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We investigated the carrier dynamics of ammonothermal Mn-compensated gallium nitride (GaN:Mn) semiconductors by using sub-bandgap and above-bandgap photo-excitation in a photoluminescence analysis and pump–probe measurements. The contactless probing methods elucidated their versatility for the complex analysis of defects in GaN:Mn crystals. The impurities of Mn were found to show photoconductivity and absorption bands starting at the 700 nm wavelength threshold and a broad peak located at 800 nm. Here, we determined the impact of Mn-induced states and Mg acceptors on the relaxation rates of charge carriers in GaN:Mn based on a photoluminescence analysis and pump–probe measurements. The electrons in the conduction band tails were found to be responsible for both the photoconductivity and yellow luminescence decays. The slower red luminescence and pump–probe decays were dominated by Mg acceptors. After photo-excitation, the electrons and holes were quickly thermalized to the conduction band tails and Mg acceptors, respectively. The yellow photoluminescence decays exhibited a 1 ns decay time at low laser excitations, whereas, at the highest ones, it increased up to 7 ns due to the saturation of the nonradiative defects, resembling the photoconductivity lifetime dependence. The fast photo-carrier decay time observed in ammonothermal GaN:Mn is of critical importance in high-frequency and high-voltage device applications. [ABSTRACT FROM AUTHOR]

Abstract Environmental issues and the global need to increase economically sustainable access to electricity addressed and boosted scientific research and use of Distributed Energy Resources, such as solar Photovoltaic (PV). Multi‐port power converters can be of great interest for a compact and efficient interface between PV, storage units, and DC loads. The Triple Active Bridge (TAB) shows interesting advantages in terms of isolation and Zero Voltage Switching capabilities over wide load and input voltage ranges. This work aims to develop a TAB prototype for a NanoGrid (NG) application, analyzing the possibility of a direct interface of PV modules, storage units, and DC loads, without the use of intermediate conversion stages. The TAB prototype uses Gallium Nitride devices, and an evaluation of the overall efficiency is provided, useful to compare with other isolated three‐port converters. Through an analytical approach, a TAB has been sized and optimized to meet specific application requirements. MATLAB/Simulink simulations have been done for the sizing validation and the control strategy design. A prototype has been developed and experimental measurements have been compared with simulation results. The TAB is proposed as a key element of DC NGs, but applications of interest are also automotive, More Electric Aircraft, and naval applications.

Environmental issues and the global need to increase economically sustainable access to electricity addressed and boosted scientific research and use of Distributed Energy Resources, such as solar Photovoltaic (PV). Multi‐port power converters can be of great interest for a compact and efficient interface between PV, storage units, and DC loads. The Triple Active Bridge (TAB) shows interesting advantages in terms of isolation and Zero Voltage Switching capabilities over wide load and input voltage ranges. This work aims to develop a TAB prototype for a NanoGrid (NG) application, analyzing the possibility of a direct interface of PV modules, storage units, and DC loads, without the use of intermediate conversion stages. The TAB prototype uses Gallium Nitride devices, and an evaluation of the overall efficiency is provided, useful to compare with other isolated three‐port converters. Through an analytical approach, a TAB has been sized and optimized to meet specific application requirements. MATLAB/Simulink simulations have been done for the sizing validation and the control strategy design. A prototype has been developed and experimental measurements have been compared with simulation results. The TAB is proposed as a key element of DC NGs, but applications of interest are also automotive, More Electric Aircraft, and naval applications. [ABSTRACT FROM AUTHOR]

The discovery of mechanically soft solid‐state materials with fast Mg‐ion conduction is crucial for the development of solid‐state magnesium batteries. In this paper, novel magnesium gallium halide compounds are reported that achieve high ionic conductivity of 0.47 mS cm−1 at room temperature. These Mg‐ion conductors obtained by ball milling Mg and Ga salts exhibit clay‐like mechanical properties, enabling intimate contact at the electrode–electrolyte interface during battery cycling. With a combination of experimental and computational analysis, this study identifies that the soft‐clay formation is induced by partial anion exchange during milling. This partial anion exchange creates undercoordinated magnesium ions in a chlorine‐rich environment, yielding fast Mg‐ion conduction. This work demonstrates the potential of clay‐like halide electrolytes for all‐solid‐state magnesium batteries, with possible further extension to other multivalent battery systems. [ABSTRACT FROM AUTHOR]

Herein, the first F-containing iodate-phosphate, namely Ba2Ga2F6(IO3)(PO4), was prepared via a hydrothermal reaction, in which HPF6 (70 wt% solution in water) was used as the source of both fluoride and phosphate anions for the first time. Ba2Ga2F6(IO3)(PO4) features an unprecedented 1D [Ga2F6(IO3)(PO4)]4− helix chain, composed of a 1D Ga(1)(IO3)O4F chain via the bridging of 0D Ga(2)(PO4)F5. The UV-Vis spectrum shows that Ba2Ga2F6(IO3)(PO4) has a wide bandgap with a short-UV absorption edge (4.35 eV; 253 nm). Birefringence measurement under a polarizing microscope shows that Ba2Ga2F6(IO3)(PO4) displays a moderate birefringence of 0.072@550 nm, which is consistent with the value (0.070@550 nm) obtained by DFT calculations, indicating that Ba2Ga2F6(IO3)(PO4) has potential applications as a short-UV birefringent material. This study highlights the crucial role played by the incorporation of specific functional groups into compounds, shedding light on their contribution to promising inorganic functional materials. [ABSTRACT FROM AUTHOR]

This study explored the inhibitory potential of gallium maltolate against severe acute respiratory syndrome coronavirus 2 and main and papain-like proteases. Computational methods, including density functional theory and molecular docking, were used to assess gallium maltolate reactivity and binding interactions. Density functional theory calculations revealed gallium maltolate's high electron-capturing capacity, particularly around the gallium metal atom, which may contribute to their activity. Molecular docking demonstrated that gallium maltolate can form strong hydrogen bonds with key amino acid residues like glutamate-166 and cysteine-145, tightly binding to main and papain-like proteases. The binding energy and interactions of gallium maltolate were comparable to known SARS-CoV-2 inhibitors like N-[(5-methyl-1,2-oxazol-3-yl)carbonyl]-L-alanyl-L-valyl-N-{(2S,3E)-5-(benzyloxy)-5-oxo-1-[(3S)-2-oxopyrrolidin-3-yl]pent-3-en-2-yl}-L-leucinamide, indicating its potential as an antiviral agent. However, further experimental validation is required to confirm its effectiveness in inhibiting SARS-CoV-2 replication and treating COVID-19. [ABSTRACT FROM AUTHOR]

