Semiconductor Single Crystals Research Articles

Growth process, defects, and dopants of bulk β-Ga2O3 semiconductor single crystals

Growth process, defects, and dopants of bulk β-Ga2O3 semiconductor single crystals

Ag nanoparticles at p-Si/ MAPbI3 perovskite interface: improved photo responsivity and response speed in photodetection

Although enhanced performances of photovoltaic devices by embedding metal nanoparticals in charge transport layer, doping into active layer bulk, decorating the active layer surface, and inserting at the interface between semiconductor and the electrode were reported, the effect of incorporating metal NPs at the interface of single crystal semiconductor and perovskite is rarely tackled. Herein the effects of incorporating Ag nanoparticals (AgNPs) at p-Si/MAPbI3 perovskite interface on the photodiode performances were investigated. The results showed that compared with reference device (without AgNPs) the photoresponsivity of the device incorporating AgNPs is greatly improved with the exception for light with wavelengths fall in the spectral range where AgNPs have strong optical absorption. This effect is extremely significant for relatively shorter wavelengths in visible region, and a maximal improvement of around 10.6 times in photoresponsivity was achieved. The physical origin of the exception for spectral range that AgNPs have strong optical absorption is the cancelation of scatter resulted enhancement through AgNPs by band-to-band absorption resulted reduction of photocurrent, in which the generated electron has energy near the fermi level and the hole has large effective mass, which relax by nonradiative recombination, thus making not contribution to the photocurrent. More importantly, the AgNP decorated device showed much faster photo response speed than reference device, and a maximal improvement of around 7.9 times in rise and fall time was achieved. These findings provide a novel approach for high responsive and high speed detection for weak light.

Liquid–liquid interface‐assisted growth of two‐dimensional organic semiconductor single crystals: Mechanisms, properties, and applications

AbstractTwo‐dimensional organic semiconductor single crystals (2D OSSCs) represent the promising candidates for the construction of high‐performance electronic and optoelectronic devices due to their ultrathin thicknesses, free of grain boundaries, and long‐range ordered molecular structures. In recent years, substantial efforts have been devoted to the fabrication of the large‐sized and layer‐controlled 2D OSSCs at the liquid‐liquid interface. This unique interface could act as the molecular flat and defect‐free substrate for regulating the nucleation and growth processes and enabling the formation of large‐sized ultrathin 2D OSSCs. Therefore, this review focuses on the liquid–liquid interface‐assisted growth methods for the controllable preparation of 2D OSSCs, with a particular emphasis on the advantages and limitations of the corresponding methods. Furthermore, the typical methods employed to control the crystal sizes, morphologies, structures, and orientations of 2D OSSCs at the liquid–liquid interface are discussed in detail. Then, the recent progresses on the 2D OSSCs‐based optoelectronic devices, such as organic field‐effect transistors, ambipolar transistors, and phototransistors are highlighted. Finally, the key challenges and further outlook are proposed in order to promote the future development of the 2D OSSCs in the field of the next‐generation organic optoelectronic devices.

Characterization of composition dependence of properties of a MgNiO-based MSM structure

In this study, the effect of Mg composition on structural and optical properties of MgxNi1-xO alloy thin film single crystal semiconductors as well as their implementation into Metal-Semiconductor–Metal (MSM) photodetector are studied. An 850 meV blue-shift of the bandgap is observed from 3.65 eV to 4.50 eV with increasing Mg composition from 0% to 67%. The deep ultraviolet/visible rejection ratio, which is the ratio of photosensitivity at a peak wavelength of 360 nm to that at 450 nm is found to be ∼58 for Mg composition of 67%. Mg rich (%67 Mg) alloy-based photodetector is found to have two orders smaller dark current and have higher spectral response compared to NiO-based one. Spectral responsivities for MgxNi1-xO photodetectors are determined as 415 mA W−1, 80 mA W−1, and 5.6 mA W−1 for Mg compositions of 67%, 21%, and 0% (reference-NiO), respectively. Furthermore, the detectivity of the photodetectors enhances as Mg composition increases and the highest detectivity of a magnitude of ∼1011 Jones is found for the photodetector with Mg composition of 67%.

