Compound Semiconductors Research Articles

Tuning Interfacial Chemistry to Direct the Electrosynthesis of Metal Oxide Semiconductors.

ConspectusMetal oxide semiconductors have many features that make them attractive for both fundamental and applied studies. For example, these compounds contain elements (e.g., Fe, Cu, Ti, etc.) that are derived from minerals rendering them earth-abundant and, most often, are also not toxic. Therefore, they have been examined for possible applicability in a very diverse range of technological applications including photovoltaic solar cells, charge storage devices, displays, smart windows, touch screens, etc. The fact that metal oxide semiconductors have both n- and p-type conductivity makes them amenable for use as hetero- or homojunctions in microelectronic devices and as photoelectrodes in solar water-splitting devices. This Account presents a review of collaborative research on the electrosynthesis of metal oxides from our respective groups against the backdrop of key developments on this topic. The many variants that interfacial chemical modification schemes offer are shown herein to lead to the targeted synthesis of a wide array of not only simple binary metal oxides but also more complex chemistries involving multinary compound semiconductors and alloys.This Account presents our perspective on how parallel developments in the understanding of and ability to manipulate electrode-electrolyte interfaces have correspondingly enabled the innovation of a broad array of electrosynthetic strategies. These coupled with the advent of versatile tools to probe interfacial processes (undoubtedly, a child of the nanotechnology "revolution") afford an operando examination of how effective the strategies are to secure the targeted metal oxide product as well as the mechanistic nuances. Flow electrosynthesis, for example, removes many of the complications accruing from the accumulation of interfering side products─veritably, this is an Achilles heel of the electrosynthesis approach. Coupling flow electrosynthesis with downstream analysis tools based on spectroscopic or electroanalytical probes opens up the possibility of immediate process feedback and optimization. The combination of electrosynthesis, stripping voltammetry, and electrochemical quartz crystal nanogravimetry (EQCN), either in a static or in a dynamic (flow) platform, is shown below to offer intriguing possibilities for metal oxide electrosynthesis. While many of the examples below are based on our current and recent research and in other laboratories, unlocking even more potential will hinge on future refinements and innovations that surely are around the corner.

Material full of promises: Hg1-xCdXTe - mercury cadmium telluride

In recent decades’ doctors and scientists have intensively researched the effect of infrared applications. The rays of infrared devices penetrate the body to a depth of about 5 cm and provide a pleasant warmth, stimulating blood circulation and reducing joint pain. Long-wave infrared light exerts a beneficial effect on nerve cells. These nerve cells are responsible for transmitting the sensation of pain to the brain. Infrared light treatment increases the release of endogenous analgesic substances from the brain and adrenal glands, such as enkephalins and endorphins. The infrared range of the electromagnetic spectrum extends from about 0.75 μm to 1000 μm. The article presents a review of HgCdTe infrared detectors, which have been intensively developed in the last forty years since the first synthesis of this compound semiconductor in 1958.

High Photosensitivity Nanocrystalline p-Cu2S/n-FTO Heterojunction Photodetectors Prepared by Dip Coating Method

Objective: The aim of present work is to fabricate nanocrystalline p-Cu2S/n-FTO heterojunction photo detectors with high photosensitivity. Methods: Copper sulphide (Cu2S) is semiconductor compound belonging to I-VI group. Cost effective chemical method was used to synthesize thioglycerol capped Cu2S nanoparticles with improved optoelectronic and physical properties. These nanoparticles were investigated by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). Cu2S films were deposited on fluorine doped tin oxide (FTO) glass slides using cost effective dip coating method at different dip times and heat treated in air atmosphere. Wide band gap fluorine doped tin oxide, n-type semiconductor was used as transparent window material together with narrow band gap Cu2S, p-type semiconductor used as absorber layer in case of Cu2S/FTO heterojunction photo detectors under reverse biased mode and illumination. Results: Cu2S films were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Analysis by X-rays (EDAX), Mapping and Atomic Force Microscopy (AFM). Selected Area Electron Diffraction (SAED) images showed ring patterns indicating that Cu2S nanoparticles are polycrystalline in nature and spot patterns indicating that Cu2S nanoparticles are monocrystalline in nature. Conclusion: Previously, preparation of optoelectronic devices such as photo detectors using Cu2S films has not been reported. In this study, photo detectors having enhanced photosensitivity were prepared using Cu2S films. I-V characteristics of p-Cu2S/n-FTO heterojunctions under dark and illumination conditions were examined. It was observed that film conductivity decreases under dark condition and increases under illumination condition with increase in dip time in case of Cu2S/FTO heterojunction photo detectors.