Lewis superacids (LSA) are defined by a fluoride ion affinity (FIA) that exceeds that of SbF5, and are thus characterized as hard according to the HSAB concept. Soft superacidity was defined for compounds exceeding the hydride ion affinity (HIA) of B(C6F5)3. Herein we report on the synthesis of a Lewis acid being superacidic only on the soft regime: tris(pentafluoroethyl)indane, In(C2F5)3. It is accessible in the form of its dihydrate [In(C2F5)3(OH2)2]. An improved synthesis for the gallium analogue [Ga(C2F5)3(OH2)2] is also reported. Tris(pentafluoroethyl)indane dihydrate, [In(C2F5)3(OH2)2], was fully characterized by IR and NMR spectroscopy, as well as by single crystal X‐ray diffraction. Due to their stability and convenient accessibility, the hydrates are ideal starting compounds for the chemistry of tris(pentafluoroethyl)gallium and ‐indium compounds, for example hydroxogallates and ‐indates. An attempt to determine its gas‐phase structure and that of the gallium analogue by electron diffraction demonstrates that they lose water ligands upon evaporation. The energetics of these processes were predicted by quantum‐chemical calculations as was the nature of bonding in the free Lewis acids and their mono‐ and dihydrates. Furthermore, the synthesis and structural diversity of hydroxido tris(pentafluoroethyl) gallates and one indate are presented. [ABSTRACT FROM AUTHOR]

We recently reported the potential of a new gallium compound, gallium acetylacetonate (GaAcAc) in combating osteoclastic bone resorption through inhibition of osteoclast differentiation and function. Herein, we focused on 3D-printed polylactic acid scaffolds that were loaded with GaAcAc and investigated the impact of scaffold pretreatment with polydopamine (PDA) or sodium hydroxide (NaOH). We observed a remarkable increase in scaffold hydrophilicity with PDA or NaOH pretreatment while biocompatibility and in vitro degradation were not affected. NaOH-pretreated scaffolds showed the highest amount of GaAcAc loading when compared to other scaffolds (p < 0.05). NaOH-pretreated scaffolds with GaAcAc loading showed effective reduction of osteoclast counts and size. The trend was supported by suppression of key osteoclast differentiation markers such as NFAT2, c-Fos, TRAF6, & TRAP. All GaAcAc-loaded scaffolds, regardless of surface pretreatment, were effective in inhibiting osteoclast function as evidenced by reduction in the number of resorptive pits in bovine cortical bone slices (p < 0.01). The suppression of osteoclast function according to the type of scaffold followed the ranking: GaAcAc loading without surface pretreatment > GaAcAc loading with NaOH pretreatment > GaAcAc loading with PDA pretreatment. Additional studies will be needed to fully elucidate the impact of surface pretreatment on the efficacy and safety of GaAcAc-loaded 3D-printed scaffolds. [ABSTRACT FROM AUTHOR]

Abstract The authors report a novel structure to improve the high‐frequency performance of nitrogen‐polar GaN deep‐recess high electron mobility transistors (HEMTs) wherein a timed plasma etch was used to tailor the profile of the gate dielectric. A favourable trade‐off between gate fringing capacitance and transconductance was established, resulting in an improved current gain cutoff frequency times gate length (ft·LG) figure of merit compared to standard Schottky‐gate and metal‐insulator‐semiconductor (MIS) HEMTs. The etched gate dielectric MISHEMT demonstrated a maximum ft·LG of 15.0 GHz·µm for an LG of 100 nm.

The authors report a novel structure to improve the high‐frequency performance of nitrogen‐polar GaN deep‐recess high electron mobility transistors (HEMTs) wherein a timed plasma etch was used to tailor the profile of the gate dielectric. A favourable trade‐off between gate fringing capacitance and transconductance was established, resulting in an improved current gain cutoff frequency times gate length (ft·LG) figure of merit compared to standard Schottky‐gate and metal‐insulator‐semiconductor (MIS) HEMTs. The etched gate dielectric MISHEMT demonstrated a maximum ft·LG of 15.0 GHz·µm for an LG of 100 nm. [ABSTRACT FROM AUTHOR]

The interface and bulk properties of ∼20 nm hafnium-silicon-oxide (HfSiOx) dielectric deposited by atomic layer deposition (ALD) on (001) β-Ga2O3 were investigated systematically using deep ultraviolet photo-assisted capacitance–voltage (C–V) and current–voltage (I–V) measurements. The ALD HfSiOx dielectric constant, bulk, and HfSiOx/Ga2O3 interface quality and breakdown field were determined, and the impact of post-deposition annealing (PDA) on these parameters was studied. PDA reduced near-interface traps resulting in a smaller hysteresis without changing the dielectric constant. An average trap density of 2.72 × 1012 and 1.06 × 1012 cm−2 eV−1 was measured on samples with PDA at 400 and 900 °C, respectively. In addition, a high dielectric constant of 9.28 and breakdown field as high as 8.7 MV/cm were achieved on these devices. [ABSTRACT FROM AUTHOR]

Professor Joseph "Joe" Greene taught me a great deal about research, leadership, and how to succeed. He was a mentor and a tireless advocate for me over the course of my career. This article summarizes some of the work that my research group carried out, inspired by Prof. Greene but not in direct collaboration with him. Three examples of these efforts are provided, epitaxial growth of Cu(In,Ga)Se2 (CIGS) on GaAs by sputter deposition, synthesis of Cu-Mo metastable alloys by sputter deposition, and recrystallization of CIGS deposited at high rates by treatment with metal halides. These works were carried out with many collaborators who are acknowledged in the description of the research carried out by them and in the references where full details can be found. [ABSTRACT FROM AUTHOR]

The introduction of a number of unsaturated fluorinated and chlorinated substituents onto gallium and indium was investigated. Gallate, [GaR4]−, and indate, [InR4]−, anions with trifluorovinyl (CF=CF2), 1‐chloro‐2,2‐difluorovinyl (CCl=CF2), (E)‐pentafluoropropen‐1‐yl (E‐CF=CFCF3), 3,3,3‐trifluoropropynyl (C≡C−CF3) and dichloromethyl (CHCl2) substituents were synthesized and isolated as the respective tetraphenylphosphonium salts. The respective gallate and indate salts were characterized by various methods, including NMR spectroscopy, mass spectrometry and X‐ray diffraction analysis. The generation of the respective organyllithium reagents, required for the syntheses of the gallate and indates, was performed starting from commercially available materials. This series of novel gallate and indate salts extends the chemistry of electron withdrawing groups to gallium and indium compounds. [ABSTRACT FROM AUTHOR]

