Semiconductor Systems Research Articles

Properties of high to ultrahigh Si-doped GaN grown at 550 °C by flow modulated metalorganic chemical vapor deposition

The heterogeneous integration of III-nitride materials with other semiconductor systems for electronic devices is attractive because it combines the excellent electrical properties of the III-nitrides with other device platforms. Pursuing integration through metalorganic chemical vapor deposition (MOCVD) is desirable because of the scalability of the technique, but the high temperatures required for the MOCVD growth of III-nitrides (>1000 °C) are incompatible with direct heteroepitaxy on some semiconductor systems and fabricated wafers. Thus, the MOCVD growth temperature of III-nitride films must be lowered to combine them with other systems. In this work, 16 nm-thick Si:GaN films were grown by MOCVD at 550 °C using a flow modulation epitaxy scheme. By optimizing the disilane flow conditions, electron concentrations up to 5.9 × 1019 cm−3 were achieved, resulting in sheet resistances as low as 1070 Ω/□. Film mobilities ranged from 34 to 119 cm2 V−1 s−1. These results are promising for III-nitride integration and expand device design and process options for III-nitride-based electronic devices.

Theory of the in-plane photoelectric effect in quasi-one-dimensional electron systems

The in-plane photoelectric (IPPE) effect is a recently discovered [Sci. Adv. 8, eabi8398 (2022)] quantum phenomenon, which enables efficient detection of terahertz (THz) radiation in semiconductor structures with a two-dimensional (2D) electron gas. Here, we develop a theory of the IPPE effect in quasi-one-dimensional electron systems in which the width of the 2D conducting channel is so small that the transverse quantization energy is larger than the thermal energy. We calculate the THz photoresponse of such a system as a function of the THz frequency, control gate voltages, and geometrical parameters of the detector. We show that the transverse quantization of the electron motion manifests itself in oscillating gate-voltage dependences of the photocurrent, if the THz photon energy is less than the one-dimensional quantization energy. Results of the theory are applicable to any semiconductor systems with 2D electron gases, including III--V structures, silicon-based field effect transistors, and the novel 2D layered graphene-related materials.

Investigations of endurance and retention in tantalum oxide based memristor

Transparent neuromorphic electronics are gaining attention due the advantages of low-power operation, artificial self-learning synapses, and invisible circuits. Memristor plays a critical role in realizing these devices where the resistive state is continuously modified with application of external perturbations such as electric field, current, temperature and light. Endurance and retention are very important parameters for the repeatability and reliability of the device. Here, we have fabricated a memristor based on amorphous tantalum oxide thin films on transparent conducting oxide (TCO) substrate, using a physical vapor deposition technique. The structural quality of these films was confirmed by various characterization techniques namely Raman spectroscopy, UV–Vis spectroscopy, Scanning Electron Microscopy, Atomic Force Microscopy, and X-Ray Reflectivity. The device characteristics were measured using a semiconductor characterization system (SCS 4200). The influence of morphology, device thicknesses, and the nature of top and bottom electrodes has been investigated in detail to enhance the endurance and retention properties.

Atomistic Investigation on the Blocking Phenomenon of Crack Propagation in Cu Substrate Reinforced by CNT.

Recently, many researchers in the semiconductor industry have attempted to fabricate copper with carbon nanotubes for developing efficient semiconductor systems. In this work, tensile tests of a carbon-nanotube-reinforced copper specimen were conducted using the molecular statics method. The copper substrate utilized in the tensile tests had an edge half-crack, with the carbon nanotube located on the opposite side of the copper substrate. Subsequently, the effects of carbon nanotube radius were investigated. The mechanical properties of the copper/carbon nanotube composite were measured based on the simulation results, which indicated that the atomic behavior of the composite system exhibited the blocking phenomenon of crack propagation under tension. The fracture toughness of the composite system was measured using the Griffith criterion and two-specimen method, while the crack growth resistance curve of the system was obtained by varying the crack length. This study demonstrated that the mechanical reliability of copper can be improved by fabricating it with carbon nanotubes.

