High Carrier Mobility Research Articles

A Review of Diamond Materials and Applications in Power Semiconductor Devices.

Diamond is known as the ultimate semiconductor material for electric devices with excellent properties such as an ultra-wide bandgap (5.47 eV), high carrier mobility (electron mobility 4000 cm2/V·s, hole mobility 3800 cm2/V·s), high critical breakdown electric field (20 MV/cm), and high thermal conductivity (22 W/cm·K), showing good prospects in high-power applications. The lack of n-type diamonds limits the development of bipolar devices; most of the research focuses on p-type Schottky barrier diodes (SBDs) and unipolar field-effect transistors (FETs) based on terminal technology. In recent years, breakthroughs have been made through the introduction of new structures, dielectric materials, heterogeneous epitaxy, etc. Currently, diamond devices have shown promising applications in high-power applications, with a BV of 10 kV, a BFOM of 874.6 MW/cm2, and a current density of 60 kA/cm2 already realized. This review summarizes the research progress of diamond materials, devices, and specific applications, with a particular focus on the development of SBDs and FETs and their use in high-power applications, aiming to provide researchers with the relevant intuitive parametric comparisons. Finally, the paper provides an outlook on the parameters and development directions of diamond power devices.

High-Performance WS2 MOSFETs with Bilayer WS2 Contacts.

WS2 is a promising transition-metal dichalcogenide (TMDC) for use as a channel material in extreme-scaled metal-oxide-semiconductor field-effect transistors (MOSFETs) due to its monolayer thickness, high carrier mobility, and its potential for symmetric n-type and p-type MOSFET performance. However, the formation of stable, low-barrier-height contacts to monolayer TMDCs continues to be a challenge. This study introduces an innovative approach to realize high-performance WS2 MOSFETs by utilizing bilayer WS2 (2L-WS2) in the contact region grown through a two-step chemical vapor deposition process. The 2L-WS2 devices demonstrate a high I ON/I OFF ratio of 108 and a saturated drain current, I D(SAT), of 280 μA/μm (386 μA/μm) at room temperature (78 K), even while still using conventional metal (Pd or Ni) contacts. Devices featuring a 1L-WS2 channel and 2L-WS2 in the contact regions were also fabricated, and they exhibited performance comparable to that of 2L-WS2 devices. The devices also exhibit good stability with nearly identical performance after storage over a 13 month period. The study highlights the benefits of a hybrid channel thickness approach for TMDC transistors.

Thermoelectric Performance Enhancement in SnS Polycrystals Owing to Hole Doping Combined with Textured Microstructures.

Recently, the earth-abundant tin sulfide (SnS) has emerged as a promising thermoelectric material due to its phonon and electron structure similar to that of tin selenide (SnSe). However, compared with SnSe, limited progress has been achieved in the thermoelectric property enhancement of SnS. Textured SnS polycrystals with an enhanced thermoelectric performance have been developed in this work. The high carrier mobility benefited from the enhanced texture through the repressing strategy of spark plasma sintering, improving the electrical conductivity. In addition, Sn atom deficiencies in the texture sample led to an increased hole concentration, further boosting the electrical conductivity and power factor. The power factor exceeded 4.10 μW/cm·K2 at 423 K and 5.50 μW/cm·K2 at 850 K. The phonon scattering was strengthened by adjusting the multiscale microstructures including dislocations, defect clusters, etc., leading to an ultralow lattice thermal conductivity of 0.23 W/m·K at 850 K. A figure of merit zT > 1.3 at 850 K and an average zTave of 0.58 in the temperature range 373-850 K were achieved in the SnS polycrystal.

