Materials For Semiconductor Devices Research Articles

In Situ transmission Electron Microscope Observation of Biased-Induced Dynamic Evolution of Two-Dimensional CrS2

Two-Dimensional transition-metal dichalcogenides (2D-TMDs) have attracted great attention recently owing to their potential to become the important material for next generation semiconductor devices. While using the device, it needs to ensure high density current and biased voltage for a long time. However, the study on TMDs in high-energy environment is insufficient. In this work, the phase evolution of CrS2 are revealed via in-situ biasing experiments and recorded by transmission electron microscope (TEM) at atomic scale. The ultra-thin layered (~1.6nm) CrS2 was synthesized through atmospheric pressure chemical vapor deposition (APCVD), followed by transferring the as-grown samples onto specialized TEM electrical chips. The TEM characterization of CrS2 initial sample provided the basic understanding of this Cr-based TMD, identified as pure 1T phase with single crystal structure as shown in Figure 1. The advanced in situ technique was employed to record the structural evolution and was tested the endurance of CrS2 during biasing. Moreover, the results can make significant contributions to future semiconductor device designs and demonstrate CrS2 has great potential as a semiconductor device with its outstanding characteristic of biased-endurance. Figure1. (a) Low-magnification TEM image of 1T-CrS2. (b) High-resolution TEM image of 1T-CrS2, corresponding with FFT along [001] zone axis. (c) AFM image of the as-grown CrS2 sample, blue bar in the image is X axis of (d). (d) AFM height profile of as-grown 1T-CrS2 with average thickness of~1.6nm. (e) STEM image of 1T-CrS2 and shows d-spacing~0.336 nm. (f) Low-magnification TEM image of the device, showing that the transferred CrS2 layer was suspended on the membrane with Au electrodes on both sides. (g,h) In-situ TEM observation of the biasing experiment after 5V biasing for 5 min of 1T-CrS2. Time-sequencing TEM images showing the structural evolution of biasing. The inset shows the corresponding FFT-DP to reveal the variation of crystallinity of the sample. (g) Initial structure of 1T-CrS2. (h) 1T-CrS2 under in-situ biasing experiment after 10 minutes. Figure 1

Asymmetrical impurity effect of C70:C60 mixture in thick small molecule organic photovoltaic cells

Fullerenes, especially C70 and C60, and their derivatives are popular acceptor materials for many organic semiconductor devices, including organic photovoltaic cells. One of the main impurities in C70 is C60, and intentional mixture of C60 and C70, or their derivatives, which have been utilized for maximizing the performance of organic photovoltaic cells or perovskite solar cells. However, the influence of impurities in C70 on the device characteristics has not been fully clarified when incorporating C70 into organic devices. To further clarify the relationship between the fullerene mixture and impurities, the effect of impurities in fullerenes on thick photovoltaic cells was evaluated, and a strange asymmetrical impurity effect of the C60:C70 mixture was demonstrated by using C70 with various purities as an acceptor material and zinc phthalocyanine (ZnPc) as a donor material. It was found that C60, C78, and C84 impurities in C70 caused carrier recombination during electron transport, but the same effect of the C70 impurity in C60 was much smaller. Additionally, the impurity effect of higher fullerenes on C70 was clearly larger than that of C60. The effect of higher fullerene impurities can be explained by electron trapping due to their deep lowest unoccupied molecular orbital (LUMO) levels. For the small difference of LUMO energy between C70 and C60, however, it is suggested that the shallow trapping of C70 impurities does not largely inhibit the transport of photocarriers by C60, while the low energy barrier of C60 impurities largely inhibits the transport of photocarriers by C70. For clear comparison, the photoelectrical conversion layers were crystallized using co-evaporant induced crystallization. An effective purification method for C70 using sublimation purification, which depends on the C70 concentration in the sublimation source, is also reported.