Funnel-shaped electronic structure and enhanced thermoelectric performance in ultralight Cx(BN)1−x biphenylene networks

Carbon biphenylene has stimulated substantial research because of extraordinary properties introduced by the metallic character, e.g., the ultrahigh electron thermal transport. Here, inspired by the synthesis of carbon biphenylene [Fan et al., Science 372, 852 (2021)], we identify the stability of ${\mathrm{C}}_{x}{(\mathrm{BN})}_{1\text{\ensuremath{-}}\mathrm{x}}$ biphenylene as $\text{CBN}$ and ${\mathrm{C}}_{4}\mathrm{BN}$ semiconductors with four-, six-, and eight-membered periodic rings of irregularly $s{p}^{2}$-hybridized atoms via structural searches. Unexpectedly, we confirm that $\text{CBN}$ biphenylene exhibits a peculiar funnel-shaped band structure, which is a direct consequence of the delocalization/localization of $\ensuremath{\pi}$ bonds formed by B-, N-, or C-${p}_{z}$ electrons. The band structure greatly improves the thermoelectric performance by enhancing the power factor, although the lattice thermal conductivity is relatively large after including four-phonon scattering resistance because of low atomic masses. The similar behaviors are absent in ${\mathrm{C}}_{4}\mathrm{BN}$ biphenylene because of the localization of $\ensuremath{\pi}$ bonds formed by C-${p}_{z}$ electrons, although with a stronger anharmonicity and thus a lower lattice thermal conductivity. The anomalous power factor can be explained by the constant $\ensuremath{\tau}$ approximation: the $p$-type doping controls the carrier group velocities and thus realizes the tunability of tensor ratio ${K}_{1}/{K}_{0}$. Our analysis suggests that the funnel-shaped electronic structure could be reproduced in two-dimensional semiconductor systems with the small electronegativity difference and the comparable stoichiometry. Our work realizes the thermoelectric improvement through controlling the shape of band structure, which provides insights for designing promising two-dimensional thermoelectric materials.

E-nose based on a high-integrated and low-power metal oxide gas sensor array

To improve the poor selectivity of a semiconductor gas-sensor system, an array of sensors can be utilized. However, this increases the system’s size and power consumption. To overcome these limitations, we propose a high-integrated and highly selective electronic nose (E-nose) comprising two independent gas-sensing elements on a low-power microhotplate (MHP). Pd-SnO2 nanoflowers and Pd-WO3 microparticles were prepared and printed on a bridge-structured MHP 20 µm apart and over an area of 110 µm × 45 µm. This was achieved using electrohydrodynamic inkjet printing aided by in-situ infrared laser curing to form an array of sensors. A power of 17 mW was required to increase the temperature of the MHP to 300 °C, which is the optimal operating temperature of the two gas sensors. Thus, a high response and low cross-sensitivity were achieved for hydrogen, ammonia, hydrogen–ammonia, ethanol, acetone, ethanol–acetone, toluene, and formaldehyde. A wavelet transform was used to reduce the noise and dimensionality of the signals from the gas-sensor array. Qualitative identification of the eight gases with an accuracy of 99.86% was achieved using the k-nearest neighbor (kNN) model. A p neighbors back propagation neural network (pN-BPNN) model was established to remove interfering samples to quantitatively estimate the gas concentration. The quantitative identification accuracy of pN-BPNN was higher than that of the standard back propagation neural network (BPNN) model with the average absolute percentage error of hydrogen detection in the range of 15–500 ppm, decreasing from 5.44% to 2.08%.

Unusual Spectrally Reproducible and High Q-Factor Random Lasing in Polycrystalline Tin Perovskite Films.

An unusual spectrally reproducible near-IR random lasing (RL) with no fluctuation of lasing peak wavelength is disclosed in polycrystalline films of formamidinium tin triiodide perovskite, which have been chemically stabilized against Sn2+ to Sn4+ oxidation. Remarkably, a quality Q-factor as high as ≈104 with an amplified spontaneous emission (ASE) threshold as low as 2µJcm-2 (both at 20K) are achieved. The observed spectral reproducibility is unprecedented for semiconductor thin film RL systems and cannot be explained by the strong spatial localization of lasing modes. Instead, it is suggested that the spectral stability is a result of such an unique property of Sn-based perovskites as a large inhomogeneous broadening of the emitting centers, which is a consequence of an intrinsic structural inhomogeneity of the material. Due to this, lasing can occur simultaneously in modes that are spatially strongly overlapped, as long as the spectral separation between the modes is larger than the homogeneous linewidth of the emitting centers. The discovered mechanism of RL spectral stability in semiconductor materials, possessing inhomogeneous broadening, opens up prospects for their practical use as cheap sources of narrow laser lines.

