Quaternary Semiconductor Research Articles

Machine learning for accelerated bandgap prediction in strain-engineered quaternary III-V semiconductors.

Quaternary III-V semiconductors are one of the most promising material classes in optoelectronics. The bandgap and its character, direct or indirect, are the most important fundamental properties determining the performance and characteristics of optoelectronic devices. Experimental approaches screening a large range of possible combinations of III- and V-elements with variations in composition and strain are impractical for every target application. We present a combination of accurate first-principles calculations and machine learning based approaches to predict the properties of the bandgap for quaternary III-V semiconductors. By learning bandgap magnitudes and their nature at density functional theory accuracy based solely on the composition and strain features of the materials as an input, we develop a computationally efficient yet highly accurate machine learning approach that can be applied to a large number of compositions and strain values. This allows for a computationally efficient prediction of a vast range of materials under different strains, offering the possibility of virtual screening of multinary III-V materials for optoelectronic applications.

Pitfalls in cation alloying of quaternary chalcogenide semiconductors

Pitfalls in cation alloying of quaternary chalcogenide semiconductors

Assessment of deep levels with selenium concentration in Cd1–xZnxTe1–ySey room temperature detector materials

Incorporation of Se into Cd1−xZnxTe (CZT) to form the quaternary compound semiconductor Cd1−xZnxTe1–ySey (CZTS) has proven to be an effective solution for compensating the major flaws associated with CZT, including poor homogeneity and high concentrations of electronically active deep levels that limit the performance of CZT detectors. In order to investigate how deep levels are affected by the Se concentration in CZTS, we performed photoinduced current transient spectroscopy (PICTS) measurements on CZTS crystals grown by the traveling heater method (THM) with 10% atomic Zn and varying atomic percentage of Se from 1.5% to 7.0%. The PICTS scans for up to 4% Se showed an exponential reduction in the capture cross section of deep levels associated with Te secondary phases in conjunction with an increase in a deep level positioned near the mid-gap, which initially increases the electron trapping time before degrading again at higher Se concentrations. The PICTS peaks present in 7% Se were anomalous relative to the other crystals and are expected to originate from transition metal impurities found in the lower-purity CdSe precursor material.

Experimental and computational study of Cu2FeSnS4: An emerging quaternary semiconductor

The quaternary semiconductor Cu2FeSnS4 (CFTS) has attracted attention of the research community due to its optical and electrical properties, earth abundance and non-toxicity. CFTS powder has been successfully synthesized using solvothermal technique. X-ray diffraction peaks and Raman spectra confirm structural formation of the compound, and XPS studies determine the oxidation states of Cu, Fe, Sn and S to be +1, +2, +4 and −2 respectively. The scanning electron microscopy images show nanosheet array-like morphology and the stoichiometry ratio of 2:1:1:4 for Cu, Fe, Sn and S respectively is obtained from EDS measurements. Direct band gap of 1.52 eV has been estimated using the Tauc plot. The experimental findings have been supported computationally using density functional theory (DFT) based calculations performed within quantum espresso (QE) software. The stannite phase is observed to be the ground state and is in accordance with the experimental observation. The total density of states (DOS) and projected DOS show the contribution of each elemental species in valence and conduction bands. A direct band gap of 1.51 eV obtained from HSE06 hybrid functional is in good agreement with the Tauc plot result. Further, the cation defect formation calculations show that Cu vacancy is most likely to be formed among the cations. The computationally obtained absorption spectra confirms the application of CFTS as absorber layer in a solar cell. The electrical study of the p-CFTS and n-CdS junction is carried out using J-V response. The calculated ideality factor, series resistance and power conversion efficiency show promising application in photovoltaic industry. The present work fills the existing gap in the published literature of a systematic experimental and computational study of CFTS semiconductor, which has application in varied fields.

