Low-dimensional Semiconductor Research Articles

The Modified Guyer-Krumhansl Equations Derived From the Linear Boltzmann Transport Equation

Abstract Phonon hydrodynamics originated from the macroscopic energy and momentum balance equations (called Guyer-Krumhansl equations) proposed by Guyer and Krumhansl by solving the linearized Boltzmann transport equation for studying second sound in the normal-process collision dominated phonon transports in an isotropic non-metallic crystal with a dispersionless frequency spectrum. However, the low-dimensional dielectric materials and semiconductors are anisotropic, and the different branches in their phonon frequency spectrums usually have different group velocities. For such materials we derive the macroscopic energy and momentum balance equations from the linear Boltzmann transport equation to describe the phonon hydrodynamic transport, and solve the long standing debate about whether the energy balance equation contains the second-order spatial derivatives of temperature.

The influence of light on transverse magnetoresistance oscillations in low-dimensional semiconductor structures

The influence of light on transverse magnetoresistance oscillations in low-dimensional semiconductor structures

Carbon-silicon based hybrid quantum dot short wave infrared photodetector

Recently infrared photodetectors based on low-dimensional semiconductors have developed rapidly. However, due to its poor light absorption and incompatibility with traditional silicon-based readout circuit processes, the sensitivity and integration of such photodetectors are limited. In this work, we proposes a 64 × 64 quantum dot short-wavelength infrared (SWIR) photodetector composed of carbon nanotube thin film transistor (CNT TFT) and silicon-based ROIC. CNT TFT's gate is constructed by PbS colloidal quantum dots (PbS CQDs) which improve the absorption rate of infrared light. The generated photovoltage is amplified and converted in situ by CNT TFT. Notably, under infrared radiation of 1300 nm, the noise equivalent current reach up to 1.25*10−13A/Hz1/2. At a drain-source bias (Vds)= -0.1 V. The device exhibits detectivity of 5.6*1013 Jones and a fast response of 0.57 ms. The silicon-based ROIC is implemented by CMOS 0.18um process, with a power supply voltage of 1.8 V. It mainly includes a programmable integrator, a sampling and holding circuit, and a 10bit/2.5 MHz successive approximation analog-to-digital converter (SAR ADC). The programmable integrator has four levels of integral gain to meet the application requirements of different infrared light intensities. The experiment results show that the imaging function of the overall photodetector is correct, laying the foundation for the development of carbon-silicon based heterojunction integrated photodetector in the future.

Ultrastrong exciton-plasmon couplings in WS2 multilayers synthesized with a random multi-singular metasurface at room temperature.

Van der Waals semiconductors exemplified by two-dimensional transition-metal dichalcogenides have promised next-generation atomically thin optoelectronics. Boosting their interaction with light is vital for practical applications, especially in the quantum regime where ultrastrong coupling is highly demanded but not yet realized. Here we report ultrastrong exciton-plasmon coupling at room temperature in tungsten disulfide (WS2) layers loaded with a random multi-singular plasmonic metasurface deposited on a flexible polymer substrate. Different from seeking perfect metals or high-quality resonators, we create a unique type of metasurface with a dense array of singularities that can support nanometre-sized plasmonic hotspots to which several WS2 excitons coherently interact. The associated normalized coupling strength is 0.12 for monolayer WS2 and can be up to 0.164 for quadrilayers, showcasing the ultrastrong exciton-plasmon coupling that is important for practical optoelectronic devices based on low-dimensional semiconductors.

Role of Pyramidal Low-Dimensional Semiconductors in Advancing the Field of Optoelectronics