Structural, electronic and optical properties of anisotropic AlN/BP van der Waals heterostructures with high carrier mobility and remarkable optical absorption

The structural, electronic and optical properties of van der Waals heterostructures (vdWHs) of AlN/BP 2D layers have been investigated. Using density functional theory (DFT) calculations, six distinct vertical arrangements of insulating plates composed of aluminum nitride (AlN) and boron phosphide (BP) examined. All six AlN/BP-XX (XX = AA, BB, CC, DD, EE, FF) heterostructures exhibit direct bandgap behavior with type-I band alignment. These heterostructures exhibit remarkable optical absorption in the visible and near-infrared regions, and at room temperature, charge carriers exhibit relatively high mobility for holes in one direction and for electrons in the perpendicular direction.All these six AlN/BP vdWHs have high carrier mobility (of the order of 105cm2V-1s-1), which is comparable to materials with high carrier mobility such as graphene. The energy gap of the AlN and BP monolayers are 4.04 eV and 1.4 eV, respectively, by HSE06 approximation, and for AlN/BP heterostructures are about 1.428 eV to 1.550 eV for all cases. The CBO and VBO of the AlN/BP vdWHs heterostructures are 2.21157 eV and 0.2057 eV, respectively.

Janus SnXY monolayers (X= P, As, Sb; Y[dbnd]H, CH3): A new class of two-dimensional photocatalysts for water splitting

Following the successful synthesis of NaSnAs in 2021, in the present study, a series of two-dimensional SnXY monolayers with X = P, As, Sb, and Y = H, CH3 are theoretically predicted. First principle calculations are performed to investigate the structural, electronic, mechanical, and optical properties of these materials. The results predict desirable dynamical and thermal stabilities with high mechanical strength for considered systems. It is found that all SnXY monolayers are semiconductors with a direct band-gap lying in the visible region. The values of band-gap decrease as the size of the X atom increases which indicates the dominant contribution of the X atom in the band edge positions. Employing biaxial strain leads to narrowing the electronic band-gaps and suggests a strain-tuneable band-gap character in these structures. The results also highlight high carrier mobilities along the SnXY monolayers. By virtue of possessing suitably large band gaps, well-matched band offsets, robust optical absorption within the visible spectrum, high carrier mobility, and moderate exciton binding energies, these systems are poised as prospective candidates for applications in photocatalysis. Accordingly, we have also explored the photocatalytic activity of SnPH and SnAsH monolayers toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The calculated reaction free energy profiles demonstrate the exceptional performance of these systems in facilitating overall water splitting. This study provides a comprehensive vision of novel 2D SnXY monolayers and a new outlook for designing superior photocatalysts for water splitting.

Density-functional theory study of SnSe/GeSe heterostructure for gaseous sulfur hexafluoride decomposition products sensing

Partial discharge, local overheating and other factors will lead to the decomposition of superior dielectric gas sulfur hexafluoride (SF6) used in gas insulated substations (GIS). Detecting gaseous sulfur hexafluoride (SF6) decomposition products by gas sensors to diagnose early latent insulation failures is a potential approach to guarantee safety and reliability of gas insulated substations (GIS). However, the main difficulties in the detection of SF6 decomposition products lie in sensitivity, operating temperature and sulfur poisoning of the sensor. Metal oxide selenides (MOSs)-based gas sensors suffer from high working temperature, long recovery time, and sulfur poisoning. Two dimensional selenides-based chemiresistor-type gas sensors have been reported to detect certain gases at room temperature. Compared with pristine materials, heterostructures usually have narrower band gaps and higher carrier mobility which promise low power and sensitivity. In this work, a SnSe/GeSe van der Waals heterostructure model is constructed and optimized to investigate the gas sensing properties by density functional theory (DFT) calculations. Compared with the pristine SnSe and the pristine GeSe, the SnSe/GeSe heterostructure exhibits huge adsorption energy and comparatively large charge transfer to the SF6 decomposition gases. The band structure analysis, charge analysis, electron localization function (ELF), and density of states (DOS) analysis suggest that the excellent sensing properties are contributed to the synergistic effect between the SnSe and the GeSe layers: both the layers transfer charge and orbitally interact with gas molecules. Besides, physical adsorption of the SF6 decomposition gases on SnSe/GeSe heterostructure avoids sulfur poisoning of the material, promising the recoverability and repeatability of detection. This study provides theoretical bases for the repeatable detection of SF6 decomposition products by SnSe/GeSe heterostructures and its potential in the design of electronic nose.

