Design Of Semiconductor Devices Research Articles

Coupling Response of Piezoelectric Semiconductor Composite Fiber under Local Temperature Change

This paper details the thermal–mechanical–electrical response of a piezoelectric semiconductor (PS) composite fiber composed of a PS layer and two piezoelectric layers under local temperature change. The phenomenological theory of thermal piezoelectric semiconductors (PSs) is adopted to obtain the analytical solution for each field in the composite fiber under local temperature change. Our findings reveal that such temperature fluctuations induce local polarization, leading to the formation of local potential barriers and potential wells that effectively impede the flow of low-energy electrons along the fiber. Furthermore, the initial carrier concentration and geometric parameters of the composite fiber exert significant influence on its individual fields. The results contribute to the structural design and practical application of piezoelectric semiconductor devices.

Modifying electronic and optical properties of violet phosphorus through variable fluorine coverage.

We present a comprehensive investigation of the electronic properties of fluorinated monolayer violet phosphorus using first-principles calculations. Our results reveal a strong dependence of the electronic properties on the different fluorine coverages of fluorination. As the fluorine coverage increases, monolayer violet phosphorus undergoes a significant transition from a wide direct bandgap semiconductor to a narrow indirect bandgap semiconductor. Moreover, both semi-fluorinated and fully fluorinated monolayer violet phosphorus exhibit advantageous semiconducting characteristics, with a tunable bandgap of 0.50 ~ 1.04 eV under biaxial strain ranging from -6% to 6%. Notably, the fully fluorinated monolayer violet phosphorus demonstrates a higher coefficient of light absorption within the visible range. Therefore, our findings highlight the tunability of monolayer violet phosphorus properties through the absorption of various fluorine coverages, providing valuable insights for the design and development of novel semiconductor devices based on this material.

Machine Learning-based Inverse Design Model of a Transistor

Objectives: To develop an inverse design model for transistors, utilizing machine learning algorithms to predict key design parameters specifically, the length and width based on specified gain and bandwidth requirements. And to conduct a comprehensive comparative analysis with existing literature, evaluating the efficacy and novelty of the proposed model in the context of semiconductor engineering challenges and methodologies. Methods: The comprehensive dataset, comprising 30,000 values generated through LTspice simulations, forms the basis for training the machine learning model. Utilizing a Random Forest regressor as the base model and a multi-output regressor as the main model, the project involves extensive data analysis, model development, and iterative fine-tuning. Findings: The outcomes demonstrate the efficacy of the developed model in accurately predicting transistor dimensions. Performance metrics, including Mean Absolute Error (MAE), Mean Squared Error (MSE), and R-squared, highlight the precision of the model in fulfilling the specified objectives. Novelty: This study introduces a novel approach to semiconductor device design optimization, showcasing the potential of machine learning to streamline the inverse design process. The use of a multi-output regressor, feature engineering, and fine-tuning through log transformation contribute to the innovative nature of the developed model. Keywords: Machine Learning (ML) model, Random Forest regressor, multi­output regressor, Feature engineering, Fine­tuning

Plunger gate effects on magneto transport in double-top gate spin-orbit devices

A propagation matrix method is used to investigate the quantum conductance of an n-type double-top gate device under a strong Rashba-Zeeman coupling interaction. The effects of a plunger gate potential and the total top gate length on the magneto conduction properties are investigated. Transcendental equations and analytical formulas are derived to accurately predict the resonance state and hole-like bound state structures. Furthermore, the effect of the distance of the two top gates from the plunger gate is examined for both symmetric and asymmetric structures. The analytical technique employed in this study provides an accurate and reliable approach for calculating the conductance of the quantum transport and is therefore beneficial for the design of n-type semiconductor devices.

Synthesis and investigation of the structure, thermal, optical, and electrical properties of poly (indol-thiazolo-thiadiazole) derivatives at room temperature