Area-selective deposition of germanium on patterned graphene/monolayer molybdenum disulfide stacks via dipole engineering

Heterogeneous integration of two-dimensional materials and the conventional semiconductor has opened opportunities for next-generation semiconductor devices and their processing. Heterogeneous integration has been studied for economical manufacturing by substrate recycling and novel functionalities by a combination of incommensurate materials. However, utilizing the integration requires controlling locations of the integrated architectures. Here, we show area-selective deposition (ASD) of germanium on the graphene/MoS2 stack. Ge nucleation precisely occurred on the surfaces of the patterned graphene/MoS2 stack via dipole engineering. In this study, the growth temperature of ASD of Ge was significantly lower than that based on precursor desorption on SiO2. The first-principles calculations revealed that Ge deposited by ASD on the graphene/MoS2 stack was not affected by charge transfer. This work provides a viable way to utilize atomically thin materials for next-generation semiconductor devices, which can be applicable for “Beyond Moore” and “More Moore” approaches.

Rapid microwave-assisted synthesis and characterization of a novel CuCoTe nanocomposite material for optoelectronic and dielectric applications.

In the realm of nanomaterial research, copper telluride and cobalt telluride have individually attracted considerable attention owing to their unique properties and potential applications. However, there exists a notable gap in the literature when it comes to the exploration of composite materials derived from these elements. From this point of view, a ternary CuCoTe nanocomposite was prepared using the microwave synthesis method. Various characterizations were performed by varying the power and irradiation time. X-Ray diffraction study and transmission electron microscopy analysis confirmed the polycrystalline nature of the material with Cu2Te and CoTe hexagonal phases. Field emission scanning electron microscopy images reveal nanoparticle-like morphology, which remains unchanged even when the time of irradiation increases. In addition, the nanoparticle size of the material lies in the range of 30-39 nm. The differential scanning calorimetry inferred various exothermic and endothermic peaks. Meanwhile, the optical analysis from the UV-visible study shows the red-shifted absorbance, enabling the material for semiconductor and photovoltaic devices. Furthermore, the optical bandgap of the material varies in the range from 2.45 to 3.61 eV, which reveals the tuneable bandgap desiring the material for various optoelectronic applications. The frequency-temperature-dependent dielectric study gives results for dielectric parameters, conductivity, and impedance behaviour. The material's dielectric constant, dielectric loss, and AC conductivity enhance with the increase in temperature. This behaviour of the material broadens the area of applicability in energy storage devices.

Band gap engineering in lead free halide cubic perovskites GaGeX3 (X = Cl, Br, and I) based on first-principles calculations.

Lead-free inorganic Ge-based perovskites GaGeX3 (X = Cl, Br, and I) are promising candidates for solar cell applications due to their structural, mechanical, electrical, and optical properties. In this work, we performed density functional theory (DFT) calculations using the CASTEP module to investigate these properties in detail. We found that the lattice parameters and cell volumes increase with the size of the halogen atoms, and that all the compounds are stable and ductile. GaGeBr3 has the highest ductility, machinability, and lowest hardness, while GaGeCl3 has the highest anisotropy. The band gap values, calculated using the GGA-PBE and HSE06 functionals, show a direct band gap at the R-R point, ranging from 0.779 eV and 1.632 eV for GaGeCl3 to 0.330 eV and 1.140 eV for GaGeI3. The optical properties, such as absorption coefficient, conductivity, reflectivity, refractive index, extinction coefficient, and dielectric function, are also computed and discussed. We observed that the optical properties improve with the redshift of the band gap as Cl is replaced by Br and I. GaGeI3 has the highest dielectric constant, indicating the lowest recombination rate of electron-hole pairs. Our results suggest that GaGeX3 (X = Cl, Br, and I) can be used as effective and non-toxic materials for multijunction solar cells and other semiconductor devices.

Rapid grinding diamond film using a grinding wheel containing nickel-plated diamond abrasives based on mechanochemical effect

The excellent properties of diamond make it a highly promising substrate material for future sensors and semiconductor devices. The surface roughness of the substrate material directly impacts the performance of the devices. Therefore, achieving efficient and low-damage processing of diamonds is crucial. However, diamond has high hardness and chemical inertness, which makes it difficult to process. To tackle the above-mentioned problem, the diamond film was ground using a grinding wheel containing nickel (Ni)-plated diamond abrasives based on the mechanochemical effect. The maximum average material removal rate of the diamond film reached 2469 nm/min under a grinding pressure of 600 N at a speed of 600 rpm, and the minimum average surface roughness of the diamond film reached 3.93 nm under 500 N 600 rpm. The rapid reaction removal of the diamond film can be attributed to the catalytic effect of the Ni plating, inducing graphitization of the diamond film at the interface contact points under the generated high temperature during friction; subsequently, it can be removed under the mechanical action of the abrasives. This work has tremendous potential for the efficient and low-damage grinding of diamond films.