Solvothermal synthesis of CMTS quaternary semiconductor nanoparticles with a symmetric kesterite structure: The role of the autoclave filling factor

Copper manganese tin sulfide (CMTS) is one of the promising chalcogenide materials and a potential candidate as an absorber material to develop low-cost, ultrathin solar cells. CMTS (Cu2MnSnS4) quaternary semiconductor nanoparticles (NPs) were synthesized by a solvothermal method utilizing different autoclave filling ratios. The influence of the autoclave filling ratio on the structure, phase formation, morphology, composition and optical properties of the CMTS-NPs was studied using various experimental techniques. The autoclave was filled with a solution up to 50, 60 and 70 percent of the autoclave volume. According to the FESEM images, the CMTS-NPs are uniform, dense and spherical, with slight agglomeration. The CMTS particles have an average crystal size in the range of 31 to 40 nm for different autoclave filling ratios. The chemical composition for CMTS was obtained from SEM – EDX and it was found that the sample with 60% filling factor had the best structure, with the atomic percentages of Cu: 26%, Mn: 9%, Sn: 12%, and S: 53%, which are close to the optimal values. The XRD results showed that the composition of the product was close to the stoichiometry of CMTS, with a Kesterite structure. Investigation of different autoclave filling factors showed that 60% is an optimum filling rate to obtain the CMTS pure phase with high crystallinity. The CMTS particles had a broad absorption band in the whole visible range with a band gap of 1.38 eV, being promising for photovoltaic applications.

Development of phase pure Cu2ZnSiSe4 via solid state synthesis for energy applications

In recent years, quaternary diamond-like metal chalcogenide semiconductor nanocrystals have received a lot of attention in solar cell and thermoelectric applications. The optoelectronic properties of quaternary diamond-like structures are influenced by their crystal structure. In this work, a series of experiments have been performed to understand the crystal system of Cu2ZnSiSe4 materials via solid state synthesis, namely mechanosynthesis to get a single phase of quaternary chalcogenide via single step route synthesis. The materials were performed at different milling time to study the single phase compound and phase transformation of the materials. Based on the theory and existing literature, the composition of the materials has been selected as 2:1:1:4 which is the optimum composition for quaternary chalcogenides. Based on the composition, the material properties will be changed. X-ray diffraction (XRD) and Raman spectroscopy were used to analyse the structure and phase purity of Cu2ZnSiSe4 nanoparticles. Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray spectroscopy (EDS) results showed that the average size of the Cu2ZnSiSe4 particles and the composition of products were close to the stoichiometry of Cu2ZnSiSe4. Optical studies show that Cu2ZnSiSe4 nanocrystals exhibit good, strong optical absorption in the visible region of the electromagnetic spectrum and a 1.12 eV bandgap. Hall measurement shows the bulk property of the materials and it is inferred that the synthesized materials show p-type conductivity in bulk. The obtained compound possesses good structural and optoelectronic behavior and hence could be utilized as effective solar absorber in thin film solar cells.

Developing a magnetic bismuth-based quaternary semiconductor boosted by plasmonic action for photocatalytic detoxification of Cr(VI) and norfloxacin antibiotic under simulated solar irradiation: Synergistic work and radical mechanism

The development of robust dual-S-scheme heterojunctions has exhibited prominent potential for the photo-degradation of environmental pollutants. Herein, novel dual-S-scheme heterojunction of NiFe2O4/Bi/Bi2WO6/Bi5O7I was constructed by a facile multistep approach for pollutants detoxification under visible-light illumination. The novelty of this work involved the incorporation of a bismuth-based heterostructure with NiFe2O4 to develop a magnetic field for recycling issues. The morphological characteristics revealed the presence of NiFe2O4/Bi/Bi2WO6/Bi5O7I (NFO/BBWO/BOI) in a flower-like structure. The NFO/BBWO/BOI heterojunction displayed the highest photocatalytic activity towards NOR destruction (96.5% in 75 min) and Cr(VI) reduction (95% in 60 min) under LED illumination. The synergistic work between the S-scheme heterojunction and the plasmonic (SPR) effect was behind the boosted photocatalytic performance. On the other hand, the influence of some environmental factors like pH, organic and inorganic substances, catalyst loading, and actual water bodies was also discussed. Besides, NFO/BBWO/BOI reflected facile reusability and excellent stability. The radical detection tests demonstrated the significant participation of all reactive species in NOR oxidation. The photodegradation pathways and intermediates detection of NOR were accurately proposed using the HPLC-TOF-MS system. Finally, the suggested mechanism declared that the synergistic efforts of SPR action and the S-scheme system could effectively stimulate the charge migration with high redox potential to mineralize the NOR and Cr(VI) reduction under visible light illumination.