The structure of µ-oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc) and the structure of a second modification of chloro(phthalocyaninato)gallium(III) (ClGaPc) has been determined by single-crystal X-ray analysis. Sublimation of the respective compounds led to single crystals suitable for an X-ray study. Both compounds crystallize in the triclinic space group P 1 ¯ , with a unit cell for ClGaPc a = 13.770 Å, b = 13.770 Å, c = 14.039 Å, α = 98.32°, β = 108.64°, γ = 90.01°, containing four disordered molecules (Z = 4). The unit cell of the dimeric PcGaOGaPc contains one molecule, with half a molecule as an asymmetric moiety (Z = 2) and a = 7.848 Å, b = 12.529 Å, c = 12.720 Å, α = 91.03°, β = 94.94°, γ = 89.98°. The Ga atoms for the two ClGaPc molecules are placed 0.44 Å above the plane formed by the respective isoindole nitrogen N1 to N4. The two rings of the asymmetric unit (molecule 1 and 2) are arranged in parallel, with ca. 3.4 Å distance within the unit cell. The Ga-Cl bond distances are ca. 2.20 Å for the two molecules. The gallium of PcGaOGaPc is placed 0.49 Å above the respective isoindole nitrogen plane and the Ga-O bond amounts to 1.734 Å. [ABSTRACT FROM AUTHOR]

Abstract This paper presents simulation and measurement results of a 2–4 GHz octave bandwidth interference suppression circuit. The circuit accomplishes the function of a tunable frequency notch through an interferometer architecture. The relative delay in the interferometer paths is varied with GaN monolithic microwave integrated circuit tunable delay lines. The delay is adjusted by varying the drain voltage of cold‐FET connected high electron mobility transistors acting as varactors. Two types of periodically‐loaded delay lines are compared: a uniform and a tapered design. A simple theoretical study, relating the delays and amplitudes in the interferometer circuit branches, is developed to inform the design. Two interference suppression hybrid circuits are implemented, and measurements demonstrate a 25–40 dB notch across the 2.24–4 GHz range for the uniform delay line, and 2.32–4.13 GHz for the tapered design. The return loss for both designs remains below 10 dB. Measurements with two tones spaced 0.5 and 1 GHz for varying tone power are performed to quantify suppression. The circuit can handle an input power of 37 dBm and maintains performance with two simultaneous 25 dBm tones spaced 0.5 GHz apart. Linearity is characterised with 10 MHz two‐tone measurements, and the circuit demonstrates a 3rd‐order intercept input power larger than 30 dBm for control biases above −12 V.

High crystalline quality epitaxial films of orthorhombic gallium oxide ε(κ)-Ga2O3 with a thickness of more 20 μm have been grown for the first time using halide vapor phase epitaxy. Sapphire wafers with preliminarily deposited GaN layers were used as substrates. The properties of the produced films are studied by X-ray diffraction and electron microscopy. The results are considered an important step towards obtaining thick layers and quasi-bulk ε(κ)-Ga2O3 crystals for practical applications in electronics and sensor technology. [ABSTRACT FROM AUTHOR]

Terminal aluminium and gallium imides of the type K[(NON)M(NR)], bearing heteroatom substituents at R, have been synthesised via reactions of anionic aluminium(I) and gallium(I) reagents with silyl and boryl azides (NON=4,5‐bis(2,6‐diisopropyl‐anilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethyl‐xanthene). These systems vary significantly in their lability in solution: the N(SiiPr3) and N(Boryl) complexes are very labile, on account of the high basicity at nitrogen. Phenylsilylimido derivatives provide greater stabilization through the π‐acceptor capabilities of the SiR3 group. K[(NON)AlN(SitBuPh2)] offers a workable compromise between stability and solubility, and has been completely characterized by spectroscopic, analytical and crystallographic methods. The silylimide species examined feature minimal π‐bonding between the imide ligand and aluminium/gallium, with the HOMO and HOMO‐1 orbitals effectively comprising orthogonal lone pairs centred at N. Reactivity‐wise, both aluminium and gallium silylimides can act as viable sources of nitride, [N]3−, with systems derived from either metal reacting with CO to afford cyanide complexes. By contrast, only the gallium system K[(NON)Ga{N(SiPh3)}] is capable of effecting a similar transformation with N2O to yield azide, N3−, via formal oxide/nitride metathesis. The aluminium systems instead generate RN3 via transfer of the imide fragment [RN]2−. [ABSTRACT FROM AUTHOR]

In this paper, an n–p–n structure based on a β-Ga2O3/NiO/β-Ga2O3 junction was fabricated. The device based on the β-Ga2O3/NiO/β-Ga2O3 structure, as an ultraviolet (UV) photodetector, was compared with a p–n diode based on a NiO/β-Ga2O3 structure, where it showed rectification and 10 times greater responsivity and amplified the photocurrent. The reverse current increased in proportion to the 1.5 power of UV light intensity. The photocurrent amplification was related to the accumulation of holes in the NiO layer given by the heterobarrier for holes from the NiO layer to the β-Ga2O3 layer. Moreover, the device could respond to an optical pulse of less than a few microseconds. [ABSTRACT FROM AUTHOR]

Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics. [ABSTRACT FROM AUTHOR]

A general pathway towards NHC (NHC=N‐heterocyclic carbene)‐stabilized galliummonotriflates NHC ⋅ GaH2(OTf) (NHC=IDipp, 1 a; IPr2Me2, 1 b; IMes, 1 c; IDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐ylidene, IPr2Me2=1,3‐bis‐(diisopropyl)‐4,5‐dimethyl‐imidazolin‐2‐ylidene, IMes=1,3‐bis(2,4,6‐trimethylphenyl)‐imidazolin‐2‐ylidene) is reported. Quantum chemical calculations give detailed insight into the underlying reaction pathway. The obtained NHC ⋅ GaH2(OTf) compounds were employed in reactions with donor‐stabilized pnictogenylboranes to synthesize the elusive cationic parent 13/15/13 chain compounds [IDipp ⋅ GaH2ER2E'H2 ⋅ D][OTf] (3 a: D=IDipp, E=P, E'=B, R=H; 3 b: D=NMe3, E=P, E'=B, R=H, 3 c: D=NMe3, E=P, E'=B, R=Ph, 3 d: D=IDipp, E=P, E'=Ga, R=H). Supporting computational studies highlight the electronic features of the products. [ABSTRACT FROM AUTHOR]