Optimization of electron transmission on a 1D lattice

Finding optimal multi-layer heterostructure configurations that result in desired current–voltage characteristics requires physical control of electron scattering processes. It is shown how a one-dimensional tight-binding Hamiltonian combined with the adjoint method may be employed to explore this non-convex and non-intuitive design space. Such optimal parameter exploration has application to study of vertical electron transport through van der Waals stacked few-layer quantum materials and nano-scale single-crystal semiconductor heterostructures.

Highly-Polarized Solar-Blind Ultraviolet Organic Photodetectors.

Developing high-performance polarization-sensitive ultraviolet photodetectors is crucial for their application in military remote sensing, detection, bio-inspired navigation, and machine vision. However, the significant absorption in the visible light range severely limits the application of polarization-sensitive ultraviolet photodetectors, such as high-quality anti-interference imaging. Here, based on a wide-bandgap organic semiconductor single crystal (trans-1,2-bis(5-phenyldithieno[2,3-b:3',2'-d]thiophen-2-yl)ethene, BPTTE), high-performance polarization-sensitive solar-blind ultraviolet photodetectors with a dichroic ratio close to 4.26 are demonstrated. The strong anisotropy of 2D grown BPTTE single crystals in molecular vibration and optical absorption is characterized by various techniques. Under voltage modulation, stable and efficient detection of polarized light is demonstrated, attributed to the intrinsic anisotropy of transition dipole moment in the bc crystal plane, rather than other factors. Finally, high-contrast polarimetric imaging and anti-interference imaging are successfully demonstrated based on BPTTE single crystal photodetectors, highlighting the potential of organic semiconductors for polarization-sensitive solar-blind ultraviolet photodetectors.

Charge redistribution of a spatially differentiated ferroelectric Bi4Ti3O12 single crystal for photocatalytic overall water splitting

Artificial photosynthesis is a promising approach to produce clean fuels via renewable solar energy. However, it is practically constrained by two issues of slow photogenerated carrier migration and rapid electron/hole recombination. It is also a challenge to achieve a 2:1 ratio of H2 and O2 for overall water splitting. Here we report a rational design of spatially differentiated two-dimensional Bi4Ti3O12 nanosheets to enhance overall water splitting. Such a spatially differentiated structure overcomes the limitation of charge transfer across different crystal planes in a single crystal semiconductor. The experimental results show a redistribution of charge within a crystal plane. The resulting photocatalyst produces 40.3 μmol h–1 of hydrogen and 20.1 μmol h–1 of oxygen at a near stoichiometric ratio of 2:1 and a solar-to-hydrogen efficiency of 0.1% under simulated solar light.

Crack Catcher AI – Enabling smart fracture mechanics approaches for damage control of thin silicon cells or wafers

Silicon has been one among a few key technologically important materials especially in our modern world. Silicon, especially in its current most useful forms (thin layers), is a brittle material by nature. Thin silicon cells crack easily during manufacturing assembly. Every crack is a defect in any PV manufacturing lines, and if let to grow/propagate it will lead to reliability and quality issues with time. Nevertheless, the global silicon solar PV industry is aggressively reducing the cost of solar PV systems through cutting down the thickness of silicon solar cells. Cell cracks immediately lower PV module efficiency and can lead to premature aging of the entire module. The “Crack Catcher AI” was our research joint collaboration's entry in the Department of Energy (DOE)'s American-Made Solar Innovation competition in 2022 (Round 6) which later was selected as the national semifinalists and won an award announced by DOE in December 2022. It uses smart stress sensing and smart fracture prediction approaches utilizing fundamental fracture mechanics and big data analytics to reduce crack defects and enhance long-term durability/reliability of PV products/devices. Smart Stress Sensing uses a novel laser-based curvature methodology for fast in-line stress metrology in manufacturing lines. Smart Fracture Prediction uses Artificial Intelligence (AI) for defect control metrology and yield enhancement in PV production lines. It is based on monocrystalline silicon used in solar PV industries, but all scientific principles utilized and technological innovations developed in this article would be applicable as well for single crystal silicon semiconductor wafers.