Numerous optoelectronic devices based on low-dimensional nanostructures have been developed in recent years. Among these, pyramidal low-dimensional semiconductors (zero- and one-dimensional nanomaterials) have been favored in the field of optoelectronics. In this review, we discuss in detail the structures, preparation methods, band structures, electronic properties, and optoelectronic applications (photocatalysis, photoelectric detection, solar cells, light-emitting diodes, lasers, and optical quantum information processing) of pyramidal low-dimensional semiconductors and demonstrate their excellent photoelectric performances. More specifically, pyramidal semiconductor quantum dots (PSQDs) possess higher mobilities and longer lifetimes, which would be more suitable for photovoltaic devices requiring fast carrier transport. In addition, the linear polarization direction of exciton emission is easily controlled via the direction of magnetic field in PSQDs with C3v symmetry, so that all-optical multi-qubit gates based on electron spin as a quantum bit could be realized. Therefore, the use of PSQDs (e.g., InAs, GaN, InGaAs, and InGaN) as effective candidates for constructing optical quantum devices is examined due to the growing interest in optical quantum information processing. Pyramidal semiconductor nanorods (PSNRs) and pyramidal semiconductor nanowires (PSNWRs) also exhibit the more efficient separation of electron-hole pairs and strong light absorption effects, which are expected to be widely utilized in light-receiving devices. Finally, this review concludes with a summary of the current problems and suggestions for potential future research directions in the context of pyramidal low-dimensional semiconductors.

Contribution of magnons created in volume and within the surface in low-dimensional dilute magnetic semiconductor: eTBA Calculation for [formula omitted

The magnetic properties in low-dimensional dilute magnetic semiconductor system (Sn1−xCoxO2) are studied in the framework of extended Tight Binding Approximation (eTBA). According to the parameters of the solid, we established the Schrödinger equation to a single spin-wave state constructed as a sum of Bloch of atomic-type individual states of creations of spin deviations on a given site. We developed a tight binding interatomic potential that essentially represents the combined effect of direct exchange J and the magneto-crystalline anisotropy Δ. We demonstrated the existence of two kinds of magnons created in volume and in the surface of the Sn1−xCoxO2/SiO2 multilayers. We calculated the excitation spectrum of these two kinds of magnons. The magnetization per spin is also obtained. The calculated values are in very satisfactory agreement with the experimental measurements.

Optical Second Harmonic Generation of Low-Dimensional Semiconductor Materials.

In recent years, the phenomenon of optical second harmonic generation (SHG) has attracted significant attention as a pivotal nonlinear optical effect in research. Notably, in low-dimensional materials (LDMs), SHG detection has become an instrumental tool for elucidating nonlinear optical properties due to their pronounced second-order susceptibility and distinct electronic structure. This review offers an exhaustive overview of the generation process and experimental configurations for SHG in such materials. It underscores the latest advancements in harnessing SHG as a sensitive probe for investigating the nonlinear optical attributes of these materials, with a particular focus on its pivotal role in unveiling electronic structures, bandgap characteristics, and crystal symmetry. By analyzing SHG signals, researchers can glean invaluable insights into the microscopic properties of these materials. Furthermore, this paper delves into the applications of optical SHG in imaging and time-resolved experiments. Finally, future directions and challenges toward the improvement in the NLO in LDMs are discussed to provide an outlook in this rapidly developing field, offering crucial perspectives for the design and optimization of pertinent devices.

Core/Shell-Like Localized Emission at Atomically Thin Semiconductor-Au Interface.

Localized emission in atomically thin semiconductors has sparked significant interest as single-photon sources. Despite comprehensive studies into the correlation between localized strain and exciton emission, the impacts of charge transfer on nanobubble emission remains elusive. Here, we report the observation of core/shell-like localized emission from monolayer WSe2 nanobubbles at room temperature through near-field studies. By altering the electronic junction between monolayer WSe2 and the Au substrate, one can effectively adjust the semiconductor to metal junction from a Schottky to an Ohmic junction. Through concurrent analysis of topography, potential, tip-enhanced photoluminescence, and a piezo response force microscope, we attribute the core/shell-like emissions to strong piezoelectric potential aided by induced polarity at the WSe2-Au Schottky interface which results in spatial confinement of the excitons. Our findings present a new approach for manipulating charge confinement and engineering localized emission within atomically thin semiconductor nanobubbles. These insights hold implications for advancing the nano and quantum photonics with low-dimensional semiconductors.

Perovskite versus Nonperovskite: Modulating the Nature and Optical Properties of One-Dimensional Chiral Lead-Bromide Networks.