A combination of Ga(I) centers as important building blocks and scaffolds containing N-heterocyclic imines gives new insights into low-valent Ga chemistry. In this study, a mixture of LDipNLi (LDip = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene), tBuOK, and Cp*Ga (Cp* = pentamethylcyclopentadienyl) in toluene afforded [LDipN-Ga]2 (1) via salt metathesis. X-ray structure analysis of 1 revealed a four-membered Ga2N2 ring, and DFT studies indicated the presence of a lone pair at each Ga center. In addition, compound 1 demonstrated diverse reactivities towards methyl trifluoromethanesulfonate, diphenyl disulfide, 9,10-phenanthrenequinone, and ECl2 (E = Ge or Sn). [ABSTRACT FROM AUTHOR]

Beta gallium oxide (β-Ga2O3) shows significant promise in high-temperature, high-power, and sensing electronics applications. However, long-term stable metallization layers for Ohmic contacts at high temperatures present unique thermodynamic challenges. The current most common Ohmic contact design based on 20 nm of Ti has been repeatedly demonstrated to fail at even moderately elevated temperatures (300–400 °C) due to a combination of nonstoichiometric Ti/Ga2O3 interfacial reactions and kinetically favored Ti diffusion processes. Here, we demonstrate stable Ohmic contacts for Ga2O3 devices operating up to 500–600 °C using ultrathin Ti layers with a self-limiting interfacial reaction. The ultrathin Ti layer in the 5 nm Ti/100 nm Au contact stack is designed to fully oxidize while forming an Ohmic contact, thereby limiting both thermodynamic and kinetic instability. This novel contact design strategy results in an epitaxial conductive anatase titanium oxide interface layer that enables low-resistance Ohmic contacts that are stable both under long-term continuous operation (>500 h) at 600 °C in vacuum (≤10−4 Torr), as well as after repeated thermal cycling (15 times) between room temperature and 550 °C in flowing N2. This stable Ohmic contact design will accelerate the development of high-temperature devices by enabling research focus to shift toward rectifying interfaces and other interfacial layers. [ABSTRACT FROM AUTHOR]

This paper presents simulation and measurement results of a 2–4 GHz octave bandwidth interference suppression circuit. The circuit accomplishes the function of a tunable frequency notch through an interferometer architecture. The relative delay in the interferometer paths is varied with GaN monolithic microwave integrated circuit tunable delay lines. The delay is adjusted by varying the drain voltage of cold‐FET connected high electron mobility transistors acting as varactors. Two types of periodically‐loaded delay lines are compared: a uniform and a tapered design. A simple theoretical study, relating the delays and amplitudes in the interferometer circuit branches, is developed to inform the design. Two interference suppression hybrid circuits are implemented, and measurements demonstrate a 25–40 dB notch across the 2.24–4 GHz range for the uniform delay line, and 2.32–4.13 GHz for the tapered design. The return loss for both designs remains below 10 dB. Measurements with two tones spaced 0.5 and 1 GHz for varying tone power are performed to quantify suppression. The circuit can handle an input power of 37 dBm and maintains performance with two simultaneous 25 dBm tones spaced 0.5 GHz apart. Linearity is characterised with 10 MHz two‐tone measurements, and the circuit demonstrates a 3rd‐order intercept input power larger than 30 dBm for control biases above −12 V. [ABSTRACT FROM AUTHOR]

The N-Heterocyclic Carbene (NHC) alane and gallane adducts (NHC)·Cp*AlH2 (NHC = Me2ImMe5, iPr2ImMe6, Dipp2Im 7) and (NHC)·Cp*GaH2 (NHC = Me2ImMe8, iPr2ImMe9, Dipp2Im 10; R2Im = 1,3-di-organyl-imidazolin-2-ylidene; Dipp = 2,6 diisopropylphenyl; Me2ImMe = 1,3,4,5-tetra-methyl-imidazolin-2-ylidene; Cp* = C5Me5) were prepared either via the reaction of (AlH2Cp*)31 with the NHC or by the treatment of (NHC)·GaH2I (NHC = Me2ImMe2, iPr2ImMe3, Dipp2Im 4) with KCp*. The reaction of (AlH2Cp*)31 with the backbone saturated NHC Dipp2ImH led to NHC ring expansion instead with the formation of (RER-Dipp2ImHH2)AlCp* 12. Heating solutions of the gallium compounds 8–10 triggered reductive elimination of Cp*H and afforded Cp*GaI16. The reaction of the alane adduct (Me2ImMe)·Cp*AlH25 with cAACMe led to the insertion of cAACMe into the Al–H bond with the formation of the compound rac-(Me2ImMe)·AlHCp*(cAACMeH) rac -14. Heating a solution of rac -14 led to irreversible isomerisation with the formation of (Me2ImMe)·AlHCp*(cAACMeH) meso- 14. The alane adducts (iPr2ImMe)·Cp*AlH26 and (Dipp2Im)·Cp*AlH27 react with cAACMe with the release of the NHC and formation of the exceptionally stable oxidative addition product (cAACMeH)AlHCp* 15. Reactions of the gallane adducts 8–10 with cAACMe led to reductive elimination of cAACMe–H2 and the formation of Cp*GaI16. [ABSTRACT FROM AUTHOR]

In the research, to describe the spinodal decomposition of A³B5 semiconductor solid solutions, in which the substitution of the main components occurs simultaneously in each of the sublattices of the sphalerite crystal structure, the Cahn-Hilliard concepts are extended. The resulting system of differential equations is applied to describe the effect of composition modulation in GaxIn1--xPyAs1--y solid solutions grown on InP substrates. In this case, the elastic deformation energy of a thin layer of GaxIn1--xPyAs1--y solid solution is calculated on the assumption of its coherent conjugation with a massive InP substrate. The excess mixing energy of the components in the solid phase is evaluated in accordance with the simple solution model. The temperature-concentration ranges, in which the conditions for the occurrence of an oscillatory mode of relaxation of the supersaturated metastable state of the solid phase are realized, are found by analyzing phase portraits of the system. The performed analysis shows that the effect of modulation of the material composition is connected with the resonance of total entire excess energy and elastic energy. The parameters of the oscillatory process are compared with data on the effect of composition stabilization, which is experimentally observed in the growth of elastically stressed heterostructures GaxIn1--xPyAs1--y -- InP substrate. [ABSTRACT FROM AUTHOR]

The structure of µ-oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc) and the structure of a second modification of chloro(phthalocyaninato)gallium(III) (ClGaPc) has been determined by single-crystal X-ray analysis. Sublimation of the respective compounds led to single crystals suitable for an X-ray study. Both compounds crystallize in the triclinic space group P1¯, with a unit cell for ClGaPc a = 13.770 Å, b = 13.770 Å, c = 14.039 Å, α = 98.32°, β = 108.64°, γ = 90.01°, containing four disordered molecules (Z = 4). The unit cell of the dimeric PcGaOGaPc contains one molecule, with half a molecule as an asymmetric moiety (Z = 2) and a = 7.848 Å, b = 12.529 Å, c = 12.720 Å, α = 91.03°, β = 94.94°, γ = 89.98°. The Ga atoms for the two ClGaPc molecules are placed 0.44 Å above the plane formed by the respective isoindole nitrogen N1 to N4. The two rings of the asymmetric unit (molecule 1 and 2) are arranged in parallel, with ca. 3.4 Å distance within the unit cell. The Ga-Cl bond distances are ca. 2.20 Å for the two molecules. The gallium of PcGaOGaPc is placed 0.49 Å above the respective isoindole nitrogen plane and the Ga-O bond amounts to 1.734 Å.