Photo-Enhanced Inverse Metal-Assisted Chemical Etching of α-Ga2O3 grown on Al2O3

Si-based semiconductor devices are not suitable for stable operations in the aerospace environments. Among the ultra-wide bandgap semiconductor materials, gallium oxide (Ga2O3) is attracting attention as the next-generation material for high-power semiconductor devices in extreme condition beyond Si, owing to its large band gap of 4.5-5.3 eV, high breakdown electric fields of 7-10 MV/cm, excellent chemical and thermal stability and radiation hardness. Alpha gallium oxide (α-Ga2O3) has the largest bandgap (4.8-5.3 eV) and the highest breakdown electric fields (~10 MV/cm) among the five Ga2O3 polymorphs, which facilitates the application of α-Ga2O3 as a high power device. However, the research on etching technology for α-Ga2O3 is rare. Etching technology is a crucial step of device fabrication. Chemical etching is free from plasma-induced damage which leads to superior device performance compared with dry etching, and high throughput with low cost is beneficial to industrial implementations. Chemical stability of Ga2O3 hinders the effective reaction with most chemical etchants. However, the photo-enhanced inverse metal assisted chemical (I-MAC) etching, where a noble metal with a high work function is utilized as a catalyst under UV irradiation, has emerged as a candidate for the chemical etching of Ga2O3. Deep-UV irradiation generates electron-hole pairs (EHPs) in the uncovered region of Ga2O3, and the metal electrode withdraws carriers from the photo-generated EHPs. The holes that are accumulated in the uncovered region of Ga2O3 react with gallium ions which produce gallium fluoride (GaF3) in a reaction with Hydrofluoric acid (HF). The etching process continues as the oxidant re-oxidizes the metal. The etch rate can be controlled by various parameter, including concentration and temperature of the etchant. In this work, for the I-MAC etch of α-Ga2O3 on sapphire substrate grown by halide vapor phase epitaxy, Pt was deposited on α-Ga2O3. Etch rate and surface roughness were characterized by atomic force microscopy after each step of the I-MAC etch. The I-MAC etch using HF and potassium persulfate (K2S2O8) solution with 185-nm UV irradiation was performed at constant durations under different etchant temperature conditions. The etch rates obtained at each temperature condition were fitted with the Arrhenius plot to estimate the activation energy of 0.898 eV. The etch depth showed a linear increase with time and the etch rate exhibits a direct dependency on the temperature of the etchant, indicating that the I-MAC etching of α-Ga2O3 is an activation-controlled reaction. As the I-MAC etching proceeded, surface roughness of α-Ga2O3 showed a tendency to increase. The rate at which the surface roughness increased increased with raising the etchant temperature. In the case of Pt there was no significant difference in the surface roughness after etching. After the completion of the I-MAC etch, the remaining Pt can be removed using aqua regia. The I-MAC etch process of α-Ga2O3 can allow us to fabricate α-Ga2O3 without plasma-damage. Figure 1

Adsorption on 3C-SiC surfaces in chemical vapor deposition process of CH3SiCl3–H2 system: a first-principles study

SiC has become increasingly important in high-energy semiconductor device materials and structural composite materials in recent years. Many systematic experimental studies have been conducted on the preparation of cubic silicon carbide (3C-SiC) by the chemical vapor deposition (CVD) process. Despite this, the microscopic mechanism of the SiC deposition process has not been fully elucidated due to the limitations of the experimental methods. Based on these problems, the structural parameters, adsorption energies, charge populations, transition states, and electronic densities of states of Si-Cl-C-H at different sites were simulated by a first-principles method, and the micro-mechanism of the surface deposition reaction was analyzed. The calculated results provide a theoretical and experimental basis for the study of 3C-SiC preparation by CVD.