In the last 5 years, low-dimensional chiral metal-halide semiconductors have attracted great interest in the generation of chiroptical activity. Among this new family of materials, one-dimensional (1D) networks have appeared as the best candidates for strong circular dichroism (CD) and circularly polarized luminescence (CPL). Here, we present a new family of 1D chiral lead-bromide materials prepared from organic S/R/rac-1-hydroxypropyl-2-ammonium (S/R/rac-HP2A) cations. The presence or absence of polarity in the crystal structure as well as the perovskite or nonperovskite nature of the inorganic network depends on the initial stoichiometry of metal-halide salt and chiral amine during the crystallization. The perovskite-type networks exhibit strong CD and second harmonic generation (SHG) responses, while the nonperovskite compounds show the presence of polymorphism in the crystal phase and weak natural optical activity in the final material. These results underline the impact of synthetic conditions and thin film morphology on the structural and optical properties of metal-halide hybrid networks.

Adsorption of cadmium selenide clusters: A novel approach to enhance solar energy conversion using armchair graphene nanoribbons

Tailoring the electronic, optical, and transport properties of low-dimensional semiconductor materials is essential to improve the light-conversion efficiency of thin-film solar cell materials. Here, using first-principles calculations and non-equilibrium Green functions, we investigate the enhancement of optoelectronic and transport properties of armchair graphene nanoribbons (AGNRs) upon adsorption of cadmium selenide clusters. Upon adsorption of a CdSe diatomic molecule on an AGNR, the most energetically favorable configuration is the cadmium end sitting on top of a carbon atom. The corresponding electronic bandgap reduces ∼5 times with respect to that of the pristine system, thanks to the formation of a polaron state formed by the p-orbital of the selenide atom. Upon adsorption of CdSe cyclohexane molecules, the bandgap of this system slightly shrinks by 0.121 eV with respect to the pristine system. The charge accumulation induced by these clusters significantly enhances the absorption coefficient of the adsorbed systems, resulting in a red shift of the optical spectra toward the infrared region. More interestingly, by solving the Bethe–Salpeter equations with the Tamm–Dancoff approximation, we provide a direct link between the first-principles optical prediction and experimental observations. In addition, the electron transfer from these molecules to the hosted systems increases the transmission spectra in the vicinity of the Fermi level, leading to a remarkable electronic current passing through these scattering regions. These results highlight the role of cadmium selenide clusters in enhancing the light-to-energy conversion efficiency of next-generation solar cell devices.

Деградация проводимости низкоразмерных наноструктурированных полупроводниковых слоев при длительном протекании постоянного тока

Деградация проводимости низкоразмерных наноструктурированных полупроводниковых слоев при длительном протекании постоянного тока

Two-dimensional HfCr2N4 semiconductor with intrinsic room-temperature ferromagnetism and enhanced conductivity via electrostatic doping

Two-dimensional semiconductors with room-temperature intrinsic ferromagnetism and superior conductivity are crucial components for low-dimensional semiconductor spintronic devices. Based on density functional theory and Boltzmann transport theory, we investigate the electromagnetic and transport properties of the HfCr2N4 monolayer and modulate these properties via electrostatic doping. The HfCr2N4 monolayer is an intrinsic ferromagnetic semiconductor with a narrow band gap of 0.18 eV. The notably high Curie temperature of 719 K is highly desired for the practical applications of two-dimensional ferromagnetic materials. Under electrostatic doping, the HfCr2N4 monolayer maintains its ferromagnetic ground state, easy magnetization xy-plane, and high Curie temperature. Interestingly, owing to the narrow band gap of the HfCr2N4 monolayer, a significant enhancement in conductivity is observed at lower carrier doping concentrations, leading to a transition from a semiconductor to a half-metal. These unique features can be utilized to represent binary states ‘0’ and ‘1’. Our results indicate that the HfCr2N4 monolayer emerges as an ideal candidate for dual-gate field effect transistors.

Validation of minority carrier recombination lifetimes in low-dimensional semiconductors found by analytical photoresponses

It is a formidable challenge to find the minority carrier recombination lifetime in low-dimensional devices as low-dimensionality increases the surface recombination rate and often reduces the recombination lifetime to a scale of picoseconds. In this work, we demonstrated a simple but powerful method to quantitatively probe the minority carrier recombination lifetime in silicon nanowires or microwires by fitting the experimental photoresponses with our recently established analytical photoresponse principle of photoconductors. The nanowires were passivated with small molecules and Al2O3 to suppress surface recombination, which will increase the minority recombination lifetimes. As expected, the minority carrier recombination lifetime found by this approach increases by orders of magnitude. These wires were also made into PIN diodes, the leakage of which was reduced at least 1 order of magnitude after surface passivation by Al2O3. The minority recombination lifetime found from the leakage current of these devices is largely consistent with what we found from our analytical photoresponse principle. As a further step, we performed scanning photocurrent microscopy to find the minority diffusion length from which we found that the minority recombination lifetime is close to what we found from the analytical photoresponses. In short, this work validated that our analytical response principle is a reliable method to find the minority recombination lifetime in low-dimensional semiconductors.

