for applications in quantum devices, leveraging the unique features of ZnO.

Controlled growth of two-dimensional MoS2/WSe2 heterostructure solar cell by chemical vapor deposition

The development of high-quality type II semiconductor heterostructures is crucial for solar energy conversion applications. Here, we report the sequential growth of MoS2/WSe2 two-dimensional semiconductor type II heterostructure using a one-step chemical vapor deposition. The morphological, Raman, and chemical analysis revealed that the WSe2 layer is deposited on the rhombus-shaped MoS2, forming a vertical MoS2/WSe2 heterostructure. The solar cell fabricated using the grown heterostructure exhibits a photovoltaic response with a conversion efficiency of 2.5 % and an open circuit voltage of 0.22 V, respectively. The numerical simulation study unravels the mechanism of charge separation and transport in the MoS2/WSe2 heterostructure solar cell.

Enhanced photocatalytic hydrogen and oxygen evolution activity by two-dimensional van der Waals AlSb/ZnO heterostructure: A first-principles study

Photocatalytic water splitting facilitates the generation of green hydrogen energy by transforming renewable solar energy into chemical energy. This paper investigated the electronic, optical, and photocatalytic properties of AlSb/ZnO van der Waals (vDW) heterostructure using density functional theory. AlSb/ZnO, a semiconductor heterostructure with an indirect bandgap, was energetically stable with a formation energy of −0.4 eV as well as dynamically and thermally stable. The band edges of the 2D heterostructure maintained the essential redox energy levels for complete water splitting, allowing hydrogen and oxygen generation. Moreover, the heterostructure exhibited a high absorption coefficient in the visible region of the solar spectrum compared to the individual AlSb and ZnO monolayers. We revealed low barrier potential at neutral pH conditions for oxygen and hydrogen evolution reactions from the Gibbs free energy calculation without any external potential. Our study additionally showed the solar-to-hydrogen efficiency of 27.93% and a carrier utilization efficiency of 42.83%, indicating the AlSb/ZnO heterostructure as an excellent water splitting photocatalyst with remarkable potential for fuel cells and energy storage applications.

Intracellular Gold Nanocluster/Organic Semiconductor Heterostructure for Enhancing Photosynthesis

AbstractPhotosynthetic microorganisms, which rely on light‐driven electron transfer, store solar energy in self‐energy carriers and convert it into bioenergy. Although these microorganisms can operate light‐induced charge separation with nearly 100 % quantum efficiency, their practical applications are inherently limited by the photosynthetic energy conversion efficiency. Artificial semiconductors can induce an electronic response to photoexcitation, providing additional excited electrons for natural photosynthesis to improve solar conversion efficiency. However, challenges remain in importing exogenous electrons across cell membranes. In this work, we have developed an engineered gold nanocluster/organic semiconductor heterostructure (AuNCs@OFTF) to couple the intracellular electron transport chain of living cyanobacteria. AuNCs@OFTF exhibits a prolonged excited state lifetime and effective charge separation. The internalized AuNCs@OFTF permits its photogenerated electrons to participate in the downstream of photosystem II and construct an oriented electronic highway, which enables a five‐fold increase in photocurrent in living cyanobacteria. Moreover, the binding events of AuNCs@OFTF established an abiotic‐biotic electronic interface at the thylakoid membrane to enhance electron flux and finally furnished nicotinamide adenine dinucleotide phosphate. Thus, AuNCs@OFTF can be exploited to spatiotemporally manipulate and enhance the solar conversion of living cyanobacteria in cells, providing an extended nanotechnology for re‐engineering photosynthetic pathways.

The coupling effect of polarization and lattice strain on charge transfer between quintuple-layer Al2X3/Al2Y3 (X, Y = O, S, Se, Te; X ≠ Y) interfaces

The electronic properties of two-dimensional (2D) polar semiconductor heterostructures are closely related to the degree of interlayer charge transfer. Taking 2D quintuple-layer (QL)-Al2S3 and QL-Al2O3 semiconductor as examples, we study the electronic properties and interlayer charge transfer of QL-Al2S3/Al2O3 interfaces by first-principles calculations. The driving force of the directional interlayer charge transfer is the polarization electric field. The kinetic process of interface charge transfer is related to the charge (strain) distribution of QL-Al2S3 and QL-Al2O3. By changing the strain distribution of QL-Al2S3/Al2O3 interfaces with same polarization arrangement, the electronic properties and interfacial charge transfer of heterojunctions can be adjusted. Our work is an important indicator for understanding the dynamic process of interlayer charge transfer between 2D polar semiconductors. In addition, we propose one method for regulating the electronic properties of heterojunctions by coupling polarization and lattice strain.

Controllable Synthesis of WSe2-WS2 Lateral Heterostructures via Atomic Substitution.