Relationships between Compositional Heterogeneity and Electronic Spectra of (Ga1–xZnx)(N1–xOx) Nanocrystals Revealed by Valence Electron Energy Loss Spectroscopy

Many ternary and quaternary semiconductors have been made in nanocrystalline forms for a variety of applications, but we have little understanding of how well their ensemble properties reflect the properties of individual nanocrystals. We examine electronic structure heterogeneities in nanocrystals of (Ga1–xZnx)(N1–xOx), a semiconductor that splits water under visible illumination. We use valence electron energy loss spectroscopy (VEELS) in a scanning transmission electron microscope to map out electronic spectra of (Ga1–xZnx)(N1–xOx) nanocrystals with a spatial resolution of 8 nm. We examine three samples with varying degrees of intraparticle and interparticle compositional heterogeneity and ensemble optical spectra that range from a single band gap in the visible to two band gaps, one in the visible and one in the UV. The VEELS spectra resemble the ensemble absorption spectra for a sample with a homogeneous elemental distribution and a single band gap and, more interestingly, one with intraparticle compositional heterogeneity and two band gaps. We observe spatial variation in VEELS spectra only with significant interparticle compositional heterogeneity. Hence, we reveal the conditions under which the ensemble spectra reveal the optical properties of individual (Ga1–xZnx)(N1–xOx) particles. More broadly, we illustrate how VEELS can be used to probe electronic heterogeneities in compositionally complex nanoscale semiconductors.

Heterogeneity of grain boundary properties in Cu2ZnSnS4: A first-principles study

Using first-principles density functional calculations, we investigate the structure and properties of previously unstudied grain boundaries (GBs) in the solar absorber material copper-zinc-tin-sulfide (CZTS). We identify four stable low-Σ value symmetric tilt GBs with low formation energies: Σ3 (111) and Σ5 (201), each with two different GB terminations. Compared to CdTe and CuInSe, GBs in the quaternary semiconductor CZTS exhibit a wider variety of electronic states due to the more complex chemical environment near the GB, including under-coordinated atoms and dangling bonds. Further analysis confirms that strong dangling bonds introduce deep gap states in all GBs studied. We also investigate segregation and electronic properties of intrinsic point defects to GBs and find that one of the Σ3 (111) GBs exhibits an abnormal defect segregation behavior that favors Cu-poor (Zn-rich) GB composition, which is beneficial for its overall performance.

Defect manipulations in the quaternary semiconductor Y2Ti2O5S2: The DFT insights

Oxysulfide semiconductor Y2Ti2O5S2 (YTOS) is a new kind of narrow band gap photocatalyst for water splitting in the range of visible light. However, it suffers from rapid electron-hole recombination and sluggish surface reaction, possibly due to unknown intrinsic defect properties. Here, we use an algorithm involving chemical potentials to investigate intrinsic defects in YTOS, and directly reveal the primary formation of antisites and anion vacancies under experimentally favorable conditions. In particular, oxygen vacancy (VO) in YTOS causes a large difference in effective mass between electron and hole, and improves the carrier separation efficiency. The change of VO concentration can further enhance the visible light absorption. This work discovers the role of defects in affecting electron-hole separation at the atomic level, and provides new opportunities for achieving highly efficient water splitting performances.

Record-High Work-Function p-Type CuBiP2 Se6 Atomic Layers for High-Photoresponse van der Waals Vertical Heterostructure Phototransistor.

The notable lack of intrinsic p-type 2D layered semiconductors has hindered the engineering of 2D devices for complementary metal oxide semiconductors (CMOSs). Herein, a novel quaternary intrinsic p-type 2D semiconductor, CuBiP2 Se6 atomic layers, is introduced intothe2D family. The semiconductor displays a high work function of 5.26eV, a moderate hole mobility of 1.72 cm2 V-1 s-1 , and an ultrahigh on/off current exceeding 106 at room temperature. To date, 5.26eV is the highest work-function recorded in p-type 2D materials, indicating the ultrastable p-type behavior of CuBiP2 Se6 . Additionally, a multilayer graphene/CuBiP2 Se6 /multilayer graphene (MLG/CBPS/MLG)-based fully vertical van der Waals heterostructure phototransistor is designed and fabricated. This device exhibits outstanding optoelectronic performance with a responsivity (R) of 4.9 ×104 A W-1 , an external quantum efficiency (EQE) of 1.5 ×107 %, a detectivity (D) of 1.14 ×1013 Jones, and a broad working wavelength (400-1100nm), respectively. This is comparableto state-of-the-art 2D devices. Such excellent performance is attributed to the ultrashort transmit length and nondestructive/defect-free contacts. This leads to faster response speed and eliminates Fermi-levelpinningeffects. Moreover, ultrahigh responsivity and detectivity endow the device with applaudable imaging sensing capability. These results make CuBiP2 Se6 an ideal p-type candidate material for next-generation CMOSs logic devices.