Investigation of semiconductor properties of Co/Si(111)-7 × 7 by AFM/KPFS

Studies of the physics underlying carrier transport characteristics and band bending of semiconductors are critical for developing new types of devices. In this work, we investigated the physical properties of Co ring-like cluster (RC) reconstruction with a low Co coverage on a Si(111)-7 × 7 surface at atomic resolution by atomic force microscopy/Kelvin probe force microscopy at 78 K. We compared the applied bias dependence of frequency shift between two types of structure: Si(111)-7 × 7 and Co-RC reconstructions. As a result, the accumulation, depletion, and reversion layers were identified in the Co-RC reconstruction by bias spectroscopy. For the first time, we found that Co-RC reconstruction on the Si(111)-7 × 7 surface shows semiconductor properties by Kelvin probe force spectroscopy. The findings of this study are useful for developing new materials for semiconductor devices.

A comprehensive study of defects in gallium oxide by density functional theory

Ultrawide bandgap gallium oxide (Ga2O3) is a promising material for power semiconductor devices and deep ultraviolet (UV) solar-blind photodetectors. Understanding the properties of point defects in Ga2O3 is necessary to realize better-performing devices. A comprehensive study based on density functional theory (DFT), using the generalized gradient approximation (GGA): Perdew-Burke-Ernzerhof (PBE) exchange–correlation functional, of point defects in corundum (α), monoclinic (β), and orthorhombic (ε) phases of Ga2O3 is presented. The point defects include vacancies, interstitials, antisites, and extrinsic impurities in various phases of Ga2O3. Defect formation energies, charge transition energy levels, and defect concentrations variation with temperature are listed and presented under both gallium-rich (Ga-rich) and oxygen-rich (O-rich) growth conditions. The formation energy diagrams predict that the Ga2O3 phases favor the formation of Ga and O vacancies and the incorporation of extrinsic impurities. The calculations also show that the charge transition levels are deep inside the bandgap regardless of the Ga2O3 phase and growth environment. The impacts of temperature on the intrinsic point defects are analyzed by probing the vibrational modes of β-Ga2O3 thin films grown in a metal–organic chemical vapor deposition (MOCVD) system at 700 °C temperature and annealed at 1100 °C in an O-rich environment.

Nanometer-Thick Oxide Semiconductor Transistor with Ultra-High Drain Current.

High drive current is a critical performance parameter in semiconductor devices for high-speed, low-power logic applications or high-efficiency, high-power, high-speed radio frequency (RF) analogue applications. In this work, we demonstrate an In2O3 transistor grown by atomic layer deposition (ALD) at back-end-of-line (BEOL) compatible temperatures with a record high drain current in planar FET, exceeding 10 A/mm, the performance of which is 2-3 times better than all known transistors with semiconductor channels. A high transconductance reaches 4 S/mm, recorded among all transistors with a planar structure. Planar FETs working ballistically or quasi-ballistically are exploited as one of the simplest platforms to investigate the intrinsic transport properties. It is found experimentally and theoretically that a high carrier density and high electron velocity both contribute to this high on-state performance in ALD In2O3 transistors, which is made possible by the high-quality oxide/oxide interface, the metal-like charge-neutrality-level (CNL) alignment, and the high band velocities induced by the low density-of-state (DOS). Experimental Hall, I-V, and split C-V measurements at room temperature confirm a high carrier density of up to 6-7 × 1013 /cm2 and a high velocity of about 107 cm/s, well-supported by density functional theory (DFT) calculations. The simultaneous demonstration of such high carrier concentration and average band velocity is enabled by the exploitation of the ultrafast pulse scheme and heat dissipation engineering.

Suppression of stacking-fault expansion in 4H-SiC PiN diodes using proton implantation to solve bipolar degradation

4H-SiC has been commercialized as a material for power semiconductor devices. However, the long-term reliability of 4H-SiC devices is a barrier to their widespread application, and the most important reliability issue in 4H-SiC devices is bipolar degradation. This degradation is caused by the expansion of single Shockley stacking-faults (1SSFs) from basal plane dislocations in the 4H-SiC crystal. Here, we present a method for suppressing the 1SSF expansion by proton implantation on a 4H-SiC epitaxial wafer. PiN diodes fabricated on a proton-implanted wafer show current–voltage characteristics similar to those of PiN diodes without proton implantation. In contrast, the expansion of 1SSFs is effectively suppressed in PiN diodes with proton implantation. Therefore, proton implantation into 4H-SiC epitaxial wafers is an effective method for suppressing bipolar degradation in 4H-SiC power-semiconductor devices while maintaining device performance. This result contributes to the development of highly reliable 4H-SiC devices.