A review of first-principles calculation methods for defects in semiconductors

Doping and defect control in semiconductors are essential prerequisites for their practical applications. First-principles calculations of defects based on density functional theory offer crucial guidance for doping and defect control. In this paper, the developments in the theoretical methods of first-principles semiconductor defect calculations are introduced. Firstly, we introduce the method of calculating the defect formation energy and finite-size errors to the formation energy caused by the supercell method. Then, we present corresponding image charge correction schemes, which include the widely used post-hoc corrections (such as Makov-Payne, Lany-Zunger, Freysoldt-Neugebauer-van de Walle schemes), the recently developed self-consistent potential correction which performs the image charge correction in the self-consistent loop for solving Kohn-Sham equations, and the self-consistent charge correction scheme which does not require an input of macroscopic dielectric constants. Further, we extend our discussion to charged defect calculations in low-dimensional semiconductors, elucidate the issue of charged defect formation energy divergence with the increase of vacuum thickness within the jellium model and introduce our theoretical model which solves this energy divergence issue by placing the ionized electrons or holes in the realistic host band-edge states instead of the virtual jellium state. Furthermore, we provide a brief overview of defect calculation correction methods due to the DFT band gap error, including the scissors operator, LDA+<i>U</i> and hybrid functionals. Finally, in order to describe the calculation of defect formation energy under illumination, we present our self-consistent two-Fermi-reservoir model, which can well predict the defect concentration and carrier concentration in the Mg doped GaN system under illumination. This work summarizes the recent developments regarding first-principles calculations of defects in semiconducting materials and low-dimensional semiconductors, under whether equilibrium conditions or non-equilibrium conditions, thus promoting further developments of doping and defect control within semiconductors.

Correcting charged supercell defect calculations in low-dimensional semiconductors

Correcting charged supercell defect calculations in low-dimensional semiconductors

Highly Responsive Switchable Broadband DUV-NIR Photodetector and Tunable Emitter Enabled by Uniform and Vertically Grown III-V Nanowire on Silicon Substrate for Integrated Photonics.

Low-dimensional semiconductor nanostructures, particularly in the form of nanowire configurations with large surface-to-volume-ratio, offer intriguing optoelectronic properties for the advancement of integrated photonic technologies. Here, a bias-controlled, superior dual-functional broadband light detecting/emitting diode enabled by constructing the aluminum-gallium-nitride-based nanowire on the silicon-platform is reported. Strikingly, the diode exhibits a stable and high responsivity (R) of over 200mAW-1 covering an extremely wide operation band under reverse bias conditions, ranging from deep ultraviolet (DUV: 254nm) to near-infrared (NIR: 1000nm) spectrum region. While at zero bias, it still possesses superior DUV light selectivity with a high off-rejection ratio of 106. When it comes to the operation of the light-emitting mode under forward bias, it can achieve large spectral changes from UV to red simply by coating colloid quantum dots on the nanowires. Based on the multifunctional features of the diodes, this study further employs them in various optoelectronic systems, demonstrating outstanding applications in multicolor imaging, filterless color discrimination, and DUV/NIR visualization. Such highly responsive broadband photodetector with a tunable emitter enabled by III-V nanowire on silicon provides a new avenue toward the realization of integrated photonics and holds great promise for future applications in communication, sensing, imaging, and visualization.