Combining x-ray real and reciprocal space mapping techniques to explore the epitaxial growth of semiconductors

In the present work, the importance of determining the strain states of semiconductor compounds with high accuracy is demonstrated. For the matter in question, new software titled LAPAs, the acronym for LAttice PArameters is presented. The lattice parameters as well as the chemical composition of Al1−x In x N and Ge1−x Sn x compounds grown on top of GaN- and Ge- buffered c-Al2O3 and (001) oriented Si substrates, respectively, are calculated via the real space Bond’s method. The uncertainties in the lattice parameters and composition are derived, compared and discussed with the ones found via x-ray diffraction reciprocal space mapping. Broad peaks lead to increased centroid uncertainty and are found to constitute up to 99% of the total uncertainty in the lattice parameters. Refraction correction is included in the calculations and found to have an impact of 0.001 Å in the lattice parameters of both hexagonal and cubic crystallographic systems and below 0.01% in the quantification of the InN and Sn contents. Although the relaxation degrees of the nitride and tin compounds agree perfectly between the real and reciprocal-spaces methods, the uncertainty in the latter is found to be ten times higher. The impact of the findings may be substantial for the development of applications and devices as the intervals found for the lattice match the condition of Al1−x In x N grown on GaN templates vary between ∼1.8% (0.1675–0.1859) and 0.04% (0.1708–0.1712) if derived via the real- and reciprocal spaces methods.

Ultrafast electron localization and screening in a transition metal dichalcogenide

The coupling of light to electrical charge carriers in semiconductors is the foundation of many technological applications. Attosecond transient absorption spectroscopy measures simultaneously how excited electrons and the vacancies they leave behind dynamically react to the applied optical fields. In compound semiconductors, these dynamics can be probed via any of their atomic constituents with core-level transitions into valence and conduction band. Typically, the atomic species forming the compound contribute comparably to the relevant electronic properties of the material. One therefore expects to observe similar dynamics, irrespective of the choice of atomic species via which it is probed. Here, we show in the two-dimensional transition metal dichalcogenide semiconductor MoSe2, that through a selenium-based core-level transition we observe charge carriers acting independently from each other, while when probed through molybdenum, the collective, many-body motion of the carriers dominates. Such unexpectedly contrasting behavior can be explained by a strong localization of electrons around molybdenum atoms following absorption of light, which modifies the local fields acting on the carriers. We show that similar behavior in elemental titanium metal [M. Volkov et al., Nat. Phys. 15, 1145-1149 (2019)]carries over to transition metal-containing compounds and is expected to play an essential role for a wide range of such materials. Knowledge of independent particle and collective response is essential for fully understanding these materials.

Compound Semiconductors

CSW’2022 continued the tradition of bringing together the compound semiconductor community to discuss the most recent advances in the field. After the successful meetings in Stockholm, Sweden in 2021 (held virtually due to Covid-19), Nara, Japan (2019), and Boston, USA in 2018, CSW came back to the US, to the beautiful college town of Ann Arbor, Michigan, a perfect setting to reunite the semiconductor community. As in previous years, CSW combined both the International Symposium on Compound Semiconductors (ISCS, now in its 48t year) and International Conference on Indium Phosphide and Related Materials (IPRM, in its 33rd year) conferences into a single integrated event. ISCS, established in 1966, is the preeminent international conference in the field of III–V, II–VI, and IV–IV semiconductors, whereas IPRM is, since 1989, a major worldwide conference on indium phosphide and related materials, from physics to applications. CSW’2022 was successfully organized during June 1–3, 2022, presenting 4 plenary talks, 2 tutorials, 37 invited talks, 94 contributed talks and 107 posters among an audience spread over Europe, Asia, and North America. In order that these contributions may meet even a wider audience, Wiley offered the authors an opportunity to publish their papers in physica status solidi (a). This resulted in this special issue of physica status solidi (a) containing 12 papers related to applications and materials science of compound semiconductors. The conference abundantly covered topics from “Materials Characterization” and “Device technologies”, to “Physics of Emerging Devices”, allowing the community to engage in fruitful discussions. This year CSW launched a special event to welcome “New Faces” in compound semiconductors and continued the tradition of rump sessions. Overall, we had about 252 registrants, their participation showing a healthy sign of return to in-person events! We gratefully acknowledge the substantial support received from individuals and organizations that helped us to make CSW’2022 a successful event: the technical program committee for efficiently evaluating all the submitted abstracts; the IEEE Electron Devices Society, IEEE conference management team, and all our industrial sponsors and exhibitors for their financial support; the local organizing committee as well as the ISCS and IPRM steering committees for practical support and guidance. Thanks to Ann Stals (University of Michigan) for all her help in the event management. Finally, our special appreciation goes to Drs. Stefan Hildebrandt and Marc Zastrow, and their team at Wiley for bringing out this special issue. Guest Editors: Grace Xing, Zetian Mi, and Srabanti Chowdhury