This research work is intended for the novel synthesis and study of structural, thermal, optical, electrical, and dielectric properties of semiconductor poly (2-amino-5-(1H-indolyl)-5H-thiazolo[4,3-b]-1,3,4-thiadiazole) (PAITTD) and its N-substituted indole derivatives with a side chain containing chlorobenzoyl (PACBITTD) and bromobenzene sulphonyl (PABBSITTD). The characterization techniques such as H1NMR, FTIR, SEM, and TGA/DSC ensured the structural and thermal properties of the as-synthesized polymers. In addition, the molecular weight of the PAITTD, PACBITTID, and PABBSITTD was calculated via H1NMR technique. The optical band gap as obtained from the absorbance study was found to be in the range of 1.5 eV to 2.58 Ev. Moreover, the ground-state geometries and the absorption wavelengths for the studied compounds were investigated by DFT and TD-DFT, where the theoretical results show coincidence with these of the experimental where the calculated (λmax) values are approximately near to the experimental (λmax) values for the PAITTD, PACBITTID, and PABBSITTD. The impedance ac conductivity and dielectric properties of the PAITTD, PACBITTID, and PABBSITTD were performed in the frequency ranges from 20 Hz to 10 MHz at room temperature, where their values were 3.0 × 10−7, 8.7 × 10−7, and 2.6 × 10−6, respectively. The Nyquist plot confirmed the presence of both grain and grain boundary effects for conducting PAITTD, PACBITTID, and PABBSITTD, and Double relaxation behavior was also observed. The variation of ac conductivity with frequency obeys the modification of Jonscher’s universal power law (JUPL). Based on the optical and electrical properties, synthetic PAITTD, PACBITTID, and PABBSITTD are promising materials in the design of optoelectronic semiconductor devices.

Effects of Thermal Boundary Resistance on Thermal Management of Gallium-Nitride-Based Semiconductor Devices: A Review.

Wide-bandgap gallium nitride (GaN)-based semiconductors offer significant advantages over traditional Si-based semiconductors in terms of high-power and high-frequency operations. As it has superior properties, such as high operating temperatures, high-frequency operation, high breakdown electric field, and enhanced radiation resistance, GaN is applied in various fields, such as power electronic devices, renewable energy systems, light-emitting diodes, and radio frequency (RF) electronic devices. For example, GaN-based high-electron-mobility transistors (HEMTs) are used widely in various applications, such as 5G cellular networks, satellite communication, and radar systems. When a current flows through the transistor channels during operation, the self-heating effect (SHE) deriving from joule heat generation causes a significant increase in the temperature. Increases in the channel temperature reduce the carrier mobility and cause a shift in the threshold voltage, resulting in significant performance degradation. Moreover, temperature increases cause substantial lifetime reductions. Accordingly, GaN-based HEMTs are operated at a low power, although they have demonstrated high RF output power potential. The SHE is expected to be even more important in future advanced technology designs, such as gate-all-around field-effect transistor (GAAFET) and three-dimensional (3D) IC architectures. Materials with high thermal conductivities, such as silicon carbide (SiC) and diamond, are good candidates as substrates for heat dissipation in GaN-based semiconductors. However, the thermal boundary resistance (TBR) of the GaN/substrate interface is a bottleneck for heat dissipation. This bottleneck should be reduced optimally to enable full employment of the high thermal conductivity of the substrates. Here, we comprehensively review the experimental and simulation studies that report TBRs in GaN-on-SiC and GaN-on-diamond devices. The effects of the growth methods, growth conditions, integration methods, and interlayer structures on the TBR are summarized. This study provides guidelines for decreasing the TBR for thermal management in the design and implementation of GaN-based semiconductor devices.

Charge Transport Mechanism of Organic Semiconductors Based on Molecular Dynamics Simulation

The aim of this paper is to investigate the charge transport mechanism in organic semiconductors based on molecular dynamics simulation. Molecular dynamics simulation, as an effective computational method, can reveal the microscopic mechanism of charge transport in organic semiconductors. The basic principles and methods of molecular dynamics simulation will be introduced in the paper, and its application in studying charge transport in organic semiconductors will be discussed. Through the simulation analysis, the effects of key parameters such as intermolecular interactions, carrier mobility and electron transport on the performance of organic semiconductor devices can be revealed, providing guidance for the design and optimization of organic semiconductor devices.

Fully-coupled piezoelectric field in the semiconductor heterostructure with an ellipsoidal anisotropic inhomogeneity

The elastic and piezoelectric fields induced by misfit strain in semiconductor heterostructures are crucial for the design of semiconductor devices. This work formulates analytically the fully-coupled piezoelectric field in the heterostructure with a general anisotropic inhomogeneity. The application of the ellipsoidal inhomogeneity is numerically solved by implementations of the generalized Green's function and its derivative as well as their surface integrals. Elaborations will be made on the similarities and differences for the usage of the inclusion and inhomogeneity in the fully-coupled analysis, along with some discussions about the shape and size effects in the end.