Failure analysis on silicon semiconductor device materials: optical and high-resolution microscopic assessments

Defects of silicon (Si) semiconductor epilayers are crucial to be identified at laboratory environs. The identification of failure and its rectification at laboratory settings is essential for large-scaling manufacturing of narrowed down semiconductor devices. This research documented the inspection, identification and the solution for defects found in the Si semiconductor epilayers, fabricated by a simple and conventional photolithography technique, with the integration of metal oxide nanomaterial, zinc oxide (ZnO). The semiconductor epilayers, Si wafer, Si oxide and ZnO coated SiO2 layer were formed and examined. Optical microscope images [high power microscope (HPM) and 3D profilometer] reveal smooth surface of semiconductor epilayers development through thermal oxidation and photolithography techniques. High power ultraviolet-visible (UV-Vis) justified the accuracy of wet thermal oxidation by examining the thickness of oxide layer on Si wafer at 3837.3 Å. The X-ray diffraction (XRD) analysis of sol-gel synthesized ZnO affirmed the hexagonal crystalline state and its nanoscale size at 54 nm. Field emission scanning electron microscopy (FESEM) has shown the insight of Si epilayer morphology with its elemental composition, which provides details of foreign substances on semiconductor surface. ZnO deposited Si epilayer was prepared through lamella preparation, prior to the cross-sectional field emission transmission electron microscopy (FETEM) analysis of the semiconductor, which revealed the uniformity of fabrication and ZnO distribution at Si epilayer. Failure analysis reported several defects on the Si epilayers in the state of patches and accumulation of impurities. The potential cause of the defects and the respective solutions are discussed as the accuracy and handling must be ensured throughout the fabrication process, to develop a flawless semiconductor for high performance applications.