Stoichiometric gallium oxide sulfide Ga2(O1 − xSx)3 thin-film alloys were synthesized by pulsed-laser deposition with x ≤ 0.35. All deposited Ga2(O1 − xSx)3 films were found to be amorphous. Despite the amorphous structure, the films have a well-defined, room-temperature optical bandgap tunable from 5.0 eV down to 3.0 eV. The optical absorption data are interpreted using a modified valence-band anticrossing model that is applicable for highly mismatched alloys. The model provides a quantitative method to more accurately determine the bandgap as well as an insight into how the band edges are changing with composition. The observed large reduction in energy bandgap with a small sulfur ratio arises from the anticrossing interaction between the valence band of Ga2O3 and the localized sulfur level at 1.0 eV above the Ga2O3 valence-band maximum. [ABSTRACT FROM AUTHOR]

Here, we perform a theoretical investigation of the impact of film thickness and incident angle on the surface plasmon resonance spectra for annealed and postannealed Ga-doped ZnO (ZnO:Ga) in a 3-phase Kretschmann configuration. A detailed comparative study has been performed to determine the optimum configuration to be utilized for sensing applications. Though both films are found to support plasmonic excitation for thickness below 200 nm, detection accuracy and sensitivity calculations from the resonance plots simulated in the MATLAB environment reveal that the preference of one over the other should be in accordance with the concerned application. [ABSTRACT FROM AUTHOR]

Recently, nanoporous (NP) GaN has emerged as a promising photonic material in the III-N family. Due to its attractive properties, such as its large refractive index contrast and perfect lattice matching with GaN, as well as its good electrical conductivity, photonic components and devices involving NP GaN have been successfully demonstrated. However, further development of high-performance NP GaN based electrically injected devices, such as vertical-cavity surface-emitting lasers (VCSELs) and edge emitting lasers, requires efficient heat dissipation. Therefore, in this paper, we study thermal conductivity (TC) of NP GaN, especially when incorporated into a practical distributed Bragg reflector (DBR) in a VCSEL device. Through an effective medium model, we study the theoretical effect of NP GaN morphological properties over its TC. We then experimentally measure the TC of NP GaN, with different porosities and pore wall thicknesses, which shows a high agreement with the theoretical model. We also fabricate actual NP GaN DBRs and study the large tunability and interdependence among their TC (1–24 W/m K), refractive index (0.1–1.0), and electrical conductivity (100–2000 S/m) compared to other conventional DBRs. Finally, we perform a finite-element simulation of the heat dissipation within NP GaN-VCSELs, revealing their superior thermal dissipation compared to dielectric DBR based VCSELs. In this regard, this study lays the foundation for nanoscale thermal engineering of NP GaN optoelectronic and photonic devices and paves the way for their successful commercialization. [ABSTRACT FROM AUTHOR]

Persistent photocapacitance (PPC) was observed in β-(Al0.14Ga0.84)2O3/n+Ga2O3 heterojunctions at low temperatures. The effect is seen in capacitance-frequency measurements under illumination and in admittance spectra after illumination. In the latter case, the capacitance versus frequency curve after illumination returned to its dark values only at temperatures between 225 and 275 K. Prominent hole-trap-like peaks in optical deep level transient spectroscopy (ODLTS) near 130 K were attributed to quenching with temperature of the PPC effect. The phenomena were assigned to electrons being excited from deep traps in the (Al0.14Ga0.86)2O3 barrier into the two-dimensional electron gas (2DEG) in the Ga2O3 substrate. The reverse process then involves excitation of non-equilibrium electrons in the 2DEG back into the ternary barrier layer and subsequent re-capture by the host deep traps. The effective barrier height for this recovery process was ∼0.2 eV, as estimated from ODLTS measurements. The spectral dependence of the effect suggests the presence of deep traps with optical ionization thresholds near 1 eV and ∼2.3 eV. The shift of the threshold voltage necessary to deplete the 2DEG as a function of the photon energy during illumination at room temperature indicates that the most prominent centers in the barrier have an optical ionization energy near 2.3 eV and a sheet density of ∼1012 cm−2. In microcathodoluminescence (MCL) spectra of the heterojunction, a blue shift by 0.2 eV of the MCL band near 3.1 eV dominant in the substrate and the emergence of a weak MCL peak near 4.8 eV were observed. Electron beam induced current measurements point to the presence of small local areas where the 2DEG formation is handicapped due to Al composition variations or to defects. [ABSTRACT FROM AUTHOR]

The CuPt ordering of the group III elements in GaxIn1-xP (x ≃ 0.5) has been observed to vary during growth by metalorganic vapor-phase epitaxy of InAs quantum dots capped with GaAs in a GaInP matrix. While ordering is not affected by the insertion of a GaAs layer, the growth of InAs quantum dots capped with GaAs results in ordered, partially ordered, or fully disordered GaInP. We show that the degree of ordering depends on the deposition time of the InAs quantum dots and on the thickness of the GaAs capping layer. Our results indicate that disordered GaInP occurs in the presence of excess indium at the growth surface, which results from the growth of strained InAs quantum dots. Ordering resumes when the excess indium is consumed. Cathodoluminescence, scanning transmission electron microscopy, and atomic force microscopy are used in this study to correlate the electronic properties and the microstructure of the thin films. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) and infrared absorption are used to detect Ir4+ ions in β-Ga2O3 crystals. Mg and Fe doped crystals are investigated, and concentrations of Ir4+ ions greater than 1 × 1018 cm−3 are observed. The source of the unintentional deep iridium donors is the crucible used to grow the crystal. In the Mg-doped crystals, the Ir4+ ions provide compensation for the singly ionized Mg acceptors and thus contribute to the difficulties in producing p-type behavior. The Ir4+ ions replace Ga3+ ions at the Ga(2) sites, with the six oxygen neighbors forming a distorted octahedron. A large spin-orbit coupling causes these Ir4+ ions to have a low-spin (5d5, S = 1/2) ground state. The EPR spectrum consists of one broad line with a significant angular dependence. Principal values of the g matrix are 2.662, 1.815, and 0.541 (with principal axes near the crystal a, b, and c directions, respectively). Ionizing radiation at 77 K decreases the Ir4+ EPR signal in Mg-doped crystals and increases the signal in Fe-doped crystals. In addition to the EPR spectrum, the Ir4+ ions have an infrared absorption band representing a d-d transition within the t2g orbitals. At room temperature, this band peaks near 5153 cm−1 (1.94 μm) and has a width of 17 cm−1. The band is highly polarized: its intensity is maximum when the electric field E is parallel to the b direction in the crystal and is nearly zero when E is along the c direction. [ABSTRACT FROM AUTHOR]