What Will Win the Wide-Bandgap Wars?

The answer is a resounding yes. Such a change is actually well underway. Starting around 2001, the compound semiconductor gallium nitride fomented a revolution in lighting that has been, by some measures, the fastest technology shift in human history. In just two decades, the share of the global lighting market held by gallium-nitride-based light-emitting diodes has gone from zero to more than 50 percent, according to a study by the International Energy Agency. The research firm Mordor Intelligence recently predicted that, worldwide, LED lighting will be responsible for cutting the electricity used for lighting by 30 to 40 percent over the next seven years. Globally, lighting accounts for about 20 percent of electricity use and 6 percent of carbon dioxide emissions, according to the United Nations Environment Program.

Changes to the Editorial Board

It is my pleasure to welcome Dr. Srabanti Chowdhury to the editorial board of IEEE Electron Device Letters. A biography and picture of Dr. Chowdhury can be found below. Her subject areas are compound semiconductor devices, solid-state power and high-voltage devices, materials, processing, and packaging.

Electronic Properties of Magnetic Semiconductor Compounds TlFeS2 and TlFeSе2

Electronic Properties of Magnetic Semiconductor Compounds TlFeS2 and TlFeSе2

Photoactive materials and devices for energy-efficient soft wearable optoelectronic systems

Advances in conventional inorganic photoactive materials, such as silicon and III–V compound semiconductors, enabled the development of high-performance and energy-efficient optoelectronic devices (e.g., photodetectors (PDs), light-emitting devices (LEDs), and photovoltaics (PVs)). These devices have recently been considered as essential components for multifunctional wearables that are capable of either providing a long-term stable power supply or visualizing various healthcare indicators in real time. Despite such progress, their rigid and bulky properties pose undesired challenges associated with low signal-to-noise ratios (SNRs) originating from a mechanical modulus mismatch between the skin and device, uncontrolled strain-induced crack propagation, and even long-term discomfort. As alternatives, emerging photoactive materials, such as atomically thin two-dimensional (2D) nanosheets and organic–inorganic halide perovskites with ultra-lightweight, ultrathin, and flexible characteristics have been significantly explored. These materials showed low-power multispectral sensing, effective light-matter coupling, and high compatibility to existing micro-/nano-fabrication technologies even on curved surfaces. Considering stretchability beyond flexibility, numerous research groups have employed well-established mechanical designs including a pre-strain-induced buckled structure with ultrathin layers, neutral-mechanical plane, and rigid-island array configuration with wavy interconnects. Recently, in addition to the above methodology, novel materials strategies regarding intrinsic stretchability and autonomous self-healability were introduced to improve the areal density and electrical/mechanical reliability through removal of serpentine interconnects, as well as adoption of tough damage-resistant polymers with efficient strain dissipation, low glass-transition temperature, and dynamically crosslinked bonds. In this light, the aforementioned methods would be essential to make current flexible photoactive devices intrinsically and durably stretchable. Here, we provide an overview of high-performance photovoltaic/photoemissive materials and devices and their applications to soft wearable energy-efficient optoelectronic systems. In particular, materials synthesis, device fabrication/assembly, and reconfigurable integration used in photoactive material-based wearable modular optoelectronic systems were timely described through a rigorous review of recent results.