(Invited) Deep Level Defects in AlN Studied By UV-Visible Spectroscopy

The ultrawide-bandgap (UWBG) AlGaN alloy system is emerging as a promising material for next generation power semiconductor devices. The increase in bandgap as the alloy composition is varied from the binary endpoints GaN to AlN leads to an increase in the critical electric field, which is a key parameter determining the performance of power semiconductor devices. As development of GaN and SiC materials for high-frequency and high-power devices reaches a state of maturity, pursuit of improved device performance is generating interest in UWBG materials with larger bandgaps. High Al composition AlGaN alloys, in addition to offering increased critical electric fields, offer prospects for improved device performance in high temperature operation. Fundamental challenges to the development of AlGaN-based devices, such as controllable doping, electrical contacts, and effective passivation, remain, but a variety of power devices have already been demonstrated (1-3).Point defects strongly affect the material properties of semiconductors, with important consequences for device performance. In traditional semiconductors, such as Si, point defects have been studied extensively, and point defect engineering methods have been developed to enhance device performance. However, the properties of point defects in UWBG materials are not as well understood. Point defects may be introduced during device growth, fabrication, and operation. On the one hand, intentionally introduced impurities (dopants) are critical to the control of electrical transport, while on the other hand, unintentionally introduced impurities may act deleteriously as carrier traps or recombination centers. In AlGaN, compensation by deep level, native point defects or unintentionally incorporated impurities limits achievable free carrier concentrations in electronic devices, while defects and their complexes affect the optical properties in optoelectronic devices. Since point defects exert such a strong influence on material properties, and are often responsible for device degradation, knowledge of their formation mechanisms and material effects are essential to develop strategies for the required control of point defect concentrations (4).In this work, we studied the optical signatures of deep level defects in single crystal AlN substrates. AlN possesses a high thermal conductivity and a close lattice match to high Al composition alloys, which make it an excellent substrate choice for growth of AlGaN-based power electronic and optoelectronic devices. High-quality, 2-inch diameter AlN substrates with average threading dislocation densities below 103 cm-2 were recently demonstrated (5). However, high optical absorption in the ultraviolet-C (UV-C) region was observed in AlN substrates grown by physical vapor transport (PVT), due to a deep level absorption band related to the carbon impurity. This absorption band negatively impacts the efficiency of UV-C optoelectronic devices that require light propagation through the substrate. In order to reduce the unwanted UV-C absorption, we studied the optical properties of double-side polished, 2-inch, c-plane AlN substrates by ultraviolet-visible (UV-Vis) spectroscopy and developed strategies for point defect control. Spatially uniform absorption coefficients below 30 cm-1 at 265 nm were demonstrated across 2-inch substrates (6). In this talk, UV-Vis absorption, photoluminescence (PL) emission, and PL excitation spectra will be presented and correlated with measured impurity concentrations from secondary ion mass spectrometry (SIMS) data, in order to identify deep level defects in AlN. Finally, the mechanisms for reduction of UV-C absorption in PVT AlN will be discussed.References R. J. Kaplar, A. A. Allerman, A. M. Armstrong, M. H. Crawford, J. R. Dickerson, A. J. Fischer, A. G. Baca, and E. A. Douglas, ECS J. Sol. State Sci. and Technol. 6(2), Q3061 (2017).P. H. Carey IV, F. Ren, A. G. Baca, B. A. Klein, A. A. Allerman, A. M. Armstrong, E. A. Douglas, R. J. Kaplar, P. G. Kotula, and S. J. Pearton, IEEE Trans. Semicond. Manuf. 32(4), 473 (2019).A. G. Baca, A. M. Armstrong, B. A. Klein, A. A. Allerman, E. A. Douglas, and R. J. Kaplar, J. Vac. Sci. Technol. A 38, 20803 (2020).S. Washiyama, P. Reddy, B. Sarkar, M. H. Breckenridge, Q. Guo, P. Bagheri, A. Klump, R. Kirste, J. Tweedie, S. Mita, Z. Sitar, and R. Collazo, J. Appl. Phys. 127, 105702 (2020).R. Dalmau, J. Britt, H. Fang, B. Raghothamachar, M. Dudley, and R. Schlesser, Mater Sci. Forum 1004, 63 (2020).R. Dalmau, S. Kirby, J. Britt, and R. Schlesser, ECS Trans. 104(7), 49 (2021).

Ion-gating analysis on conduction mechanisms in oxide semiconductors

• Self-gated field-effect by ion adsorption at the solid–liquid interface (ion-gating). • Resistive factors of indium tin oxide controlled depending on sputtering conditions. • A fundamental correlation between the ion-gating effect and the resistive factors. • Ion-gating analysis on the resistance-dependent behavior of electrons in the electrode. • Identification of conduction mechanisms in amorphous oxide semiconductors. The electric field-effect is one of the common methods to tune the conductivity of materials in semiconductor devices because it can control the accumulation or depletion of charge carriers. However, to efficaciously dominate the electrical properties of the semiconductor in such a way, the application of an external voltage through the gate is an inevitable condition. Here, we propose an ion-dynamics-driven (ionovoltaic) transducer focusing on a self-gated field-effect by ion adsorption at the solid–liquid interface (an ion-gating effect without applied electric field). Considering an effective resistance derived from the generated signal, we establish an equivalent circuit of the ion-gating field-effect transducer to specifically analyze the conduction behavior of traveling electrons in an amorphous indium tin oxide film. As a result, using water droplet flow, we provide a convenient method to identify inherent conduction mechanisms of amorphous oxide semiconductors. This analysis has great potential as a tool to leap forward into a new interdisciplinary approach covering interface science and solid-state physics from a peculiar concept based on the ion-gating effect.