Solar-driven water splitting: Theoretical insights into M2Te5 (M=Al, In) monolayer photocatalysts

Two-dimensional (2D) semiconducting optical absorbers for photocatalytic applications have gained significant attention due to their unique physicochemical properties. Using density functional theory simulations, this study explores the M2Te5 (M = Al, In) monolayer, highlighting its potential as a robust optical absorber semiconductor for overall water splitting. Detailed analysis of the structural and electronic characteristics of these materials offers crucial insights into their photocatalytic potential. The study reveals that M2Te5 has an optimal band gap, favorable band edge positions, and high charge carrier mobility and transfer efficiency, essential for effective photocatalytic water splitting. The material also shows sufficient driving forces for the photoexcited carriers, particularly in facilitating the hydrogen evolution reaction under acidic conditions. Additionally, these monolayers exhibit impressive mechanical, dynamical, and thermal stabilities, with notable corrosion-resistant properties of In2Te5 against photoinduced effects.

Narrow bandgap two-dimensional Nb2SiTe4 as broadband saturable absorber for optical switch

Nb2SiTe4 is a novel narrow-bandgap (∼0.39 eV) two-dimensional material with a high optical absorption coefficient, high carrier mobility, and outstanding air stability, which shows great application potential in broadband optical switches. In this study, high-quality layered Nb2SiTe4 nanosheets were efficiently fabricated by the mechanical exfoliation method, and the basic characterizations were carried out comprehensively. Nondegenerate pump-probe technology was implemented to systematically explore the photocarrier dynamics in the Nb2SiTe4 nanosheets, which exhibit the ultrafast recovery time of Nb2SiTe4 (∼0.3 ps). Furthermore, broadband passively Q-switched lasers operating at 1.0, 2.0, and 2.8 μm with the shortest pulse width of 380, 549, and 218 ns were achieved based on Nb2SiTe4 saturable absorber. This work demonstrates the significant advantages of an optical switch based on Nb2SiTe4 saturable absorber, including a narrow output pulse width, wide working bandwidth, high damage threshold, excellent oxidation resistance, and a straightforward synthesis method, which underscore the immense potential of Nb2SiTe4 broadband optical switches in applications involving mid-infrared lasers.

Exploration of lead-free novel double perovskite halides Na2TlBiX6 (X = Cl, Br, I) for flexible memory devices: Using DFT approach

Flexible resistive switching random access memory (RRAM) devices have drawn significant attention due to their low power consumption, high speed and simple structure. Halide perovskites with excellent optoelectronic properties such as high charge carrier mobility and tunable bandgap emerge as the best material for flexible RRAM devices. In this study, for the first time, the structural, mechanical, optoelectronic and thermoelectric properties of Na2TlBiX6 (X = Cl, Br, I) were explored using the Wien2k package for flexible RRAM devices. Elastic parameters show that studied perovskites display mechanical stability, ductile nature and anisotropic behaviour with lower values of the bulk modulus. In comparison, Na2TlBiI6 has a smaller bulk modulus which makes it a suitable material for flexible RRAM devices. Furthermore, the large machinability index of Na2TlBiI6 among the studied perovskites highlights its feasibility for industrial applications. The semiconductor nature of Na2TlBiX6 (X = Cl, Br, I) is confirmed from band structure, total density of states (TDOS) and partial density of states (PDOS) calculation. The optical study shows that Na2TlBiI6 can absorb a wide range of ultraviolet and visible electromagnetic incident radiations making it an excellent material for flexible RRAM devices. Lastly, in terms of transport properties at room temperature, Na2TlBiI6 reveals a larger figure of merit (ZT) than other studied perovskites making it a suitable candidate for thermoelectric applications. The outcome of this study suggests that Na2TlBiI6 is the perfect candidate for flexible RRAM devices at room temperature.