Investigating the structural, electronic, and elastic properties of Li-based quaternary Heusler alloy semiconductors using hybrid functional – HSE06 bandgap recalculations

In this work, we introduce a new class of stable semiconducting equiatomic quaternary Heusler alloys. The 21 new semiconductors reported in this work contain 18 valence electrons per unit cell.Three different structural arrangements, referred Y1,Y2 and Y3 are taken into consideration. The bandgaps are investigated and significantly underestimated by GGA-PBE functional. We recalculated them by means of the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional to achieve the correct ones. This study shows that the HSE06 correction mainly acts on the lowest conduction bands. The energy gaps of the quaternary Heusler semiconductors are in the range of 0.766–1.94 eV, which suggests that these semiconductors are prospective materials for a variety of applications, including thermoelectric, optoelectronic, and photovoltaic. Furthermore, formation energy, elastic constants, and phonon dispersion curves are calculated to verify the mechanical and dynamical stabilities of these alloys.

Electronic, mechanical, optical and thermodynamic properties of the quaternary semiconductors Sr3GeMgN4 and Ba3GeMgN4

The electronic structure, optical and thermodynamic properties of M3GeMgN4 (M = Sr or Ba) nitrides have been investigated using first-principles calculations. The calculated equilibrium lattice parameters and inter-atomic bond-lengths show excellent concordance with experiment. The elastic constants (Cijs) and their derived properties have been calculated showing that the examined compounds are mechanically stable and elastically soft, ductile and anisotropic. The analysis of the electronic structure reveals a semiconductor comportment for both crystals. The Sr3GeMgN4 (Ba3GeMgN4) compound possesses a direct (indirect) energy gap of 1.476 eV (1.194 eV). The chemical bonding in both semiconductors is dominated by a covalent character, which originates from the Ge-N and Mg-N hybridized states. Both nitrides show moderate dielectric properties, high visible and UV absorbance, indicating that both materials are suitable for optoelectronic applications. Phononic dispersion curves have demonstrated the dynamical stability of the studied crystals.

Facile High-Yield Synthesis of Ag–In–Ga–S Quaternary Quantum Dots and Coating with Gallium Sulfide Shells for Narrow Band-Edge Emission

Among cadmium-free quantum dots (QDs), ternary or quaternary chalcogenide semiconductor QDs composed of groups 11, 13, and 16 elements have extensively been studied. Herein, monodispersed quaternary nanoparticles of silver indium gallium sulfide (AgInxGa1–xS2) are synthesized by a new route that specifically produces the target product without solid byproducts. The difference in the reactivity between groups 11 and 13 metals with chalcogen is a common issue in synthesizing the groups 11, 13, and 16 ternary or quaternary semiconductor QDs. Instead of a common approach to suppress the reactivity of group 11 metals, this study utilizes their high reactivity; rapid injection of a Ag source into the solution containing a thiocarboxylate produced small Ag2S nanoparticles. These Ag2S nanoparticles are then exposed to indium-, gallium-, and sulfur-containing species in situ and then converted into quaternary nanoparticles comprising AgInxGa1–xS2. Due to the well-controlled reaction steps, the product yield based on Ag was increased to 60%, which significantly exceeds that obtained using our previous approach of heating all-mixed raw materials (5–15%). After coating with gallium sulfide (GaSy) shells, the core/shell QDs exhibited an intense, green-colored band-edge emission with a tunable peak wavelength between 499 and 543 nm. The excellent uniformity of the core nanoparticles in terms of size and composition demonstrated a quite narrow band-edge emission with the full width at half maximum of 31 nm, which is equal to the record-narrow values of green-emitting cadmium-free QDs. Additionally, a near-unity photoluminescence quantum yield was achieved after postsynthetic surface treatment by alkylphosphines, indicating the defect-free nature of the prepared AgInxGa1–xS2/GaSy core/shell QD system.

Machine learning and density functional theory simulation of the electronic structural properties for novel quaternary semiconductors.