Energy-Band Engineering By Remote Doping of Self-Assembled Monolayers Leads to High-Performance Igzo/P-Si Heterostructure Photodetectors

Advancements in emerging technologies, such as autonomous driving, artificial intelligence, medical imaging, and augmented reality, have increased the demand for high-resolution image sensors to transmit further accurate color information. To meet the performance requirements of these applications, several research have been accelerating towards the utilization of emerging low-dimensional semiconductor materials, such as metal oxides, transition metal dichalcogenides, perovskites, and other organic materials.Among them, metal oxide semiconductors (MOSs) are potential candidates for developing high-performance photodetectors. It can be synthesized over large areas using a simple/low-temperature process and are compatible with conventional fabrication equipment. However, MOS-based photodetectors still have several limitations, 1) the presence of charge traps and operational instability on the oxide surface, which degrade photodetection performance, and 2) the absence of an appropriate doping technique for MOS has blocked to improve photodetection performance via materials characteristic modification method.In this study, we present a strategy to overcome these limitations and significantly enhance the performance of IGZO, which is representative of oxide semiconductor thin film, based photodetector with high operation stability and sustainability under ambient atmospheres. We utilized energy-band engineering through an octadecylphosphonic acid (ODPA) self-assembled-monolayer (SAM)-based doping treatment to enhance the photoelectric characteristics of IGZO/p-Si hetero-interfaced devices (ISH). The ODPA consists of a head group of the hydroxyl group, which forms the self-assembled covalent bond formation of R–P–O–substrate. Combining the ODPA SAM with the oxide surface of IGZO provided carrier concentration control based on their a dipole effect, and remain the performance and functionality through the surface encapsulation. As a result, under a light-emitting diode (LED) wavelength with an intensity of 3.9 mW, the proposed device exhibited remarkable photo-switching current ratio of 4.33 × 103 A/A and negative differential resistance (NDR) phenomenon. Espacially, the dark current of the ODPA treated ISH is decreased about 10 times lower than as-fabricated ISH, which shows the possibility of signal noise minimization. These performance improvement is expected to be derived from band properties modulation through IGZO layer annealing and ODPA doping. To clarify the doping effect of each treatment, we characterized the ODPA self-assembled monolayer using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM) to provide comprehensive analysis of the heterointerface effects. We also characterized the electrical properties of IGZO thin-film transistors (TFTs) based on variations of the annealing temperature to clarify the ODPA doping effect.We evaluated 156 ODPA-treated IGZO/p-Si heterostructure photodetectors, which were scaled for fabrication on a 4 inch wafer. The devices exhibited a 100% yield, and uniform current behavior in the dark state (0.20 ± 0.06 nA) and light state (0.87 ± 0.15 µA), owing to an evenly deposited IGZO layer and a simple-to-treat ODPA doping scheme. Furthermore, consecutive sweeps of 20,000 cycles verified excellent cycle-to-cycle endurance, resulting in highly robust photoelectric behaviors without operational failure. Additionally, the performance of the ODPA-treated, IGZO/p-Si heterostructure photodetector remained unchanged for 237 days without degradation under atmospheric exposure (relative humidity (RH) = 37–53 % and 20.6–23.1 °C). Acknowledgements This research was supported by funding supports from the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2020R1A2C1101647) and Korea government (MEST) (NRF-2017R1A2B3011222). Figure 1

Development of Daruharidra (Berberis aristata) Based Biogenic Cadmium Sulfide Nanoparticles: Their Implementation as Antibacterial and Novel Therapeutic Agents against Human Breast and Ovarian Cancer