The atomic substitution in two-dimensional (2D) materials is propitious to achieving compositionally engineered semiconductor heterostructures. However, elucidating the mechanism and developing methods to synthesize 2D heterostructures with atomic-scale precision are crucial. Here, we demonstrate the synthesis of monolayer WSe2-WS2 heterostructures with a relatively sharp interface from monolayer WSe2 using a chalcogen atom-exchange synthesis route at high temperatures for short periods. The substitution was initiated at the edges of monolayer WSe2 and the lateral diffuse along the heterointerface, and the reaction can be controlled by the precise reaction time and temperature. The lateral heterostructure and substitution process are studied by Raman and photoluminescence (PL) spectroscopies, electron microscopy, and device characterization, revealing a possible mechanism of strain-induced transformation. Our findings demonstrate a highly controllable synthesis of 2D layered materials through atom substitutional chemistry and provide a simple route to control the atomic structure.

Bottom-Up Formation of III-Nitride Nanowires: Past, Present, and Future for Photonic Devices.

The realization of semiconductor heterostructures marks a significant advancement beyond silicon technology, driving progress in high-performance optoelectronics and photonics, including high-brightness light emitters, optical communication,and quantum technologies. In less than a decade since 1997, nanowires research has expanded into new application-driven areas,highlighting a significant shift toward more challenging and exploratory research avenues. It is therefore essential to reflecton the past motivations for nanowires development, and explorethe new opportunities it can enable. The advancement of heterogeneous integration using dissimilar substrates, materials, and nanowires-semiconductor/electrolyte operating platforms is ushering in new research frontiers, including the development of perovskite-embedded solar cells, photoelectrochemical (PEC) analog and digital photonic systems, such as PEC-basedphotodetectors and logic circuits, as well as quantum elements, such assingle-photon emitters and detectors. This review offersrejuvenating perspectives on the progress of these group-III nitride nanowires,aiming to highlight the continuity of research toward high impact, use-inspired researchdirections in photonics and optoelectronics.

A Backgate for Enhanced Tunability of Holes in Planar Germanium.

Planar semiconductor heterostructures offer versatile device designs and are promising candidates for scalable quantum computing. Notably, heterostructures based on strained germanium have been extensively studied in recent years, with an emphasis on their strong and tunable spin-orbit interaction, low effective mass, and high hole mobility. However, planar systems are still limited by the fact that the shape of the confinement potential is directly related to the density. In this work, we present the successful implementation of a backgate for a planar germanium heterostructure. The backgate, in combination with a topgate, enables independent control over the density and the electric field, which determines important state properties such as the effective mass, the g-factor, and the quantum lifetime. This unparalleled degree of control paves the way toward engineering qubit properties and facilitates the targeted tuning of bilayer quantum wells, which promise denser qubit packing.

Universality of quantum phase transitions in the integer and fractional quantum Hall regimes

Fractional quantum Hall (FQH) phases emerge due to strong electronic interactions and are characterized by anyonic quasiparticles, each distinguished by unique topological parameters, fractional charge, and statistics. In contrast, the integer quantum Hall (IQH) effects can be understood from the band topology of non-interacting electrons. We report a surprising super-universality of the critical behavior across all FQH and IQH transitions. Contrary to the anticipated state-dependent critical exponents, our findings reveal the same critical scaling exponent κ = 0.41 ± 0.02 and localization length exponent γ = 2.4 ± 0.2 for fractional and integer quantum Hall transitions. From these, we extract the value of the dynamical exponent z ≈ 1. We have achieved this in ultra-high mobility trilayer graphene devices with a metallic screening layer close to the conduction channels. The observation of these global critical exponents across various quantum Hall phase transitions was masked in previous studies by significant sample-to-sample variation in the measured values of κ in conventional semiconductor heterostructures, where long-range correlated disorder dominates. We show that the robust scaling exponents are valid in the limit of short-range disorder correlations.

Pyroelectric field drived photocatalysis by ZnFe2O4/NaNbO3 heterojunction for dye degradation through integration of solar and thermal energy

A novel composite of ZnFe2O4/NaNbO3 (ZFO/NNO) nanorods with a p-n heterojunction structure was successfully synthesized via the hydrothermal method. The NNO nanorods were heated in situ using the photothermal effect of ZFO and subsequently cooled to room temperature, creating a cyclic heating and cooling process for ZFO/NNO. The catalytic activity of the resulting nanorods was assessed through the degradation of Rhodamine B, reaching 98% degradation efficiency after 180 min, attributed to the synergistic effect of pyrocatalysis and photocatalysis. Compared with NNO and ZFO individually, the enhanced performance of ZFO/NNO can be attributed to several synergistic factors, including the expanded spectral range of light absorption for ZFO, the establishment of the built-in electric field of the p-n junction between ZFO and NNO, and the NNO pyroelectric effect that further improved the charge transfer efficiency. Superoxide radicals and holes generated from photo-induced electrons were identified as the active species. Hydroxyl radicals generated from pyroelectrically-induced charge also participated in catalytic reaction. The combined effect of pyroelectric and photocatalytic processes could significantly improve the coupled pyro-photocatalytic reaction for pyroelectric semiconductor heterostructure, enabling the utilization of multiple energy sources, including solar and thermal energy.