High pressure coupled with Cu deficiency boosts thermoelectric performance in BiCuSeO oxides

Low carrier concentration and mobility have been the primary obstructions to improving the electrical transport properties of BiCuSeO thermoelectric oxides, particularly for excessively low carrier mobility, heavily impeding the development of its thermoelectric performance. Herein, high-pressure technology is adopted to tune the electronic structure motivating carrier mobility, incorporated with the contribution of Cu deficiency to carrier concentration, achieving high carrier mobility of 25 cm2V−1s−1 and outstanding electrical conductivity of 2834.57 Sm−1. Moreover, high densities of grain boundaries and dislocations are introduced by high pressure, accompanied by the effect of Cu vacancies, suppressing phonon transport and depressing lattice thermal conductivity, finally realizing an acceptable zT of 0.56 at 823 K in BiCu0.97SeO. This work demonstrates that high pressure can be compatible with other methods, realizing synergetic optimizations in coupled parameters and thus improving thermoelectric performance in BiCuSeO oxides.

A comprehensive analysis of ultra low power GNRFET based 20T hybrid full adder for computing applications

In an era where energy efficiency is as important as computational speed, this paper introduces a new full adder circuit design that effectively integrates dynamic power gathering (DPG) power conservation benefits with XOR-XNOR pass-transistor logic (PTL) area and performance efficiencies using graphene nanoribbon field-effect transistors. GNRFETs are useful for digital logic due to their high carrier mobility and tunable bandgap. The paper describes the circuit’s seamless transition full adder response, demonstrating the tri-mode dynamic power gating strategy capacity to reduce static power depletion. The proposed hybrid full adder performs well with 7.76 nW power consumption, 481 ps latency, and 3.73 aJ PDP. This reduces power consumption by 99.9%, delay by 99.0%, and PDP by 99.8% compared to other adders. The effects of temperature, voltage, Noise immunity and Carry Forward Adders integration on power, delay, and PDP are also analysed, proving the design’s robustness. The adaptability of our full adder architecture allows its implementation in more complicated arithmetic and logic units, indicating a scalable and energy-efficient paradigm for future integrated circuits.

2D Janus TeMoZAZ’ (A = Si,Ge; Z,Z’ = N, P, As; Z ≠ Z'): First‐Principles Insight into the Electronics, and Piezoelectric Properties

AbstractJanus materials possess a diverse array of properties resulting from the breaking of mirror and inversion symmetries, holding significant potential for nanodevices. This study explores the novel TeMoZAZ' (A = Si,Ge; Z,Z' = N, P, As; Z ≠ Z') monolayers derived from the MoA2Z4 monolayer. Utilizing first‐principles calculations, the stability, electronic, transport, mechanical, and piezoelectric properties of the TeMoZAZ' monolayers are investigated. Among the 12 investigated structures, only five‐ TeMoNSiP, TeMoNSiAs, TeMoPSiAs, TeMoAsSiP and TeMoAsGeP monolayers‐ are found to be stable. The electronic properties analysis reveals metallic behavior in the TeMoNSiAs monolayer, while the remaining structures exhibit indirect or direct band gap semiconductor properties. Futher examination of the semiconducting monolayers indentifies the TeMoAsSiP monolayer with notably high hole carrier mobility along the y‐direction, reaching up to 3622.33 cm2 s−1 V−1. Moreover, investigation into the piezoelectric properties of these four semiconductor structures suggests their suitability for diverse applications in piezoelectric devices. Additionally, the effects of biaxial strain on the electronic and piezoelectric properties of these four semiconductor structures are explored. These findings propose a novel approach for designing 2D Janus materials, expanding the repertoire of 2D MA2Z4‐based Janus family and offering promising candidates for optoelectronic devices, wearable devices, and electromechanical systems.