[Display omitted] The reactions of [LGa–GaL] (L = dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) with ammonia and pyrrolidine in toluene lead to the formation of adducts [L(NH 3)Ga–Ga(NH 3)L], [L(HNC 4 H 8)Ga–GaL] and [L(HNC 4 H 8)Ga–Ga(HNC 4 H 8)L], respectively. In contrast, the reaction between crystalline digallane and an excess of pyrrolidine leads to the formation of compound [LGa(NC 4 H 8)(HNC 4 H 8)]. The complex [LGa(C 5 H 5 N)(μ-O)Ga(C 5 H 5 N)L] was obtain from reaction of digallane with N 2 O in the presence of pyridine. [ABSTRACT FROM AUTHOR]

We have investigated the performance characteristics of a III-nitride high electron mobility transistor (HEMT) on different substrates. It exhibits a negative threshold voltage (depletion mode) for a HEMT grown on silicon (Si), silicon carbide (SiC), and sapphire substrates, whereas it shows a positive threshold voltage (enhancement mode) when grown on beta-gallium oxide (β-Ga2O3). Compared to Si, SiC, and sapphire, β-Ga2O3 improves different parameters, such as off-state leakage characteristics, subthreshold voltage, breakdown voltage (VBR), and radio frequency (RF) performance. In addition, it shows breakdown voltage characteristics of 4 V, 11 V, 94 V, and 108 V for a HEMT grown on Si, sapphire, SiC, and β-Ga2O3 , respectively. It also exhibits cut-off frequencies of 122 GHz, 342 GHz, 380 GHz, and 420 GHz for HEMT using Si, sapphire, SiC, and β-Ga2O3 substrates, respectively. Generally, HEMTs suffer from a trade-off between breakdown voltage and frequency characteristics. However, the proposed III-nitride HEMT developed on β-Ga2O3 demonstrated an improved breakdown voltage without affecting its high-frequency characteristics. This achievement is mainly because of a better lattice match between the buffer material and the substrate. This research aims to provide a comprehensive understanding of a III-nitride nano-HEMT developed on a β-Ga2O3 substrate in order to aid future research in this cutting-edge technology. [ABSTRACT FROM AUTHOR]

The anodic dissolution of aluminum in the KOH ethanol solutions is considered. It is shown that an addition of gallium and indium compounds to the 2 M KOH solution in 96% ethanol leads to an abrupt increase in the anodic dissolution current of aluminum near the open-circuit potential and its shift by 300 mV toward negative values. The discharge galvanostatic curves in the solutions with the additives of gallium and indium compounds contain a flat discharge plateau at the current densities up to 4 mA/cm2. The hydrogen evolution rate in a number of KOH ethanol solutions is measured. [ABSTRACT FROM AUTHOR]

The structural and optical properties of gold-nucleated GaN grown on Au/Si (100) and Au/c-sapphire were enhanced using a post-annealing procedure at 950 °C, under an ammonia environment. Before the GaN chemical vapor deposition process, the formation of Au droplets was promoted by an in situ dewetting mechanism, applying a heat treatment to the Au-covered c-sapphire, and silicon (100) substrates. The size and morphology of the Au sites were characterized by atomic force microscopy. According to the X-ray diffraction and Raman spectroscopy results, crystalline enhancement of the GaN wurtzite structure was obtained in both, the Au/sapphire and Au/Si (100). SEM micrographs reveal the presence of GaN micro-whiskers in as-grown samples. After the treatment herein proposed, morphology was modified as shown in the plan-view and cross section results. The GaN near-band emission at 3.34 eV was boosted by the localized surface plasmon effect. Additionally, the GaN bandgap energy was estimated by diffuse reflectance measurements and by the modified Kubelka–Munk function, as 3.35 eV. [ABSTRACT FROM AUTHOR]

Background: Nontuberculous mycobacteria (NTM) are ubiquitous. NTM can affect different organs and may cause disseminated diseases, but the pulmonary form is the most common form. Pulmonary NTM is commonly seen in patients with underlying diseases. Pulmonary Mycobacterium avium complex (MAC) is the most common NTM disease and M. abscessus (MAB) is the most challenging to treat. This review is prepared with the following objectives: (a) to evaluate new methods available for the diagnosis of pulmonary MAC or MAB, (b) to assess advances in developing new therapeutics and their impact on treatment of pulmonary MAC or MAB, and (c) to evaluate the prospects of preventive strategies including vaccines against pulmonary MAC or MAB. Methods: A literature search was conducted using PubMed/MEDLINE and multiple search terms. The search was restricted to the English language and human studies. The database query resulted in a total of 197 publications. After the title and abstract review, 64 articles were included in this analysis. Results: The guidelines by the American Thoracic Society (ATS), European Respiratory Society (ERS), European Society of Clinical Microbiology and Infectious Diseases (ESCMID), and Infectious Diseases Society of America (IDSA) are widely applicable. The guidelines are based on expert opinion and there may be a need to broaden criteria to include those with underlying lung diseases who may not fulfill some of the criteria as 'probable cases' for better follow up and management. Some cases with only one culture-positive sputum sample or suggestive histology without a positive culture may benefit from new methods of confirming NTM infection. Amikacin liposomal inhalation suspension (ALIS), gallium containing compounds and immunotherapies will have potential in the management of pulmonary MAC and MAB. Conclusions: the prevalence of pulmonary NTM is increasing. The efforts to optimize diagnosis and treatment of pulmonary NTM are encouraging. There is still a need to develop new diagnostics and therapeutics. [ABSTRACT FROM AUTHOR]