Mid-wave infrared optical receiver based on an InAsSb-nBn photodetector using the barrier doping engineering technique for low-power satellite optical wireless communication.

This paper proposes a new nBn photodetector (nBn-PD) based on InAsSb with a barrier doping engineering technique [core-shell doped barrier (CSD-B) nBn-PD] for utilization as a low-power receiver in satellite optical wireless communication (Sat-OWC) systems. In the proposed structure, the absorber layer is selected from an I n A s 1-x S b x (x=0.17) ternary compound semiconductor. The difference between this structure and other nBn structures is the placement of the top and bottom contacts in the form of a PN junction, which increases the efficiency of the proposed device through the creation of a built-in electric field. Also, a barrier layer is placed from the AlSb binary compound. The presence of the CSD-B layer with the high conduction band offset and very low valence band offset improves the performance of the proposed device compared to conventional PN and avalanche photodiode detectors. By applying -0.1V bias at 125K, the dark current is demonstrated at 4.31×10-5 A/c m 2 by assuming high-level traps and defect conditions. Examining the figure of merit parameters under back-side illumination with a 50% cutoff wavelength of 4.6µm shows that at 150K, the responsivity of the CSD-B nBn-PD device reaches about 1.8A/W under 0.05W/c m 2 light intensity. Regarding the great importance of using low-noise receivers in Sat-OWC systems, the results indicate that the noise, noise equivalent power, and noise equivalent irradiance are calculated as 9.98×10-15 A H z -1/2, 9.21×10-15 W H z 1/2, and 1.02×10-9 W/c m 2, respectively, at -0.5V bias voltage and 4µm laser illumination with the influence of shot-thermal noise. Also, D ∗ obtains 3.26×1011 c m H z 1/2/W without using the anti-reflection coating layer. In addition, since the bit error rate (BER) plays an essential role in the Sat-OWC systems, the effect of different modulations on the BER sensitivity of the proposed receiver is investigated. The results represent that the pulse position modulation and return zero on-off keying modulations create the lowest BER. Attenuation is also investigated as a factor that significantly affects BER sensitivity. The results clearly express that the proposed detector provides the knowledge to achieve a high-quality Sat-OWC system.

Investigation of thermal dependence of phonon frequencies, sound velocity, mechanical and optical characteristics of the β-GaN semiconductor compound

Investigation of thermal dependence of phonon frequencies, sound velocity, mechanical and optical characteristics of the β-GaN semiconductor compound

Porous Semiconductor Compounds with Engineered Morphology as a Platform for Various Applications

Porous semiconductor compounds represent a class of materials which is under an intense research focus over the last years. Herein, morphologies and topologies produced by anodization in binary semiconductor compounds having various bandgaps and crystallographic orientations are demonstrated with a focus on technological procedures applied for generating arrays of pores with a controlled design. The mechanism of pores growth under the photoresist masks is discussed and the connection between the design of the mask and the architecture of the produced porous structure is disclosed. The evolution of physical characteristics of the materials such as luminescence, optical, photonic, vibrational, hydrophilic, and hydrophobic properties as a result of anodization is investigated. Investigations are performed by means of scanning electron microscopy, photoluminescence and cathodoluminescence spectroscopy, and contact angle measurements. Some possible practical applications of the proposed technological approaches and the produced porous structures are briefly discussed.

Bandgap energy prediction of senary zincblende III–V semiconductor compounds using machine learning

Two complimentary machine learning (ML) models are developed to estimate the bandgap energy (Eg) of senary zincblende (ZB) III–V semiconductor compounds Alx1Gax2Inx3Py1Asy2Sby3 from molar fractions. The models work – as well – for any compound with smaller number of constituent elements from binaries to quinaries. Some of these compounds exhibit transition between a direct and an indirect Eg as a function of composition. This is due to the fact that the bandgap for this class of materials is either the direct gap at Γ point (EgΓ) or the indirect one between the maximum valance band at Γ point and the minimum conduction band around X point (EgX). Hence, to capture precisely the Eg and its state, the ML models estimate separately the EgΓ and EgX where the lowest energy gap is the effective Eg. For model training, 18 ternary ZB III–V semiconductor compounds are used, which contain all possible ternary configurations of III-type cations (Al, Ga, In) and V-type anions (P, As, Sb). The achieved testing accuracy using cubic regression with ridge regularization – in terms of root mean square error (RMSE) – are 7.583 and 0.021 meV for EgΓ and EgX, respectively. These correspond to R2 of 0.99995 and 1.00000 (8 nines), respectively. To validate the models, they are benchmarked against experimental measurements of four different quaternary ZB III–V semiconductor compounds. The agreement is very noticeable demonstrating the validity and the excellent accuracy of the developed models.