Principles, fabrication, and applications of halide perovskites‐based memristors

AbstractIn recent decades, the microelectronics industry has developed rapidly based on the von Neumann architecture and under the guidance of Moore's law. However, as the size of electronic devices approaches the limit and power consumption increases, traditional microelectronic materials and devices are facing more and more challenges. As a new type of semiconductor material, halide perovskites (HPs) have excellent photoelectric characteristics, such as high carrier mobility, controllable band structure, etc., which have been widely used in solar cells, light emitting diodes (LEDs), photodetectors, memristors, and in other fields. Among them, the memristor, as a new type of electronic device, is very promising for in‐memory computing with low power consumption by breaking the limit of von Neumann architecture. Especially, HPs‐based memristors show outstanding photoelectric response performance, low power consumption, and flexible wearability, allowing them to hold great application potential in logical operation, polymorphic storage, and neuromorphic computing, etc. In this review, we first briefly introduce the basic characteristics and preparation methods of HPs. Secondly, the development history, device structure, and performance parameters of memristors are depicted in detail. Thirdly, the resistance mechanism and application of HPs‐based memristors are discussed. Finally, the research status and development prospects of HPs‐based memristors are outlined.

A density functional theory study on the photocatalytic performance of PtS2 nanotubes with high carrier mobility for photocatalytic water splitting

In this paper, the electronic and photocatalytic properties of PtS2 nanotubes have been further investigated by means of first-principles approach. We observed that the band gap of PtS2 nanotubes increases with the increase of the radius, while the strain energy decreases with the increase of the radius. Significantly, the electron mobility of PtS2 nanotubes was 1.34 × 103cm2V-1S-1, while the hole mobility was only 15.95 cm2V-1S-1. The band edge positions of PtS2 nanotubes at pH=0 can satisfy the requirement of the water splitting redox potential. Moreover, the band gap is decreased by strain regulation which should expand the light absorption range. Based on these important findings, we expect that PtS2 nanotubes will have great potential in photocatalytic material applications.

Epitaxial Growth of Monolayer SnP3 with High Mobility and Chiral Boundary Junctions.

Two-dimensional materials with layered structures, appropriate band gaps, and high carrier mobility have attracted tremendous interest for their potential applications. Here we report the growth of monolayer SnP3 on Au(111) surfaces by molecular beam epitaxy. The kinetic processes for the growth and the crystalline properties are studied by scanning tunneling microscopy. The weak interaction between SnP3 and its Au(111) substrate is signified by the random crystal orientation distributions of SnP3 nanosheets. The electronic structures exhibit a band gap of ∼0.25 eV and high charge carrier mobility comparable to that of black phosphorus engineered by compressive strain. Additionally, domain boundary junctions with opposite chirality are observed, resulting from the strained film in the epitaxial growth process. Our work provides a method to fabricate high-quality monolayer SnP3 and suggests that the monolayer SnP3 is a promising candidate for applications in nanoelectronics and optoelectronics.

Ice-Enabled Transfer of Graphene on Copper Substrates Enhanced by Electric Field and Cu2O.

Graphene films grown by the chemical vapor deposition (CVD) method suffer from contamination and damage during transfer. Herein, an innovative ice-enabled transfer method under an applied electric field and in the presence of Cu2O (or Cu2O-Electric-field Ice Transfer, abbreviated as CEIT) is developed. Ice serves as a pollution-free transfer medium while water molecules under the electric field fully wet the graphene surface for a bolstered adhesion force between the ice and graphene. Cu2O is used to reduce the adhesion force between graphene and copper. The combined methodology in CEIT ensures complete separation and clean transfer of graphene, resulting in successfully transferred graphene to various substrates, including polydimethylsiloxane (PDMS), Teflon, and C4F8 without pollution. The graphene obtained via CEIT is utilized to fabricate field-effect transistors with electrical performances comparable to that of intrinsic graphene characterized by small Dirac points and high carrier mobility. The carrier mobility of the transferred graphene reaches 9090 cm2V-1s-1, demonstrating a superior carrier mobility over that from other dry transfer methods. In a nutshell, the proposed clean and efficient transfer method holds great potential for future applications of graphene.