Thermo-phototronic Effect in Double Semiconductor Heterostructures for Highly Sensitive Self-Powered Sensors

Thermo-phototronic Effect in Double Semiconductor Heterostructures for Highly Sensitive Self-Powered Sensors

Constructing of n‐Type Semiconductor Heterostructures for Efficient Hydrazine‐Assisted Hydrogen Production

AbstractHydrazine‐assisted water electrolysis presents a promising approach toward energy‐efficient hydrogen production. However, the progress of this technology is hindered by the limited availability of affordable, efficient, and durable catalysts. In this study, a feasible strategy is proposed for interface modulation that enables efficient hydrogen evolution and hydrazine oxidation through the construction of n‐type semiconductor heterostructures. The metal–semiconductor contacts are rationally designed using ruthenium nanoclusters and a range of metal oxide (M–O) semiconductor heterostructures, including p‐type semiconductor substrates (NiO, Co3O4, NiCo2O4, CuCo2O4, ZnCo2O4) and n‐type semiconductor substrate (Fe2O3). Intriguingly, Ru nanoclusters supported on p‐type M–O substrates induce a transition from p‐type M–O to n‐type M‐O/Ru. The design of n‐type semiconductor heterostructures can significantly reduce space‐charge regions and increase charge carrier concentration, thereby improving the electrical conductivity of electrocatalysts. Moreover, Ru atoms can serve as highly efficient active sites for hydrogen evolution reaction and hydrazine oxidation reaction. The NiO/Ru heterostructure can drive current densities of 10 and 100 mA cm−2 with only 0.021 and 0.22 V cell voltages for hydrazine‐assisted water electrolysis. This work provides new insights for the development of highly efficient semiconductor catalysts, enabling energy‐saving hydrogen production.

Investigations on Cylindrical Surrounding Double-Gate (CSDG) MOSFET using AlxGa1-xAs/InP: Pt with La2O3 oxide layer for fabrication.

The Cylindrical Surrounding Double-Gate MOSFET has been designed using Aluminium Gallium Arsenide in its arbitrary alloy form alongside Indium Phosphide with Lanthanum Dioxide as a high-ƙ dielectric material. The heterostructure based on the AlxGa1-xAs/InP: Pt has been used in the design and implementation of the MOSFET for RF applications. Platinum serves as the gate material, which has higher electronic immunity toward the Short Channel Effect and highlights semiconductor properties. The charge buildup is the main concern in the field of MOSFET design when two different materials are considered for fabrication. The usage of 2 Dimensional Electron Gas has been outstanding in recent years to help the electron buildup and charge carrier accumulation in the MOSFETs regime. Device simulation used for the smart integral systems is an electronic simulator that uses the physical robustness and the mathematical modeling of semiconductor heterostructures. In this research work, the fabrication method of Cylindrical Surrounding Double Gate MOSFET has been discussed and realized. The scaling down of the devices is essential to reduce the area of the chip and heat generation. By using these cylindrical structures, the area of contact with the circuit platform is reduced since the cylinder can be laid down horizontally. The coulomb scattering rate is observed to be 18.3 % lower than the drain terminal when compared to the source terminal. Also, at x = 0.125 nm, the rate is 23.9 %, which makes it the lowest along the length of the channel; at x = 1 nm, the rate is 1.4 % lesser than that of the drain terminal. A 1.4 A/mm2 high current density had been achieved in the channel of the device, which is significantly larger than comparable transistors. The conventional transistor occupies a larger area than the proposed cylindrical structures transistor and is also efficient in RF applications.