Tuning magnetic and optical properties in Mn x Zn1−x PS3 single crystals by the alloying composition

The exploration of two-dimensional (2D) antiferromagnetic (AFM) materials has shown great promise and interest in tuning the magnetic and electronic properties as well as studying magneto-optical effects. The current work investigates the control of magneto-optical interactions in alloyed Mn x Zn1−x PS3 lamellar semiconductor single crystals, with the Mn/Zn ratio regulating the coupling strength. Magnetic susceptibility results show a retention of AFM order followed by a decrease in Néel temperatures down to ∼40% Mn concentration, below which a paramagnetic behavior is observed. Absorption measurements reveal an increase in bandgap energy with higher Zn(II) concentration, and the presence of Mn(II) d-d transition below the absorption edge. DFT + U approach qualitatively explained the origin and the position of the experimentally observed mid band-gap states in pure MnPS3, and corresponding peaks visible in the alloyed systems Mn x Zn1‒x PS3. Accordingly, emission at 1.3 eV in all alloyed compounds results from recombination from a 4T1g Mn(II) excited state to a hybrid p-d state at the valence band. Most significant, temperature-dependent photoluminescence (PL) intensity trends demonstrate strong magneto-optical coupling in compositions with x > 0.65. This study underscores the potential of tailored alloy compositions as a means to control magnetic and optical properties in 2D materials, paving the way for advances in spin-based technologies.

INVESTIGATION OF THE ROLE OF METAL IN NON-ALLOY METAL-SEMICONDUCTOR (Si) CONTACT

In the paper is shown that the metal is a more active partner in Schottky diodes (SD) based on metal-semiconductor contact (MSC) from the series of semiconductor devices. It is shown the structural inhomogeneity of the interface, as a result of which the MSC as a parallel connection of numerous subdiodes having different parameters. To reveal the inhomogeneity of the metal on the properties of the MSC, the dependence of the barrier height of Schottky diodes on the contact area was investigated. It was assumed that in the case of a contact of a single-crystal semiconductor with a polycrystalline metal, the degree of inhomogeneity and accordingly, the number of subcontacts grow with increasing area.

Fabrication of Single-Crystal Violet Phosphorus Flakes For Ultrasensitive Photodetection.

Violet phosphorus (VP) has attracted a lot of attention for its unique physicochemical properties and emerging potential in photoelectronic applications. Although VP has a van der Waals (vdW) structure similar to that of other 2D semiconductors, direct synthesis of VP on a substrate is still challenging. Moreover, optoelectronic devices composed of transfer-free VP flakes have not been demonstrated. Herein, a bismuth-assisted vapor phase transport technique is designed to grow uniform single-crystal VP flakes on the SiO2/Si substrate directly. The size of the crystalline VP flakes is an order of magnitude larger than that of previous liquid-exfoliated samples. The photodetector fabricated with the VP flakes shows a high responsivity of 12.5 A W-1 and response/recovery time of 3.82/3.03ms upon exposure to 532nm light. Furthermore, the photodetector shows a small dark current (<1 pA) that is beneficial to high-sensitivity photodetection. As a result, the detectivity is 1.38×1013 Jones that is comparable with that of the vdW p-n heterojunction detector. The results reveal the great potential of VP in optoelectronic devices as well as the CVT technique for the growth of single-crystal semiconductor thin films.