Abstract The operation of parallel‐connected servo drives has the advantages of increasing the torque (hence the power) capacity, reliability, redundancy and modularity. However, smaller discrepancies of the system clocks of the independent microcontrollers, asynchronous pulse width modulation (PWM) carrier signals and hardware differences can make the output voltages of the parallel modules non‐identical, which results in circulating currents. These circulating currents limit the parallel operation, introduce additional power dissipation, cause unbalanced power distribution and degrade the control performance. To eliminate the circulating currents separated DC supplies, coupled inductors (CIs), PWM techniques, modified control techniques etc. are proposed in the literature. In this study, a fault‐tolerant parallel‐connected gallium nitride enhancement‐mode high electron mobility transistor voltage source inverter‐based servo drive scheme that eliminates the need for CIs and separate DC supplies and also enables the use of a standard proportional‐integral current control and a standard space vector PWM approach is proposed and tested. To evaluate the performances of the proposed scheme, up to six servo drives (limit‐6 × 7 Arms) are connected in parallel and tested under various conditions with a 24 V permanent magnet synchronous motor (nominal‐61.9 Arms). The results show that the parallel operation not only increases the torque capacity of the system but also increases modularity, flexibility, reliability and also redundancy.

Pulsed sputter deposition has been demonstrated to be a viable process for the growth of high quality GaN and InGaN/GaN LEDs. It enables the fabrication of nitride LEDs with a red emission wavelength at large areas. In this study, we explore details on the epitaxial sputter deposition of GaN with a particular emphasis on ion damage. By changing the argon to nitrogen ratio, we adjust the growth mode from island to layer growth. TEM revealed speckles in the epitaxial GaN, which could be identified as isolated basal stacking faults, acting as non-radiative recombination centers. Using Monte Carlo methods, we modeled the energies of backscattered and sputtered atoms in order to get information on the ion damage mechanisms. Considering the collisions on the way from the target to the substrate, we found energetic nitrogen to induce the speckles. A shielding mechanism based on metallic gallium has been identified, leading to the strongly increased luminescence quality in comparison to the non-shielded material. [ABSTRACT FROM AUTHOR]

We addressed the issue of atomic ordering in a series of In-rich In x Ga 1 − x N epilayers grown on a GaN/AlN/sapphire(0001) epitaxial template by quantitatively measuring the Ga-cation coordination in the second atomic shell of Ga. We used Diffraction Anomalous Fine Structure Spectroscopy (DAFS) at the Ga K-edge to select the signal coming from the Ga atoms in the epilayer and eliminate any contribution from the buffer layer. DAFS measurements were also performed on hydrogenated epilayers in order to investigate the possible formation of Ga-H complexes. We find that deviation from cation random distribution in the form of Ga clustering is present in both untreated and hydrogenated samples and that in the latter ones the second atomic shell around Ga is modified, suggesting an additional perturbation of the cation sublattice related to hydrogen. However, comparing the present results with In K-edge x-ray absorption spectra previously reported, we conclude that the formation of Ga-H complexes vs. In-H ones is unlikely. Cation clustering has to be anyway taken into account as a possible channel playing in the determination of the optical bandgap of these technology-oriented semiconductors. [ABSTRACT FROM AUTHOR]

The thermal conductivity of GaN crystals grown by different techniques is analyzed using the 3ω method in the temperature range of 30 K to 295 K. GaN wafers grown by the ammonothermal method show a significant variation in thermal conductivity at room temperature with values ranging between 164 W m−1 K−1 and 196 W m−1 K−1. GaN crystals produced with the sodium flux and hydride vapor phase epitaxy methods show results of 211 W m−1 K−1 and 224 W m−1 K−1, respectively, at room temperature. Analysis using secondary ion mass spectrometry indicates varying amounts of impurities between the respective crystals and explains the behavior of thermal conductivity trends in the samples. The observed difference between thermal conductivity curves suggests that scattering of phonons at point defects dominates the thermal conductivity of GaN within the investigated temperature range. Deviations of model curves from thermal conductivity measurements and disparities between modelled characteristic lengths and actual sample thicknesses indicate that phonon resonances are active in GaN. [ABSTRACT FROM AUTHOR]

Gallium telluride is a layered material with high photoresponse and is very promising for applications in optoelectronic devices such as photovoltaic cells or radiation detectors. We analyze how the properties of thin films of this material scale with its thickness and also study two other proposed materials with the same crystalline structure whose room-temperature stability we verify. We show that electronic band gaps up to 2.16 eV can be obtained by stacking up and/or applying perpendicular electric field to these III-Te monolayers. This form of band gap engineering may be promising for several technological applications. [ABSTRACT FROM AUTHOR]

The intermetallic gallium compounds RE2Co2Ga with different rare earths (RE = Dy, Ho, Er, and Tm) were synthesized, and their crystal structure, microstructure, magnetic, and cryogenic magneto-caloric performances were investigated. The RE2Co2Ga compounds crystallize with an ordered orthorhombic W2B2Co-type structure (space group Immm). All the RE2Co2Ga compounds undergo ferromagnetic (FM) ordering (second-order) from a paramagnetic to FM transition which induces reversible magneto-caloric effects (MCE). The Curie temperatures (TC) in RE2Co2Ga compounds are determined to be 55.0, 38.5, 25.5, and 11.6 K for RE = Dy, Ho, Er, and Tm, respectively, which fulfill the de Gennes scaling. The RE2Co2Ga compounds show relatively small MCE (i.e., −ΔSM, isothermal magnetic entropy change) around their own phase transition temperatures, and the maximal values of −ΔSM are 7.5, 14.6, 11.2, and 13.2 J/kg K in the field change (ΔH) of 7 T for RE = Dy, Ho, Er, and Tm, respectively. Accordingly, the values of the relative cooling power are 212, 335, 304, and 239 J/kg, respectively. [ABSTRACT FROM AUTHOR]

Although they have been widely used as models for oxide surfaces, the deprotonation behaviors of the Keggin-ions (MeAl127+) and typical oxide surfaces are very different. On Keggin-ions, the deprotonation occurs over a very narrow pH range at odds with the broad charging curve of larger oxide surfaces. Depending on the Me concentration, the deprotonation curve levels off sooner (high Me concentration) or later (for low Me concentration). The leveling off shows the onset of aggregation before which the Keggin-ions are present as individual units. We show that the atypical titration data previously observed for some GaAl12 solutions in comparison to the originally reported data can be explained by the presence of Ga2Al11 ions. The pKa value of aquo-groups bound to octahedral Ga was determined from ab initio molecular dynamics simulations relative to the pure GaAl12 ions. Using these results within a surface complexation model, the onset of deprotonation of the crude solution is surprisingly well predicted and the ratio between the different species is estimated to be in the proportion 20 (Ga2Al11) : 20 (Al13) : 60 (GaAl12). [ABSTRACT FROM AUTHOR]