Semiconductor heterostructure LiCo0.5Al0.5O2-Ce0.8Sm0.2O2-δ electrolyte with enhanced ionic conductivity for low-temperature solid oxide fuel cells

Semiconductor heterostructure composite materials, exemplified by p-n junctions, have garnered substantial interest for their elevated ionic conductivity, crucial in solid oxide fuel cells (SOFCs). The inherent built-in electric field (BIEF) within these materials enhances ion transport while hindering electron flow, thereby mitigating the risk of short circuits. This research focuses on the electronic conduction properties of p-n junctions, specifically through the development of high-performance LiCo0.5Al0.5O2 (LCAO)-Ce0.8Sm0.2O2-δ (SDC) semiconductor heterojunction composite electrolytes for low-temperature solid oxide fuel cells (LT-SOFCs). Experimental results demonstrate a correlation between the electrolyte's performance and the LCAO to SDC weight ratio. The SOFC equipped with a 3LCAO-7SDC electrolyte achieved an open-circuit voltage (OCV) of 1.1 V and a maximum power density (MPD) of 1013 mW/cm2 at 550 °C, significantly outperforming other composite ratios and single-phase SDC electrolytes, which only reached 453 mW/cm2 under identical conditions. High-resolution transmission electron microscopy (HRTEM) revealed the presence of non-uniform interfaces within these composites. Energy band structure analyses confirm superior ionic conductivity and effective charge separation capabilities. This study introduces a novel p-n junction design for LT-SOFC electrolyte materials using LCAO-SDC, further advancing the exploration of p-n junctions in this application.

Designing Bi2O3-Sn3O4 Z-scheme heterojunction on TiO2 NTs for improving photocatalytic performance

The design of semiconductor heterostructures as the effective strategy are recognized to enhance the photocatalytic capacity of photocatalysts for the settlement of energy shortage and pollutant treatment. To efficiently utilize solar energy, the Bi2O3-Sn3O4 nanoparticles with the Z-scheme energy band structure were synthesized on TiO2 nanotube arrays (TiO2 NTs) by the solvothermal deposition method. The TiO2 NTs/Bi2O3-Sn3O4 exhibited the outstanding photocatalytic dye degradation and Cr(VI) removal, which was much higher than those of single Bi2O3 or Sn3O4 sensitized samples. The H2 evolution test indicated that the Bi2O3-Sn3O4 cosensitization dramatically enhanced the photocatalytic H2 generation ability of TiO2 NTs with the rate of 58.75 μmol·h−1·cm−2. The high photoelectric conversion was also confirmed, and the outstanding photocatalytic performance was further revealed by the contrast experiment. The plausible photocatalytic mechanism based on the ESR and capturing experiments indicated that the Z-scheme energy band structure induced the photoelectron separation and the generation of O2 and OH radicals, which was the decisive role for the improved photocatalytic performance.

An Active-Matrix Synaptic Phototransistor Array for In-Sensor Spectral Processing.

The human retina perceives and preprocesses the spectral information of incident light, enabling fast image recognition and efficient chromatic adaptation. In comparison, it is reluctant to implement parallel spectral preprocessing and temporal information fusion in current complementary metal-oxide-semiconductor (CMOS) image sensors, requiring intricate circuitry, frequent data transmission, and color filters. Herein, an active-matrix synaptic phototransistor array (AMSPA) is developed based on organic/inorganic semiconductor heterostructures. The AMSPA provides wavelength-dependent, bidirectional photoresponses, enabling dynamic imaging and in-sensor spectral preprocessing functions. Specifically, near-infrared light induces inhibitory photoresponse while UV light results in exhibitory photoresponse. With rational structural design of the organic/inorganic hybrid heterostructures, the current dynamic range of phototransistor is improved to over 90 dB. Finally, a 32 × 64 AMSPA (128 pixels per inch) is demonstrated with one-switch-transistor and one-synaptic phototransistor (1-T-1-PT) structure, achieving spatial chromatic enhancement and temporal trajectory imaging. These results reveal the feasibility of AMSPA for constructing artificial vision systems.

All-2D CVD-grown semiconductor field-effect transistors with van der Waals graphene contacts

Two-dimensional (2D) semiconductors and van der Waals (vdW) heterostructures with graphene have generated enormous interest for future electronic, optoelectronic, and energy-harvesting applications. The electronic transport properties and correlations of such hybrid devices strongly depend on the quality of the materials via chemical vapor deposition (CVD) process, their interfaces and contact properties. However, detailed electronic transport and correlation properties of the 2D semiconductor field-effect transistor (FET) with vdW graphene contacts for understanding mobility limiting factors and metal-insulator transition properties are not explored. Here, we investigate electronic transport in scalable all-2D CVD-grown molybdenum disulfide (MoS2) FET with graphene contacts. The Fermi level of graphene can be readily tuned by a gate voltage to enable a nearly perfect band alignment and, hence, a reduced and tunable Schottky barrier at the contact with good field-effect channel mobility. Detailed temperature-dependent transport measurements show dominant phonon/impurity scattering as a mobility limiting mechanisms and a gate-and bias-induced metal-insulator transition in different temperature ranges, which is explained in light of the variable-range hopping transport. These studies in such scalable all-2D semiconductor heterostructure FETs will be useful for future electronic and optoelectronic devices for a broad range of applications.