Epitaxy of wafer-scale single-crystal MoS2 monolayer via buffer layer control

Monolayer molybdenum disulfide (MoS2), an emergent two-dimensional (2D) semiconductor, holds great promise for transcending the fundamental limits of silicon electronics and continue the downscaling of field-effect transistors. To realize its full potential and high-end applications, controlled synthesis of wafer-scale monolayer MoS2 single crystals on general commercial substrates is highly desired yet challenging. Here, we demonstrate the successful epitaxial growth of 2-inch single-crystal MoS2 monolayers on industry-compatible substrates of c-plane sapphire by engineering the formation of a specific interfacial reconstructed layer through the S/MoO3 precursor ratio control. The unidirectional alignment and seamless stitching of MoS2 domains across the entire wafer are demonstrated through cross-dimensional characterizations ranging from atomic- to centimeter-scale. The epitaxial monolayer MoS2 single crystal shows good wafer-scale uniformity and state-of-the-art quality, as evidenced from the ~100% phonon circular dichroism, exciton valley polarization of ~70%, room-temperature mobility of ~140 cm2v−1s−1, and on/off ratio of ~109. Our work provides a simple strategy to produce wafer-scale single-crystal 2D semiconductors on commercial insulator substrates, paving the way towards the further extension of Moore’s law and industrial applications of 2D electronic circuits.

Дослідження розподілу кисню по довжині монокристалів кремнію, легованих компонентами з різним типом провідності

The purpose of the article is the study of convective flows and their influence on the growth of single crystals of silicon by the Czochralsky method from a large melt, which contributes to the emergence of non-stationary convection. Therefore, simulation of convection for the growth of silicon single crystals is an important step in the development of conditions for the growth of perfect single crystals. Silicon substrates are used to manufacture more than 90% of semiconductor devices and solar cells. A special role in the development of electronics is played by monocrystalline silicon, which is used for the manufacture of semiconductor devices and integrated microcircuits. The main requirements for the development of technology for the production of silicon substrates is an increase in quality at a decrease in cost. Promising technologies of 10-nm size and 3D-transistor structures significantly increase the requirements for uniformity of distribution of components, including layering in silicon single crystals. For the mathematical modeling of convective flows, melt flows were considered for a cylindrical crucible with a radius of 150 mm at a melt height of up to 40 mm. Such parameters ensure stationary convection in molten silicon. Methods of reducing stratification have been studied and developed for more than 50 years, but have not yet found a definitive solution. This method of single crystal growth is the most controlled and allows to influence the convective flows in the silicon melt below the phase interface with ultrasonic waves in the megahertz range. The effectiveness of using ultrasound in the extraction of semiconductor single crystals depends on the creation of special conditions for introducing them into the melt. &#x0D; Reducing the influence of oxygen on the electrophysical properties of silicon single crystals is an intractable problem of silicon technology. One of the ways to solve this problem is alloying with an isomorphic impurity, for example, tin. The development of a method of doping single crystals of silicon with tin requires determination of its concentration in the liquid and solid phases

Magnetic field modulation effect on photoelectric effect and its explanation in BiFe0.9Ni0.1O3/n-Si multiferroic heterojunction

This paper reports a heterojunction laminate consisting of Ni doped BiFeO3 thin film and n-type single crystal silicon semiconductor, in which the repeatable modulation effect on the photoelectric properties were achieved by applying external magnetic fields. More obviously, the response of photocurrent and photovoltage to the magnetic field is perfectly linear. This functional effect of sensing is mainly related to the guidance of the magnetic field to the photogenerated carrier transfer process in the heterojunction. The linear relationships between magnetic field and photocurrent, magnetic field and photovoltage have been proved through the derivation of the formulas. The heterojunction perfectly combines the functions of the sensor and the controller to reflect both the intensity of the magnetic field and the intensity of the light in the environment. This work provides an alternative and facile way to realize the multi-degree of freedom control for electrical signal and practicability of multifunctional devices.