In order to accelerate the application of quaternary optoelectronic materials in the field of luminescence, it is crucial to develop new quaternary semiconductor materials with excellent properties. However, faced with vast alternative quaternary semiconductors, traditional trial-and-error methods tend to be laborious and inefficient. Here, we combined machine learning (ML) with density functional theory (DFT) calculation to predict the bandgaps of 2180 quaternary semiconductors, most of which were undeveloped but environmentally friendly. The evaluation coefficient (R2) of the model using a random forest algorithm was up to 0.93 in ML. Four novel quaternary semiconductors with direct bandgaps: Ag2InGaS4, AgZn2InS4, Ag2ZnSnS4, and AgZn2GaS4, were selected from the ML model. Then their electronic structures and optical properties were further verified and studied by DFT calculations, which demonstrated that the four quaternary semiconductors had direct bandgaps, a small effective mass, and a large exciton binding energy and Stokes shift. Our calculation could significantly speed up the discovery of novel optoelectronic semiconductors and has a certain reference value for the study of luminescent materials and devices.

Construction of chalcogenide Cu2BaVS4 nanograins from nanocubes via solvothermal synthesis for photoelectrochemical hydrogen/oxygen evaluation in alkaline media and dye degradation applications

In this investigation, we report the synthesis of quaternary chalcogenide semiconductor Cu2BaVS4 (CBVS) nanostructures through the solvothermal method for the first time.

Cation and anion mutations in kesterites: A way to flexible band gap energy tuning

• Solar cells based on Kesterite-type absorber layers are the only critical raw material (CRM) free thin film PV technology. • Quaternary chalcogenide semiconductors, e.g. Cu 2 ZnGeS 4 /Se 4 or Cu 2 ZnSiSe 4 show band gap energies between 1.5 eV and 2.2 eV. • Flexible bandgap energy tuning in compound semiconductors is possible by cation and anion mutation (alloying). • Different alloying schemes (e. g. anion alloying or cation alloying) show various special features (e. g. miscibility gap).

Influence of Hydrophilic Thiol Ligands of Varying Denticity on the Luminescence Properties and Colloidal Stability of Quaternary Semiconductor Nanocrystals

Influence of Hydrophilic Thiol Ligands of Varying Denticity on the Luminescence Properties and Colloidal Stability of Quaternary Semiconductor Nanocrystals

Effects of Periodic Pore Ordering on Photocatalytic Hydrogen Generation with Mesoporous Semiconductor Oxides

Crystalline and 3D continuous mesoporous quaternary CsTaWO6 semiconductors are prepared with different degrees of long‐range periodic order and local order, respectively, to investigate the influence of periodic pore order on the photocatalytic performance in hydrogen evolution of mesoporous photocatalysts. The degree of long‐range order of the mesopores is changed by modifying the ratio between metal precursors and soft polymer template poly(isoprene‐b‐styrene‐b‐ethylene oxide) (PI‐b‐PS‐b‐PEO; ISO) in the sol–gel synthesis. Long‐range periodic order is found to have no appreciable advantage compared with an only locally ordered continuous pore system. On the contrary, nonperiodically ordered mesopores result in higher activity toward photocatalytic hydrogen evolution, even with slightly smaller pore diameter and lower cumulative pore volume. Most importantly, it is shown that pore connectivity and heterogeneous pore systems in mesoporous photocatalysts play a major role for hydrogen evolution when other parameters are confirmed to be not rate limiting.

CRYSTAL STRUCTURE OF AgGa2Te3I COMPOUND

A compound AgGa2Te3I belongs to the quaternary semiconductors of the general formula AІВІІІ2X3Y (AІ – Cu, Ag; ВІІІ – Ga, In; X – S, Se, Те; Y - Cl, Br, I). For the first time, its structure, which forms in tetragonal syngony, was studied by the powder method, Sp.Gr. I-4, structural type CuIn2Te3Cl, with cell parameters: a = 6,0041 (4) Å, c = 11,965 (1) Å. The compound was synthesized in evacuated quartz ampoules from simple substances and pre-synthesized AgI by step heating. Based on the melting temperatures of the components, the 1070 K maximum synthesis temperature was chosen, followed by homogenizing annealing at 770 K during 300 h and subsequent quenching in water at room temperature. As a result of the synthesis, a compact, gray alloy was obtained, which was resistant to air. The diffraction pattern of the powdered sample was taken on a DRON 4-13 diffractometer, CuKα radiation, irradiation at one point during 15 sec. WinCSD program was used to calculate the structure, which was refined by the Rietveld method. The obtained results on the structure of the compound were analyzed and its belonging to defective semiconductors was discussed.