Enhancement in Efficiency of CIGS Solar Cell by Using a p-Si BSF Layer

Copper–indium–gallium–diselenide Cu(In,Ga)Se2 (CIGS) is a semiconductor compound belonging to group I-III-VI, with a chalcopyrite crystal structure. CIGS is promising for the development of high-performance photovoltaic applications in terms of stability and conversion efficiency. It is one of the main candidates to rival the efficiency and stability of conventional crystalline silicon cells, due to its high light absorption coefficient, lower material cost, and high stability. The limitation of its use is that CIGS integrates indium (In) and gallium (Ga), which are rare and expensive materials. The amount of these materials in the CIGS cell can be reduced by optimizing the thickness of the absorber. We show that the introduction of a layer of highly doped silicon in the structure of the solar cell between the absorber layer and the back surface field layer effectively allows for decreasing the thickness of the absorber. Within the same objective, we focus on the danger of cadmium in the CdS buffer layer. In the first optimizations, we replaced the n-type CdS buffer layer with a n-type Zn(O,S) buffer layer. For this work, we used a one-dimensional simulation program, named Solar Cell Capacitance Simulator in one Dimension (SCAPS-1D), to investigate this new CIGS solar cell structure. After optimization, a maximum conversion efficiency of 24.43% was achieved with a 0.2 μm CIGS absorber layer and a 1 µm Si BSF layer.

High-throughput manufacturing of epitaxial membranes from a single wafer by 2D materials-based layer transfer process

Layer transfer techniques have been extensively explored for semiconductor device fabrication as a path to reduce costs and to form heterogeneously integrated devices. These techniques entail isolating epitaxial layers from an expensive donor wafer to form freestanding membranes. However, current layer transfer processes are still low-throughput and too expensive to be commercially suitable. Here we report a high-throughput layer transfer technique that can produce multiple compound semiconductor membranes from a single wafer. We directly grow two-dimensional (2D) materials on III-N and III-V substrates using epitaxy tools, which enables a scheme comprised of multiple alternating layers of 2D materials and epilayers that can be formed by a single growth run. Each epilayer in the multistack structure is then harvested by layer-by-layer mechanical exfoliation, producing multiple freestanding membranes from a single wafer without involving time-consuming processes such as sacrificial layer etching or wafer polishing. Moreover, atomic-precision exfoliation at the 2D interface allows for the recycling of the wafers for subsequent membrane production, with the potential for greatly reducing the manufacturing cost.

In-Plane Anisotropic Rectification and Photovoltaic Effects on ZnO Nonpolar (101̅0) Crystal Plane and the Physical Mechanism.

The concept of spontaneous electric field (Es) in polar structures is crucial for understanding the physical and chemical properties of compound semiconductors and improving their performanes. However, this concept has not been widely accepted so far. Here, we show the first observation of rectification and photovoltaic effects in the polar [0001] direction on the nonpolar ZnO (1010) crystal plane. However, no rectification and photovoltaic effects are observed in the nonpolar [1210] direction perpendicular to the [0001]. When a stress was applied in the [0001] direction of the ZnO single crystal, the rectification and photovoltaic effects are abated and disappeared. The disappearance of the two effects results from the pressure-induced disappearance of the polar structure. The results fully demonstrated that the rectification and photovoltaic effects arise from the existence of Es in the polar [0001] direction. The Es motivates the directional transfer of the electrons and photocreated charges along the [0001] direction, and the rectification and photovoltaic effects are thus observed. These results provide direct evidence for the polar structure theory and suggest that the polar structures can be employed to develop new types of photovoltaic and other electronic and photoelectronic devices.