Electroluminescence (EL) measurements were carried out to investigate the irradiation effects of 1.0 MeV electrons on the current density-voltage (J-V) characteristics of the GaInP top cell and GaAs middle cell of GaInP/GaAs/Ge triple-junction solar cells at injection current densities ranging from 2.5 mA/cm2 to 30 mA/cm2. By utilizing the optoelectronic reciprocity relation between the EL and external quantum efficiency, the dark J-V characteristics of the two subcells, as well as the short circuit current density and the open circuit voltage, were derived. It is shown that the short circuit current density and the open circuit voltage of the top cell and the middle cell both degrade with the increasing fluence, but that of the middle cell degrades more than the top cell at the same fluence. Meanwhile, the current-limiting cell changes from GaInP top cell to the GaAs middle cell. The GaAs middle cell contributes to more loss in voltage of the 3 J solar cell. [ABSTRACT FROM AUTHOR]

The critical behaviors of polycrystalline Ni2MnGa and Ni2Mn0.85Cu0.15Ga have been examined through high-resolution bulk magnetization measurements. The critical exponents, β and γ, were derived from modified Arrott plots using the Kouvel-Fisher method. The values of the extracted critical exponents satisfied the scaling equation of state and associated exponent relations, indicating self-consistency of the extracted values. In Ni2MnGa, the critical exponents (β = 0.401 ± 0.003, γ = 1.27 ± 0.02) indicate a deviation from the 3D-Heisenberg values toward the mean-field values, likely due to the presence of long-range Ruderman-Kittel-Kasuya-Yosida interactions. However, the critical exponents of Ni2Mn0.85Cu0.15Ga (β = 0.389 ± 0.004, γ = 1.39 ± 0.02) are closer to the 3D-Heisenberg values. This indicates a weakening of the long-range exchange interactions due to the substitution of Cu in the Mn site. [ABSTRACT FROM AUTHOR]

The spatial distribution of electron-hole pair generation in β-Ga2O3 as a function of scanning electron microscope (SEM) beam energy has been calculated by a Monte Carlo method. This spatial distribution is then used to obtain the diffusion length of charge carriers in high-quality epitaxial Ga2O3 films from the dependence of the electron beam induced current (EBIC) collection efficiency on the accelerating voltage of a SEM. The experimental results show, contrary to earlier theory, that holes are mobile in β-Ga2O3 and to a large extent determine the diffusion length of charge carriers. Diffusion lengths in the range 350–400 nm are determined for the as-grown Ga2O3, while processes like exposing the samples to proton irradiation essentially halve this value, showing the role of point defects in controlling minority carrier transport. The pitfalls related to using other popular EBIC-based methods assuming a point-like excitation function are demonstrated. Since the point defect type and the concentration in currently available Ga2O3 are dependent on the growth method and the doping concentration, accurate methods of diffusion length determination are critical to obtain quantitative comparisons of material quality. [ABSTRACT FROM AUTHOR]

Theoretically and experimentally evaluated optoelectronic properties of GZO (Ga-doped zinc oxide) were correlated in the present article. Density functional theory and Hubbard U (DFT + Ud + Up) first-principle calculations were used for the theoretical study. The pulsed laser deposition technique was used to fabricate GZO thin films on p-GaN, Al2O3, and p-Si substrates. X-ray diffraction graphs show single crystal growth of GZO thin films with (002) preferred crystallographic orientation. The chemical composition was studied via energy dispersive X-ray spectroscopy, and no other unwanted impurity-related peaks were found, which indicated the impurity-free thin film growth of GZO. Field emission scanning electron microscopic micrographs revealed noodle-, seed-, and granular-like structures of GZO/GaN, GZO/Al2O3, and GZO/Si, respectively. Uniform growth of GZO/GaN was found due to fewer mismatches between ZnO and GaN (0.09%). Hall effect measurements in the van der Pauw configuration were used to check electrical properties. The highest mobility (53 cm2/Vs) with a high carrier concentration was found with low laser shots (1800). A 5-fold photoluminescence enhancement in the noodle-like structure of GZO/GaN compared with GZO/Al2O3 and GZO/Si was detected. This points toward shape-driven optical properties because the noodle-like structure is more favorable for optical enhancements in GZO thin films. Theoretical (3.539 eV) and experimental (3.54 eV) values of the band-gap were also found to be comparable. Moreover, the lowest resistivity (3.5 × 10−4 Ωcm) with 80% transmittance is evidence that GZO is a successful alternate of ITO. [ABSTRACT FROM AUTHOR]

We establish phase equilibria in the Eu–Zn–Ga ternary system for a partial isothermal section within the range of europium concentrations 0–33.3 at.% at 400°C. The X-ray powder diffraction analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy are used to identify the phases and investigate the crystal structures and compositions of the analyzed materials. The phase equilibria of the analyzed Eu–Zn–Ga system at 400°C are characterized by the formation of four solid solutions, gallium solubility in EuZn13, EuZn11, and EuZn5 and zinc solubility in EuGa4, as well as of one continuous EuZn2–EuGa2 solid solution, and the existence of a ternary intermetallic compound, EuZnx Ga3 – x, x = 0.15. This new compound crystallizes in the CeNiSi2 structural type (space group Cmcm) with a = 4.2900(6) Å, b = 18.405(2) Å, and c = 4.3836(7) Å. The analyzed partial isothermal section has eight ternary phase fields at 400°C. [ABSTRACT FROM AUTHOR]

Abstract This work presents a gallium nitride (GaN) high electron mobility transistor (HEMT)–based cascaded multistage power amplifier (MPA) in class‐AB for L‐band radar applications. The purpose of this endeavour is to develop an MPA using GaN HEMT devices to achieve optimised parameters such as high gain, high power, better efficiency, and linearity in a compact size. In an MPA design with multiple stages, oscillations are common owing to unwanted high gain at the lower frequency range. To overcome this issue, we introduced interstage harmonic termination networks as a novel approach to suppress high gain at low frequencies, which are prone to oscillations. The proposed cascaded MPA provides the maximum radio‐frequency output power of 89 W and a power gain of 52 dB with an associated power‐added efficiency of 51%. Second and third harmonic levels are −32.5 and −37 dBc, respectively. Two‐tone measurements are performed with a frequency separation of 10 MHz, and an intermodulation level of less than −33 dBc is achieved.