Two-dimensional germanene-based Janus material Ge8HnX8−n (n = 0–8, X = F, Cl, Br, I) for photovoltaic and photocatalytic applications

The high-throughput calculation of two-dimensional (2D) materials can provide new candidate materials for semiconductor devices in many new structures, optimize their electrical properties, and break through the performance bottleneck of original devices. The surface functionalization of the germanene structure significantly affects its stability and photoelectric properties. However, due to the diversity and complexity, the design of a potential new Janus germanene-based structure will necessitate costly computational resources and a lengthy research period. In this paper, a framework of the classification algorithm (random forests classification), regression algorithm (ridge regression and support vector regression), and fitting method was established using a combination of machine learning and density functional theory. Using our designed framework, the stability (binding energy) and electrical properties (band gap, valence band maximum) of 2D germanene-based structures Ge8HnX8−n (n = 0–8, X = F, Cl, Br, and I) can be predicted effectively by 33 simple features. In unexplored germanene-based structures, we successfully designed ten novel single structures and three new heterojunctions with potential photovoltaic or photocatalytic applications by the designed framework and density functional theory verification, in which Ge8H6ClBr/Ge8H5Br2I has a high photoelectric conversion efficiency of 23.24%.

Reduction of parasitic reaction in high-temperature AlN growth by jet stream gas flow metal–organic vapor phase epitaxy

AlGaN-based deep ultraviolet light-emitting diodes (LEDs) have a wide range of applications such as medical diagnostics, gas sensing, and water sterilization. Metal–organic vapor phase epitaxy (MOVPE) method is used for the growth of all-in-one structures, including doped layer and thin multilayers, using metal–organic and gas source raw materials for semiconductor devices. For AlN growth with high crystalline quality, high temperature is necessary to promote the surface migration of Al atoms and Al-free radicals. However, increase in temperature generates parasitic gas-phase prereactions such as adduct formation. In this work, AlN growth at 1500 °C by a stable vapor phase reaction has been achieved by jet stream gas flow metal–organic vapor phase epitaxy. The AlN growth rate increases with gas flow velocity and saturates at ~ 10 m/s at room temperature. Moreover, it is constant at an ammonia flow rate at a V/III ratio from 50 to 220. These results demonstrate the reduction in adduct formation, which is a typical issue with the vapor phase reaction between triethylaluminum and ammonia. The developed method provides the in-plane uniformity of AlN thickness within 5%, a low concentration of unintentionally doped impurities, smooth surface, and decrease in dislocation density because of the suppression of parasitic reactions.

Thermal stability of electrical parameters of silicon crystal doped with nickel during growth

This work shows that the introduction of nickel atoms in the process of growing silicon crystals enables to obtain a material with stable electrophysical parameters during thermal annealing in the wide temperature range 450…1050 °С and duration (t = 0.5...25 hours). This is the most cost-effective way to create material for semiconductor devices and solar cells with stable parameters.

Properties and Applications of Copper(I) Thiocyanate Hole‐Transport Interlayers Processed from Different Solvents

AbstractCopper(I) thiocyanate (CuSCN) is an effective interlayer material for hole injection and transport in organic electronic devices but its solution processing has conventionally utilized undesirable di‐n‐alkyl sulfide solvents such as diethyl‐ (DES) and dipropyl‐sulfide (DPS). Herein, this paper reports on the use of N,N‐dimethylformamide (DMF) and 1‐methyl‐2‐pyrrolidinone (NMP) as alternative solvents for CuSCN interlayers and performs a detailed comparison of the resulting properties relative to films processed from DES and DPS and two other recent alternatives, dimethyl sulfoxide (DMSO) and ammonium hydroxide. The surface roughness, polymorphism, and surface chemistry of the resulting CuSCN layers are reported. The interlayer surface energy and ionization potential that are key to the overlying semiconductor microstructure and interfacial energy barrier, and hence to charge transport and injection, are also discussed. Finally, systematic device tests using well‐known organic semiconductors in light‐emitting diode, solar cell and field‐effect transistor structures demonstrate the overall suitability of DMSO and DMF as solvents for CuSCN interlayer deposition to achieve better device performance. This study broadens the applicability of CuSCN as a highly efficient hole injection/transport material for organic semiconductor devices by expanding the documented range of suitable CuSCN solvents.

Versatile perovskite and its various applications

Since their discovery in 1839, perovskite materials have played a significant role in development of low-cost energy products for photovoltaics, light emitting diodes, sensors, fuel cells, photocatalysis, and memory applications. This featured letter provides a critical overview of the recent advancements and challenges in the use of perovskite materials for semiconductor devices, with a focus on the various properties of these materials and their suitability for different applications.