aims: To illustrate novel preparations of cadmium sulfide nanoparticles (CdS NPs) taking economical and widely available daruharidra plant as a stabilizing agent for biogenic synthesis. It has shown to have a great efficiency in treating breast and ovarian cancer. We are focussing on daruharidra as a Herbal analogue that has low risks and side effects, are in expensive and show valuable results in due course of time as compared to conventional drugs. background: Cadmium sulfide (CdS) belongs to the semiconductor nanoparticles' II-VI group. Due to quantum captivity, these nanoparticles have one of kind optoelectronic properties that significantly differ from the bulk material. These nanoparticles having low-dimensional semiconductor properties are receiving significant attention in cancer treatment. In the fields of biochemistry, for the discovery of leads in cancer treatment, Daruharidra extracts in recent years are being explored. Chromatography techniques enable researchers to find hits in any plant extracts that could be used as an anticarcinogen or antitumorigenic agent in many cell lines. objective: The foremost objective of this study was to explore prospects of these nanoparticles as a potent anticancer agent. Human ovarian teratocarcinoma cells (PA1) and human breast cancer cells (MDAMB-231) were tested against these nanoparticles. method: MTT assay analysis to know the cytotoxic effect on cell lines when treated with increasing concentration of NPs was performed. The flow cytometry analysis was performed to understand the apoptosis and cell cycle arrest mechanism. the nanoparticles were also tested for their antibacterial potential by disc diffusion assay. result: IC50 for 24hour treatment was obtained as 97.34µg/ml and 809.75 µg/ml for ovarian and breast cancer cells respectively. It was found that treatment with CdS NPs lead to significant rise in early apoptotic cells i.e. from 2.53% to 13.5% and 3.67% to 12.6% in PA1 and MDAMB-231 cell line respectively. Also the NPs initiate the cell cycle arrest in G2/M phase with subG1 DNA damage in PA1 cells and G0/G1 arrest in MDAMB-231 cells. The NPs showed excellent results against both gram positive and negative bacteria. conclusion: Berberis sp extract can be an intelligible alternative that bears positive effects on people suffering from this disease. The availability of more specific herbal medicine should be more useful to prevent or treat cancer. The amalgation of plant extract and the CdS NPs could cause a paradigm shift in cancer therapy approach. The positive effects of the extract on cells of the human body and the easier targeted delivery can help the recovery of a patient as a whole. It is an unconventional approach. Thus, researchers are encouraged to conduct more research in this field and give credible verification suggesting the use of berberis plant extract in oncology. other: NA

Thermodynamic property of one-dimensional hydrogenic impurity in Nitride semiconductor quantum well

ABSTRACT The thermodynamic properties of one-dimensional (1-D) hydrogenic impurity in Nitride semiconductor quantum well have been investigated. Firstly, using a combination of the linear variational approach and the effective mass approximation, we obtain the eigen-energy of hydrogenic impurity states in AlN, GaN and InN quantum wells. Subsequently, we explore the quantum size effect on the thermodynamic properties of these low-dimensional semiconductor structures, revealing some novel and intriguing phenomena. It is found as the width of the quantum well is increased, the energy of hydrogenic impurity gets decreased, however, the thermodynamic parameters, such as the average energy, entropy and heat capacity of the hydrogenic impurity become increased. The physical origins of these peculiar phenomena are attributed to the competitive mechanism between the quantum confinement effect and Coulombic interaction between the electron and impurity. Finally, by conducting a comprehensive comparison of the thermodynamic parameters among GaN, InN, and AlN quantum wells, we propose an innovative strategy for modulating the thermodynamic properties of these low-dimensional semiconductor structures. This manipulation can be achieved not only through external factors such as temperature and quantum well size, but also by altering internal variables like the effective mass and relative dielectric constant of the semiconductor material. This study not only advances our understanding of the thermodynamic properties of hydrogenic impurities in semiconductor quantum wells, but also provides some theoretical guidance for practical applications in fields such as semiconductor physics, condensed matter physics, chemical physics, etc.

Boosting the photocatalytic activity of β-FeOOH catalyst for toluene oxidation by constructing internal electric field at 0D/1D homojunction interfaces

Photocatalytic degradation is considered as the most energy-efficient, environmentally benign, and effective method for treating low fraction organic contaminants. However, the photocatalysts still suffer from low utilization efficiency of visible-light and severe carrier recombination. Heterojunctions can resolve these two main problems in some extent but still be restrained by the low quality of hetero-interface. In this study, homojunction was constructed of β-FeOOH quantum dots and nanorods with the same lattice by a two-step precipitation method, to avoid the heterointerface with too many defects and possess good charge separation as a consequence. The catalysts were characterized by activity test, electron spin resonance, Mott-Schottky plots, photocurrent density tests and open-circuit potential measurements, etc. The results revealed that a strong internal electric fields (IEFs) was created at the interface of catalyst. Beneficently, the electron rearrangement leads to a more rational distribution of oxygen vacancies in the catalyst, resulting in more efficient dissociation of oxygen molecules and formation of active radicals, thus facilitating the efficient degradation of toluene. This study proposes a novel strategy to boosting the photocatalytic activity of low dimensional semiconductors via forming homojunction interfaces to improve their charge transfer.