2023: The Golden Age of Semiconductors

<fig orientation="portrait" position="float" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <graphic orientation="portrait" position="float" xlink:href="chen-3243685.tif"/> </fig> The development of semiconductor circuits and systems has garnered unprecedented attention from governments worldwide as a result of reforms in the global semiconductor manufacturing and supply chain. This has been driven by concerns over the security of the supply chain, which has led to the introduction of various national initiatives, such as the United States’ CHIPS Act, aimed at promoting local manufacturing and R&D. The demand for semiconductors and its impact on related industries has resulted in over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 160 billion in capital expenditures in 2022. We are in the golden age of semiconductors. On the other hand, the global semiconductor market is expected to experience a 4% decline in 2023, reaching a total of about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 550 billion, marking the first annual contraction since 2019. The decrease in growth of the global semiconductor market is seen as a potential harbinger of broader economic troubles, leading to recent and planned job cuts at major companies within the industry.

Density functional theory computation of the intermolecular interactions of Al2@C24 and Al2@Mg12O12 semiconducting quantum dots conjugated with the glycine tripeptide.

The nature of intermolecular forces within semiconductor quantum dot systems can determine various physicochemical properties, as well as their functions, in nanomedical applications. The purpose of this study has been to investigate the nature of the intermolecular forces operating between Al2@C24 and Al2@Mg12O12 semiconducting quantum dots and the glycine tripeptide (GlyGlyGly), and also consider whether permanent electric dipole-dipole interactions play a significant role vis-à-vis these molecular systems. The energy computations, including the Keesom and the total electronic interactions and the energy decomposition, together with the quantum topology analyses were performed. Our results demonstrate that no significant correlation is found between the magnitude and orientation of the electrical dipole moments, and the interaction energy of the Al2@C24 and Al2@Mg12O12 with GlyGlyGly tripeptide. The Pearson correlation coefficient test revealed a very weak correlation between the quantum and the Keesom interaction energies. Apart from the quantum topology analyses, the energy decomposition consideration confirmed that the dominant share of the interaction energies was associated with the electrostatic interactions, yet both the steric and the quantum effects also made appreciable contributions. We conclude that, beside the electrical dipole-dipole interactions, other prominent intermolecular forces, such as the polarization attraction, the hydrogen bond, and the van der Waals interactions can also influence the interaction energy of the system. The findings of this study can be utilized in several areas in the field of nanobiomedicine, including the rational design of cell-penetrating and intracellular drug delivery systems using semiconducting quantum dots functionalized with a peptide.

How Many Excitons Can Combine?

Quantum diffusion Monte Carlo simulation demonstrated the formation of polyexcitons in two-dimensional multi-valley semiconductor systems, where all exciton pairs were energetically bound by equal-strength “chemical bonds.”

Formation of ZnO/CuO Heterostructures Based on Quasi-One-Dimensional Nanomaterials

Nanostructured metal oxides are of great interest both for advanced research and for a wide range of applications that contribute to the increasing demands of electronics, photonics, catalysis, sensorics, and other high-tech industries and are being actively researched and developed. One-dimensional nanocrystal arrays of copper and zinc oxides have become prominent in optoelectronic devices and energy conversion systems. However, although desirable improved properties have been demonstrated, the morphology of materials containing copper and zinc oxide nanowires is extremely sensitive to synthesis conditions and difficult to control. Studies focused on the morphology control of such quasi-one-dimensional materials are not numerous, so the consideration of this issue is still relevant. The characteristics of devices based on such oxide materials can be improved by taking advantage of nanoheterojunctions. A special feature is the possibility of forming a polycrystalline heterojunction in a system of semiconductors belonging to different crystalline syngonies. Currently, much attention is devoted to developing reliable methods of obtaining such nanomaterials, including those, based on processes exploiting novel physical effects. Possibilities of synthesis by pulse-periodic laser irradiation of arrays of quasi-one-dimensional ZnO nanostructures with varying micromorphology on metallic substrates, as well as the creation of ZnO/CuO heterostructures based on ZnO nanowires, were considered. The main distinguishing feature of this approach was the use of laser-induced vibrations to intensify diffusion processes in the solid phase of metallic materials as compared to the simple effects of laser beam heating. Expanding the area of application of the advanced method of creating oxide heterostructures requires a detailed and comprehensive study of new possibilities used to form structures with improved physical properties.