Photo-thermo-piezo-elastic waves in semiconductor medium subject to distinct two temperature models with higher order memory dependencies

PurposeThis study aims to examine the impacts of higher memory dependencies on a novel semiconductor material that exhibits generalized photo-piezo-thermo-elastic properties. Specifically, the research focuses on analyzing the behavior of the semiconductor under three distinct temperature models.Design/methodology/approachThe study assumes a homogeneous and orthotropic piezo-semiconductor medium during photo-thermal excitation. The field equations have been devised to encompass higher order parameters, temporal delays and a specifically tailored kernel function to address the problem. The eigenmode technique is used to solve these equations and derive analytical expressions.FindingsThe research presents graphical representations of the physical field distribution across different temperatures, higher order plasma heat conduction models and time. The results reveal that the amplitude of the distribution profile is markedly affected by factors such as the memory effect, time, conductive temperature and spatial coordinates. These factors cannot be overlooked in the analysis and design of the semiconductor.Research limitations/implicationsSpecific cases are also discussed in detail, offering the potential to advance the creation of precise models and facilitate future simulations.Practical implicationsThe research offers valuable information on the physical field distribution across various temperatures, allowing engineers and designers to optimize the design of semiconductor devices. Understanding the impact of memory effect, time, conductive temperature and spatial coordinates enables device performance and efficiency improvement.Originality/valueThis manuscript is the result of the joint efforts of the authors, who independently initiated and contributed equally to this study.

Interfacial charge transfer of MoS2/ZnO/Ag2S nanotube array for efficient photocatalytic performance

Nanotubes are unique structures capable of producing light diffraction on their inner wall, amplifying curvature effect, and enhancing light excitation. These characteristics are of paramount importance in the fields of the optoelectronic and photocatalytic materials. In this study, MoS2 and its heterogeneous nanotube arrays were synthesized on FTO substrates in a vertical alignment. The hollow structure of these nanotube arrays was found to significantly enhance light absorption efficiency. The core–shell MoS2/ZnO resulted in strong electric interaction at the interface, leading to a reduced bandgap in MoS2. Being catalysts for the degradation of dye molecules, all the nanotube arrays achieved larger photocatalytic efficiency than that of the nanowire arrays with identical components. The ternary MoS2/ZnO/Ag2S array owned the best catalytic performance for the degradation of methylene blue, with efficiencies of 68.9 % and 78.1 % in 30 min under visible and UV light, respectively. Both experimental and theoretical analyses revealed the presence of a built-in electric field at the interface, directing from MoS2 to ZnO. This induced a type-II band alignment that promoted photocatalytic performance. This study highlights the exceptional optoelectronic conversion properties and photocatalytic activity of nanotube heterojunctions, holding significant implications for the design of semiconductor devices.

Comprehensive measurement of the near-infrared refractive index of GaAs at cryogenic temperatures.

The refractive index is a critical parameter in optical and photonic device design. However, due to the lack of available data, precise designs of devices working in low temperatures are still frequently limited. In this work, we have built a homemade spectroscopic ellipsometer (SE) and measured the refractive index of GaAs at a matrix of temperatures (4 K < T < 295 K) and photon wavelengths (700 nm < λ < 1000 nm) with a system error of ∼0.04. We verified the credibility of the SE results by comparing them with afore-reported data at room temperature and with higher precision values measured by vertical GaAs cavity at cryogenic temperatures. This work makes up for the lack of the near-infrared refractive index of GaAs at cryogenic temperatures and provides accurate reference data for semiconductor device design and fabrication.

A Novel Non-Invasive Cryostatic Spectrometry Technique to Characterize the Carriers’ Multiplication Factor in Silicon Carbide Power Devices

The design of robust power semiconductor devices and the assessment of their susceptibility to terrestrial cosmic rays induced failures requires the accurate characterization of the device-internal electric field. This work presents a non-invasive cryostatic spectrometry technique making use of a soft-gamma Am241 radioactive source, to sense the device-internal electric field of silicon carbide power devices, through the measurement of the carriers’ multiplication factor. TCAD and Monte Carlo simulations tools are coupled to predict the soft-gamma irradiation spectra and to localize the hotspots for charge multiplication in the device structure. An empirical relationship is derived to convert the carriers’ multiplication factor measured at cryogenic temperature to the multiplication factor at ambient temperature. Finally, by highlighting the correlation between the multiplication factor and the failure rate of power devices exposed to terrestrial cosmic radiation, the technique is proposed as a complimentary method for the on-field assessment of the Safe-Operating Area.

Optimized dopant imaging for GaN by a scanning electron microscopy.