Isolation and Characterisation of High Grade Nanosilicon from Coastal Landform in Ilaje Local Government Area of Ondo State, Nigeria.

The application of silicon and silicon based materials in industries and optoelectronic devices cannot be over emphasized due to their unique properties. The availability of high grade silicon has been subject of interest for manufacturers and industrialist as the material has from discovery been very much insufficient to cater for the numerous demands for different uses and utilization. Numerous efforts have been put together to adapt the properties of silicon through the manufacture and fabrication of semiconductor compounds to replace silicon in functionality. Notwithstanding, the quest for more silicon in the environment is yet unabated. This research centers on the isolation and characterisation of high grade nanosilicon from coastal landform in Ilaje Local Government Area of Ondo State, Nigeria due to the attractive nature of the landforms in terms of colour and texture. Sand from the selected study area were categorised into different forms according to their colour and silicon isolated using the magnesiothermic reduction while the nanosilicon was obtained using an appropriate ball milling process. The morphology of nanosilicon from Zion, Micheal-Ugbonla, and Oluwa Glass coastal landforms shows an agglomeration of particles with irregular shapes having average particle sizes of 58.98 nm, 77.82 nm, and 37.27 nm, respectively. The XRD spectra of the nanosilicon showed sharp, distinct peaks that indicate crystallinity of the samples. The percentages of nanosilicon value obtained ranges from 65.23%-80.30% and considered high enough to find specific useful industrial applications in lithium ion batteries, biomedical devices, opto electronic device utilization and computer industries.

Sustainable solvent metal lift-off for compound semiconductor fabrication with improved manufacturability

Due to concerns regarding substrate damage, wet photoresist removal has been adopted over dry etch techniques for certain metal lift-off processes on substrates and metals that are susceptible to plasma damage. Wet photoresist removal generally requires the use of polar aprotic solvents and historically n-methyl pyrrolidone (NMP) has been broadly adopted. A successful lift-off process requires consideration of both the solvent used to remove the photoresist as well as the correct photoresist retrograde profile. As features become smaller and more critical, the overall photoresist profile becomes more challenging. The use of bottom anti-reflective coatings (BARC) has become necessary to better control the reflected light and minimize potential defectivity during patterning. However, addition of the BARC layer complicates the resist removal process by requiring a secondary cleaning step since wet photoresist strip chemistries, such as NMP, generally do not remove it. There have been several developmental efforts in the metal lift-off industry to formulate a solvent, which could remove both photoresist and BARC, concurrently. In the first half of this paper, various wet photoresist removers are compared to determine the most effective wet resist strip for removal of both photoresist and BARC in one step. The second half of the paper summarizes two different metal liftoff processes and compares the performance of the best chemistry from initial experimentation, Technistrip® MLO-07, to NMP.

Electrodeposition of Cadmium Selenide Based Photoanodes from TOMAC/Formamide Ionic Liquid System for Photoelectrochemical Water Splitting

The electrodeposition from room temperature ionic liquids (RTILs) has recently come up as a low-cost technique for the growth of II–VI semiconductor compounds and thin films, some promising alternatives to classical organic or inorganic solvents. As a relatively new field of study, only a few reports exist describing the growth mechanism of electrodeposition from RTILs, especially for CdSe films. In this paper, a new electrochemical method has been developed for the deposition of Cadmium Selenide thin layers onto indium doped tin oxide coated conducting glass (ITO) using an RTIL and an Organic solvent system (Tricaprylmethylammonium chloride/Formamide). Structural properties of prepared films have been investigated by X-ray diffraction (XRD) and micro-Raman analysis which reveal a pure cubic phase with the zinc-blende-type structure and typical peaks of nanostructured CdSe, respectively. Atomic force microscopy (AFM) analysis showed homogenous and smooth surface of the deposited films. UV-vis measurements demonstrated the presence of direct transition with a band gap energy around 1.68[Formula: see text]eV. The flat-band potential and carrier density values of CdSe thin film are [Formula: see text]0.667[Formula: see text]V and [Formula: see text][Formula: see text]cm[Formula: see text], respectively, as deduced from Mott–Schottky studies. The photoelectrochemical (PEC) behavior of the CdSe thin film exhibited an enhanced photocurrent density at about 0.35[Formula: see text]mA/cm2 vs. Ag/AgCl.