Extended π‐conjugated system in carbon nitride by incorporating pyridine rings and N vacancies for photocatalytic H2 evolution and H2O2 production

The extended π-conjugated system in polymer semiconductors holds a great potential in tuning the delocalized electrons for promoting photocatalytic efficiency. Herein, π-conjugate pyridine rings and nitrogen defects co-decorated polymer carbon nitride nanosheet (NCN-2AP-X) was constructed and applied in solar driven hydrogen (H2) and hydrogen peroxide (H2O2) production. Benefiting from synergistic effect of pyridine rings and N vacancies, the synthesized NCN-2AP photocatalyst with rich delocalized electrons indicates the extended light absorption range and improved carrier separation capability, particularly favoring the photocatalytic reactions. The optimal NCN-2AP-10 displayed an excellent H2 production rate of 2.55 mmol g−1 h−1 under visible-light irradiation with apparent quantum efficiency (AQE) of 9.79% at 420 nm. Moreover, a H2O2 production rate of 1.39 mmol L−1 h−1 was achieved by NCN-2AP-10 under monochromatic light (365 nm) irradiation. This work would provide a new view in designing the π-conjugated system incorporating metal-free photocatalysts for efficient H2 and H2O2 production.

МЕТОДИЧНИЙ АСПЕКТ ПРОВЕДЕННЯ СПОСТЕРЕЖЕНЬ ЗА ЗМІНОЮ ОБ’ЄМНОЇ КОНЦЕНТРАЦІЇ РАДОНУ В ЗАЛЕЖНОСТІ ВІД ГЕОГРАФІЧНО-СЕЙСМІЧНИХ ПАРАМЕТРІВ У РЕГІОНІ

The paper describes one of the methods of investigation of galvanomagnetic phenomena compound thin film semiconductor system AIVBVI. The resulting current-voltage characteristics of thin films PbTe: Sb and analyzed the basic parameters for thin films of different thicknesses using the method of Hall. The dependence of the film thickness PbTe:Sb on the mobility and concentration of major carriers.

Large photoluminescence enhancement in the chlorophyll from the energy transfer in perovskite–chlorophyll hybrid derivatives

Determining the photophysical processes for biomaterial–semiconductor systems has been beneficial for developing optoelectronic devices that exhibit biodegradability and biocompatibility. Here, we systematically investigated the optical properties and photophysical mechanisms of CsPbBr3 nanoparticles (NPs)-incorporated chlorophyll material. Steady-state photoluminescence (PL) studies reveal a large fluorescence enhancement in the chlorophyll once the perovskite was incorporated in the pristine chlorophyll with an associated PL quenching of the CsPbBr3 emission. A spectral overlap was measured from the PL and absorption spectra of CsPbBr3 NPs and chlorophyll indicative of a Förster-type resonance energy transfer (FRET). Using time-resolved PL, faster PL decay curves were observed from the CsPbBr3 NPs in the mixture suggesting that most of its energy was transferred to the chlorophyll. The corresponding Jablonski diagram was built and the energy transfer parameters, such as FRET efficiencies and transfer rates, were calculated to fully explain the FRET process. Slow PL degradation for the mixtures was also observed, highlighting the advantage of the FRET proposed. The demonstration of the photophysical mechanism in biomaterial–semiconductor systems is influential in improving the performance of emerging bio-inspired optoelectronic devices.

ОСОБЛИВОСТІ ДОСЛІДЖЕННЯ ГАЛЬВАНОМАГНІТНИХ ХАРАКТЕРИСТИК НАПІВПРОВІДНИКОВИХ ТОНКИХ ПЛІВОК

The paper describes one of the methods of investigation of galvanomagnetic phenomena compound thin film semiconductor system AIVBVI. The resulting current-voltage characteristics of thin films PbTe: Sb and analyzed the basic parameters for thin films of different thicknesses using the method of Hall. The dependence of the film thickness PbTe:Sb on the mobility and concentration of major carriers.

Self-organized structures induced by external white noise and nanosized levels of their formation in the non-crystalline As-S(Se) semiconductor systems

Discussed in this paper are the singularity and self-organizing effect of instability and randomness under the influence of external white noise on formation of non-crystalline materials. The random nature of the receiving medium together with the disorganizing effect was found to be capable to initiate formation of qualitatively new self-organized structures in non-crystalline solids. Also analyzed in the paper is the effect of a random temperature field applied to the melt during the cooling process in non-crystalline As-S(Se) semiconductor systems. The conditions for a non-crystalline system in a fluctuating external environment to adjust its properties to the average properties of the environment and to correspond to the deterministic case were identified. Furthermore, the conditions for non-additive reaction of the system to a random environment and formation of a new mode of energy conversion in the self-organized structure at the nanoscale level are determined. The spectrum of the structures created in this way is more diverse as compared to the spectrum corresponding to respective deterministic conditions.