Two-dimensional dopant profiling is vital for the modelling, design, diagnosis and performance improvement of semiconductor devices and related research and development. Scanning electron microscopy (SEM) has shown great potential for dopant profiling. In this study, the effects of secondary electron (SE) detectors and imaging parameters on the contrast imaging of multilayered p-n and p-i junction GaN specimens via SEM were studied to enable dopant profiling. The doping contrast of the image captured by the in-lens detector was superior to that of the image captured by the side-attached Everhart-Thornley detector at lower acceleration voltages (Vacc ) and small working distances (WD). Furthermore, the doping contrast levels of the in-lens detector-obtained image under different combinations of Vacc and WD were studied, and the underlying mechanism was explored according to local external fields and the refraction effect. The difference in the angular distributions of SEs emitted from different regions, the response of the three types of SEs to detectors, and the solid angles of detectors toward the specimen surface considerably influenced the results. This systematic study will enable the full exploitation of SEM for accurate dopant profiling, improve the analysis of the doping contrast mechanism, and further improve doping contrast for semiconductors.

A Quantum-Computing-Based Method for Solving Quantum Confinement Problem in Semiconductor

Technology computer-aided design (TCAD) of semiconductor devices relies on the numerical solution of differential equations in devices. Recent advances in quantum computing provide a new opportunity for TCAD simulations to be performed on a quantum computer. Based on a variational quantum algorithm, we develop a quantum-computing-based method to solve quantum confinement problems in semiconductor nanostructures. As the number of numerical discretization grid points for solving the Schrödinger equation increases, the number of qubits needed scales only logarithmically, ~ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${O}[\log(N)]$ </tex-math></inline-formula> . The method is applied to solve quantum confinement problems at all dimensions, which are related to confinement in a quantum well, semiconductor nanowire, and semiconductor quantum dot structures. The method can treat an anisotropic band structure and electrostatic potential in semiconductor nanostructures. We further show that the design of ansatz plays an important role in the performance of the method in terms of solution accuracy. The quantum-computing-based method can compute the energies and wave functions of both the ground and excited states with high accuracy.

ID Asks/Kenneth Werner

ID Asks/Kenneth Werner

Bio-inspired artificial synaptic transistors: evolution from innovative basic units to system integration.

The investigation of transistor-based artificial synapses in bioinspired information processing is undergoing booming exploration, and is the stable building block for brain-like computing. Given that the storage and computing separation architecture of von Neumann construction is not conducive to the current explosive information processing, it is critical to accelerate the connection between hardware systems and software simulations of intelligent synapses. So far, various works based on a transistor-based synaptic system successfully simulated functions similar to biological nerves in the human brain. However, the influence of the semiconductor and the device structural design on synaptic properties is still poorly linked. This review concretely emphasizes the recent advances in the novel structure design of semiconductor materials and devices used in synaptic transistors, not only from a single multifunction synaptic device but also to system application with various connected routes and related working mechanisms. Finally, crises and opportunities in transistor-based synaptic interconnection are discussed and predicted.

Dual transmission channels at metal-MoS2/WSe2 hetero-bilayer interfaces.

van der Waals heterostructures (vdWHs) open the possibility of creating novel semiconductor materials at the atomic scale that demonstrate totally new physics and enable unique functionalities, and have therefore attracted great interest in the fields of advanced electronic and optoelectronic devices. However, the interactions between metals and vdWHs semiconductors require further investigation as they directly affect or limit the advancement of high-performance electronic devices. Here we study the contact behavior of MoS2/WSe2 vdWHs in contact with a series of bulk metals using ab initio electronic structure calculations and quantum transport simulations. Our study shows that dual transmission paths for electrons and holes exist at the metal-MoS2/WSe2 hetero-bilayer interfaces. In addition, the metal-induced bandgap state (MIGS) of the original monolayer disappears due to the creation of the heterolayer, which weakens the Fermi level pinning (FLP) effect. We also find that the creation of the heterolayer causes a change in the Schottky barrier height (SBH) of the non-ohmic contact systems, whilst this does not occur so easily in the ohmic contact systems. In addition, our results indicate that when Al, Ag and Au are in contact with a MoS2/WSe2 hetero-bilayer semiconductor, a low contact barrier exists throughout the whole transmission process causing the charge to tunnel to the MoS2 layer, irrespective of whether the MoS2 is in contact with the metals as the nearest layer or as the next-nearest layer. Our work not only offers new insights into electrical contact issues between metals and hetero-bilayer semiconductors, but also provides guidance for the design of high-performance vdWHs semiconductor devices.