Optical activation of implanted lanthanoid ions in aluminum nitride semiconductors by high temperature annealing

Lanthanoid (Ln)-doped aluminum nitride (AlN) semiconductors are one candidate for optoelectric devices and single photon sources, although their optical properties are less understood. We clarify the room temperature optical properties of Ln ion implanted single crystal AlN semiconductors and their changes upon thermal annealing by up to 1700 °C. Photoluminescence (PL), cathodoluminescence (CL), and time-resolved PL for praseodymium (Pr), europium (Eu), and neodymium (Nd) ion implanted AlN are analyzed. Recovery of implantation induced damages and thermal diffusion of implanted Ln ions by thermal annealing are also investigated. Our systematic studies reveal that there is a trade-off between optical activation of implanted Ln ions due to recovery of implantation damage and deactivation (quenching) due to complex formation and aggregation of Ln ions. The PL intensity of implanted Pr ions increases with increasing annealing temperature in the case of high-dose implantation (above 1020 cm-3), whereas it rather decreases in the case of low-dose implantation (below 4 × 1019 cm-3). However, the PL intensity is significantly reduced after annealing at 1700 °C in both cases, indicating that the quenching factor is dominant in this temperature range.

Room-temperature ferromagnetism in Fe-doped SnSe bulk single crystalline semiconductor

The quest for pragmatic room-temperature (RT) magnetic semiconductors (MSs) with a suitable bandgap constitutes one of the contemporary opportunities to be exploited. This may provide a materials platform for to bring new-generation ideal information device technologies into real-world applications where the otherwise conventionally separately utilized charge and spin are simultaneously exploited. Here we present RT ferromagnetism in an Fe-doped SnSe (Fe:SnSe) van der Waals (vdW) single crystalline ferromagnetic semiconductor (FMS) with a semiconducting bandgap of ∼1.19 eV (comparable to those of Si and GaAs). The synthesized Fe:SnSe single crystals feature a dilute Fe content of <1.0 at%, a Curie temperature of ∼310 K, a layered vdW structure nearly identical to that of pristine SnSe, and the absence of in-gap defect states. The Fe:SnSe vdW diluted magnetic semiconductor (DMS) single crystals are grown using a simple temperature-gradient melt-growth process, in which the magnetic Fe atom doping is realized uniquely using FeI2 as the dopant precursor whose melting point is low with respect to crystal growth, and which in principle possesses industrially unlimited scalability. Our work adds a new member in the family of long-searching RT magnetic semiconductors, and may establish a generalized strategy for large-volume production of related DMSs.

THE CHEMICAL ETCHING OF CdTe, ZnxCd1-xTe and CdxHg1-xTe SINGLE CRYSTALS WITH HNO3 – KI – DIMETHYLFORMAMIDE SOLUTIONS

The chemical dissolution of CdTe single crystals, ZnxCd1-xTe and CdxHg1-xTe solid solutions in HNO3 – KI – dimethylformamide solutions has been investigated under reproducible hydrodynamic conditions for the first time. It is shown that the etching compositions of this system are cheaper, create a less aggressive environment, are more stable over time and are more ecologically safe. The diagrams «solution composition versus dissolution rate» has been plotted and the concentration limits of polishing etchant have been determined. Chemical-dynamic polishing with the investigated solutions can be carried out with a volume content of HNO3 9-15 %, while the polishing speed the surface of CdTe single crystals, ZnxCd1-xTe and CdxHg1-xTe solid solutions is within 1.6-2.5 μm/min. The dependence of the ions concentration that passed into the solution after the interaction of solid solutions ZnxCd1-xTe with the investigated etchants, versus the content of the oxidant in the etchant has been determined, and it was shown that the content of ions in the solution corresponds to the molar ratio in the semiconductor and indicates uniform dissolution of the surface. Based on the results of kinetic study, the apparent activation energy of the polishing was calculated for a solution of the composition (in vol. %): 12 НNO3 + 88 KI (DMF), which does not exceed 15.1 kJ/mol for СdTe and 7.7 kJ/mol for solid solutions on its basis, which indicates the limitation of the process by diffusion stages. The effect of the lactic acid and the nature of the semiconductors on the kinetics of chemical-mechanical polishing of the studied single crystals were determined. When the polishing solution is diluted with organic acid to 40 vol. %, the speed of chemical and mechanical polishing decreases from 3.5 to 0.5 μm/min. The compositions of etching mixtures and modes of implementation of chemical-dynamic polishing, which is recommended to be carried out in a suitable installation at the temperature 293 K and the disk rotation speed 82 min‑1, and chemical-mechanical polishing of the mention above semiconductor single crystals with the addition of lactic acid and polishing rates of 3.5-0.5 μm/min.