Efficient visible-light-driven photocatalytic hydrogen evolution in novel type-II SnS2/Al2S2 van der Waals heterostructures

With the exacerbation of environmental pollution and the energy crisis, the development and design of environmentally friendly and efficient photocatalytic catalysts for water splitting with visible light have become particularly imperative. This study delves into the detailed investigation of the novel type-II van der Waals heterostructure of SnS2/Al2S2 utilizing first-principles calculation methods. By leveraging the advantages of indirect type-II band alignment and high carrier mobility, the efficient separation of electron-hole pairs is achieved, thereby facilitating enhanced participation of electrons and holes in photocatalytic reactions. Furthermore, the heterostructure manifests a peak optical absorption coefficient value of approximately 5.34×104 cm−1 in the visible light spectrum, accompanied by the occurrence of red-shifting, which fosters efficient absorption of visible light. It is noteworthy that under conditions of pH = 0–3.7, the heterojunction surpasses the redox potential of water splitting, concurrently displaying a substantial hydrogen evolution reaction (HER) and a high efficiency of converting sunlight to hydrogen (22.31 %). These results underscore the promising potential of the SnS2/Al2S2 heterostructure as a photocatalyst for water splitting, offering crucial theoretical support and practical guidance for the further advancement of hydrogen production via water splitting technology.

A Revisit of Crystallization in Tin Halide Perovskite Thin Films: From Nucleation, Intermediate to Crystal Growth

AbstractPerovskite solar cells (PSCs) are exuding unique charm in the third generation of thin film solar cell technology with high power conversion efficiency (PCE) and low production cost. Recently, the lead‐free tin halide perovskite solar cells (TPSCs) have drawn significant research interests due to the advantages of low toxicity, near‐ideal bandgap and high carrier mobility. However, the rapid crystallization and easy oxidation limits the film quality and final performance of the solar cells. Therefore, the deposition of high‐quality tin halide perovskite films is key to the advance of TPSCs. In this review, the classical theory of solution nucleation and crystal growth is reviewed and correlated to the practical deposition of tin perovskite film. The physicochemical properties of tin perovskite with those of lead counterpart and the differences in the crystallization process is carefully compared. On this basis, recent regulation strategies are systematically summarized in terms of the nucleation management, intermediate phase engineering and crystal growth regulation. In addition, the preparation of mixed tin‐lead (Sn‐Pb) PSCs toward high performance is also discussed, as well as the limiting factors for device performance and stability. Finally, the future challenges and prospects of the crystallization regulation are discussed toward more efficient and stable TPSCs.

Perovskite nanowire-based electrochemical sensing for selective and rapid detection of hydrogen peroxide

Nanowires possess inherent advantages in improving the reduction of boundary stacking defects and enhancing charge transfer or migration. Here, we synthesized all-inorganic perovskite nanowires CsPbBr3 (PVSK NW) and obtained CsPb1-xSnxBr3 (PVSK-Sn NW) and CsPb1-xGexBr3 (PVSK-Ge NW) nanowires through doping with different elements (Sn and Ge). Elemental doping endows the nanowires with unique narrow fluorescence spectra, high optical absorption coefficients, tunable optical bandgaps, and high carrier mobility. Introducing different perovskite nanowires into carbon-based composite materials (super p/Nafion) can overcome the challenges of hydrogen peroxide (H2O2) detection sensitivity and matrix interference. H2O2 in PBS (phosphate buffered saline) solution (pH 7.0) was detected by current analysis i-t curve mode. The results demonstrate that the addition of perovskite nanowires exhibits a high level of detection sensitivity for H2O2 electrochemical reduction. Particularly, the linear concentration range detected by PVSK-Sn NW is 1–6000 µM, with a detection limit of 0.12 µM. Even in the presence of interfering molecules (ascorbic acid, uric acid, glucose), the detection of H2O2 maintains high sensitivity and selectivity. This study overcomes the limitations of perovskite materials in water-based detection, enhancing their future commercial applications as sensing devices.

Large-area solution-processable black phosphorus for electronic application

Two-dimensional (2D) layered black phosphorus (BP), with a direct band gap and high carrier mobility, has shown great potential for next generation electronics and optoelectronics. However, how to prepare a large-area 2D material film is still a big problem for realizing its practical applications. Herein, an improved one-step solution-processable method is put forward to solving this problem to get uniform and large-area BP film. Our results show that the designed electrodes can be fully covered by BP flakes and the corresponding FET reveals relatively high performance. Our study opens a new avenue in fabricating large-area ultra-thin BP films.