The effect of Bi doping on the thermal conductivity of ZnO and ZnO:Al thin films

The dissipation of heat generation has been one of the largest obstacles in the design of semiconductor devices and reducing the thermal conductivity is vital for improving thermoelectric efficiency. This work focuses on the Bi doping effect on ZnO, and ZnO:Al thin films produced by magnetron sputtering with thickness varying between 500 and 900 nm. The approach introduces Bi ions, a higher mass element, into the ZnO metal-oxide matrix, to hinder phonon-mediated heat conduction and, consequently, reduce thermal conductivity. Atom probe tomography (APT) was employed to survey Bi doping distribution in ZnO:Al:Bi and ZnO:Bi thin films and to study the morphology of the grain boundaries. The thermal properties of the thin films were measured by frequency-domain thermoreflectance. Based on thermal conductivity results, it is concluded that the doping of ZnO films with Al has a significant effect on thermal conductivity, being reduced from 6.0 W m−1 K−1 in its undoped state to 3.3 W m−1 K−1 for ZnO with ∼3 at.% of Al, mainly due to alloy scattering of phonons in the wurtzite cell. Further doping with Bi contributes to a slight reduction in the thermal conductivity of ZnO:Al.Bi films (2.9 W m−1 K−1), due to grain boundary scattering by Bi/Bi2O3 phases. This result is understood as the confluence of two counteracting effects. On the one hand, the thermal conductivity of the film decreases because Bi, unlike Al, is segregated to grain boundaries and does not substitute Zn in the wurtzite crystal lattice, which is unequivocally demonstrated by APT results. On the other hand, the simultaneous presence of Al and Bi triggers a morphological change with the film's microstructure becoming more columnar. This change in microstructure from 3D island growth in ZnO:Al and ZnO:Bi to a more regular columnar structure in ZnO:Al,Bi limits further reduction in the thermal conductivity.

Deriving the absorption coefficients of lattice mismatched InGaAs using genetic algorithm

Lattice-mismatched InGaAs has appeared to be emerging semiconductor materials for sensors and photovoltaic applications. The absorption coefficients of the materials are crucial in designing high-performance semiconductor devices. Nevertheless, the absorption coefficient of lattice-mismatched InGaAs were not comprehensively studied to cater for the 2000–3000 nm applications. This study aims to determine the absorption coefficients of lattice-mismatched In0.73Ga0.27As and In0.83Ga0.17As semiconductor materials through photocurrent measurement which enables the absorption tail information to be extracted. In addition, this work demonstrates the incorporation of an innovative artificial intelligence-based method in solving the absorption coefficient of lattice-mismatched InGaAs, considering the detailed information of the structure design and material parameters. By selecting the best gene for the next iteration, the utilization of Genetic Algorithm has significantly reduced the number of iterations from a maximum of 10 000 to 300. Validation of the algorithm was conducted, showing a good agreement of absorption coefficient result compared to the published work on In0.72Ga0.28As. The absorption coefficient of In0.83Ga0.17As with an extended cutoff wavelength near 2.6 μm is newly reported in this paper. In addition, the extrapolation of the obtained absorption results demonstrates energy gaps of 0.475 eV for In0.73Ga0.27As and 0.55 eV for In0.83Ga0.17As, which are compatible with the reported bandgaps of these materials. The extracted absorption coefficient information can be used in the design of semiconductor devices for emerging technologies such as focal plane array, short wave infrared sensing and thermophotovoltaic.

Characterization of the carriers' multiplication in Si and SiC power devices by soft-gamma irradiation under cryostatic conditions

The characterization of the carriers' multiplication factor is a key issue for the design of robust and reliable power semiconductor devices and for the assessment of their susceptibility to terrestrial cosmic radiation induced failures. A cryostatic setup is presented to extend the applicability of non-invasive charge spectroscopy techniques using soft-gamma radiation from an Am241 radioactive source to a broad class of Si and SiC devices. A relationship is provided to convert the multiplication factor measured at liquid nitrogen temperature to the multiplication measured at ambient temperature. A dedicated simulation scheme is proposed that couples TCAD and Monte Carlo tools to predict the spectra of the collected charge and to locate hotspots of the multiplication factor. Finally, after highlighting the correlation between the charge multiplication factor and the failure rate of power devices submitted to terrestrial cosmic radiation, the present technique is suggested as a complementary method to assess the Safe-Operating Area.