High-entropy halide perovskite single crystals stabilized by mild chemistry.

Although high-entropy materials are excellent candidates for a range of functional materials, their formation traditionally requires high-temperature synthetic procedures of over 1,000 °C and complex processing techniques such as hot rolling1-5. One route to address the extreme synthetic requirements for high-entropy materials should involve the design of crystal structures with ionic bonding networks and low cohesive energies. Here we develop room-temperature-solution (20 °C) and low-temperature-solution (80 °C) synthesis procedures for a new class of metal halide perovskite high-entropy semiconductor (HES) single crystals. Due to the soft, ionic lattice nature of metal halide perovskites, these HES single crystals are designed on the cubic Cs2MCl6 (M=Zr4+, Sn4+, Te4+, Hf4+, Re4+, Os4+, Ir4+ or Pt4+) vacancy-ordered double-perovskite structure from the self-assembly of stabilized complexes in multi-element inks, namely free Cs+ cations and five or six different isolated [MCl6]2- anionic octahedral molecules well-mixed in strong hydrochloric acid. The resulting single-phase single crystals span two HES families of five and six elements occupying the M-site as a random alloy in near-equimolar ratios, with the overall Cs2MCl6 crystal structure and stoichiometry maintained. The incorporation of various [MCl6]2- octahedral molecular orbitals disordered across high-entropy five- and six-element Cs2MCl6 single crystals produces complex vibrational and electronic structures with energy transfer interactions between the confined exciton states of the five or six different isolated octahedral molecules.

Wafer-Scale Epitaxial Growth of Two-dimensional Organic Semiconductor Single Crystals toward High-Performance Transistors.

The success of state-of-the-art electronics and optoelectronics relies heavily on the capability to fabricate semiconductor single-crystal wafers. However, the conventional epitaxial growth strategy for inorganic wafers is invalid for growing organic semiconductor single crystals due to the lack of lattice-matched epitaxial substrates and intricate nucleation behaviors, severely impeding the advancement of organic single-crystal electronics. Here, an anchored crystal-seed epitaxial growth method for wafer-scale growth of 2D organic semiconductor single crystals is developed for the first time. The crystal seed is firmly anchored on the viscous liquid surface, ensuring the steady epitaxial growth of organic single crystals from the crystal seed. The atomically flat liquid surface effectively eliminates the disturbance from substrate defects and greatly enhances the 2D growth of organic crystals. Using this approach, a wafer-scale few-layer bis(triethylsilythynyl)-anthradithphene (Dif-TES-ADT) single crystal is formed, yielding a breakthrough for organic field-effect transistors with a high reliable mobility up to 8.6 cm2 V-1 s-1 and an ultralow mobility variable coefficient of 8.9%. This work opens a new avenue to fabricate organic single-crystal wafers for high-performance organic electronics.

Growth of single crystal Sb2S3 semiconductor pillars by sol-gel method

The binary compound semiconductor Sb2S3 was fabricated on solid substrate by spin coating based on a sol-gel method. In this study, it was observed that crystallinity appeared differently depending on the type of substrate material used to fabricate the Sb2S3 structure, and this mechanism was investigated. As the substrate, bare FTO glass and FTO glass coated with Mo, Ni, and Au were used. In the case of Sb2S3 grown on bare FTO glass and FTO glass coated with Mo, crystals are formed in-plane, whereas in the case of Sb2S3 grown on FTO glass substrate coated with FCC-structured metals such as Au and Ni, crystals are formed out-of-plane. It was observed that the single crystal growth of rectangular pillar-shaped Sb2S3 was closely related to the formation of regularly ordered compounds at the interface between the Sb2S3 pillar and the FCC metal substrate.