Oxygen Vacancy‐Mediated Exciton Effect in Hierarchical BiOBr Enables Dichotomy of Energy Transfer and Electron Transfer in Photocatalysis

AbstractUsing solar energy through green and simple artificial photosynthesis systems are considered as a promising way to solve the energy and environmental crisis. However, one of the important primary steps of photosynthesis, i.e., energy transfer, is long being ignored especially in inorganic semiconducting systems due to the small exciton binding energies. Herein, the simultaneous interrogation of the charge transfer and energy transfer steps in a photoexcitation process is proposed by utilizing few‐layered nanosheet‐assembled hierarchical BiOBr nanotubes with rich oxygen vacancies (OVs) as efficient multifunctional photocatalysts. Benefiting from the integrated 1D/2D structure and abundant OV defects, the excitonic effect strikes a delicate balance in the optimized BiOBr photocatalyst, showing not only improved charge carrier separation and transfer but also enhanced exciton generation. As a result, the hierarchical BiOBr nanotubes exhibit high efficiency toward photocatalytic CO2 reduction with an impressive CO evolution rate of 135.6 µmol g−1 h−1 without cocatalyst or photosensitizer. The dominant reactive oxygen species of singlet oxygen (1O2) are discriminated for the first time, which originated from an energy transfer process, with electrophilic character, whereas the minor effect of superoxide anion radical (•O2−) with a nucleophilic rate‐determining step in the photocatalytic aerobic oxidation of sulfides.

Josephson effect as a signature of electron-hole superfluidity in bilayers of van der Waals heterostructures

We investigate a Josephson junction in an electron-hole superfluid in a double layer TMD heterostructure. Observation of a critical tunneling current is a clear signature of superfluidity. In addition, we find the BCS-BEC crossover physics in the narrow barrier region controls the critical current across the entire system. The corresponding critical velocity, which is measurable in this system, has a maximum when the excitations pass from bosonic to fermionic. Remarkably, this occurs for the density at the boundary of the BEC to BCS-BEC crossover regime determined from the condensate fraction. This provides, for the first time in a semiconductor system, an experimental way to determine the position of this boundary.

Graphene Metamaterial 3D Conformal Coating for Enhanced Light Harvesting

Silicon (Si) photovoltaic devices present possible avenues for overcoming global energy and environmental challenges. The high reflection and surface recombination losses caused by the Si interface and its nanofabrication process are the main hurdles for pursuing a high energy conversion efficiency. However, recent advances have demonstrated great success in improving device performance via proper Si interface modification with the optical and electrical features of two-dimensional (2D) materials. Firmly integrating large-area 2D materials with 3D Si nanostructures with no gap in between, which is essential for optimizing device performance, has rarely been achieved by any technique due to the complex 3D morphology of the nanostructures. Here we propose the concept of a 3D conformal coating of graphene metamaterials, in which the 2D graphene layers perfectly adapt to the 3D Si curvatures, leading to a universal 20% optical reflection decrease and a 60% surface passivation improvement. In a further application of this metamaterial 3D conformal coating methodology to standard Si solar cells, an overall 23% enhancement of the solar energy conversion efficiency is achieved. The 3D conformal coating strategy could be readily extended to various optoelectronic and semiconductor device systems with peculiar performance, offering a pathway for highly efficient energy-harvesting and storage solutions.

The Photo-stimulated Peltier Effect in Rectangular Quantum Wires under the Influence of Confined Phonons

Based on the kinetic equation method, the quantum Peltier effect has been theoretically studied under the influence of confined optical phonons in a rectangular quantum wire (RQW) of infinite high potential when placed in perpendicular electric and magnetic fields. There were complicated dependences of the analytical expression of the Peltier coefficient (PC) on quantities such as the size of the wires amplitude of the laser radiation, the cyclotron frequency of electrons and temperature of the system. Moreover, the presence of a strong electromagnetic wave (EMW) is also taken into account to determine the influence of confined phonons on the aforementioned effects. We have defined the analytical expressions for the kinetic tensors and PC. In detailed consideration, the quantum numbers m1, m2 were changed in order to characterize the influence of confined optical phonons. The results of setting the m1, m2 to zero showed that this case can be seen asthe unconfined optical phonon. This means that the confinement of the phonon affects the Peltier effect quantitatively and qualitatively. The theoretical results have been numerically evaluated and discussed for the GaAs/GaAsAl quantum wires. The change of the confinement and non-confinement phonons upon the change of the magnetic field shows that the height of the resonance peaks in the confinement case is about 4 times larger than the non-confinement case. The position of the resonance peak in the two cases are also shifted. The size of the wire in the case of the confinement phonon is more pronounced and stable than in the non-confinement case. The new results obtained can provide for completing the theory of the Peltier effect in low - dimensional semiconductor systems.&#x0D;