Cobalt

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Annealing Sequence Dependence of Directly Bonded InP/Si Substrate for GaInAsP Laser Diodes on a Silicon Platform

Zhao L., Sato M., Yada R., Kuroi M., Shimomura K.

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Physica Status Solidi (A) Applications and Materials Science, 2025, цитирований: 0, doi.org, Abstract

This study investigates the effects of different annealing sequences on the hydrophilic bonding of InP/Si substrates for GaInAsP laser diodes (LDs). Several annealing profiles are explored, including a process with slow temperature ramping over a specific range to minimize void formation, and compared to the traditional 8‐hour annealing process, which uses a constant annealing rate. The slow ramping approach within a targeted temperature range is found to be more effective in reducing void formation and improving bonding quality. GaInAsP lasers grown on substrates annealed using this method demonstrate improved performance, showing the potential for optimized annealing processes to enhance the quality and efficiency of bonded LDs.

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n‐type AlN/AlGaN Superlattice Cladding Layer for Ultraviolet Laser Diodes

Ebata K., Tateno K., Hirama K., Kumakura K., Taniyasu Y.

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Physica Status Solidi (A) Applications and Materials Science, 2025, цитирований: 0, doi.org, Abstract

An AlGaN laser diode (LD) on AlN substrate using an n‐type AlN/Al0.63Ga0.37N superlattice (SL) cladding layer is compared to that using a conventional n‐type Al0.7Ga0.3N alloy. An n‐type AlN/Al0.63Ga0.37N SL cladding layer with a thickness of more than 1 μm can be pseudomorphically grown on the AlN substrate, while the Al0.7Ga0.3N alloy cladding layer should be grown to a thickness of less than around 350 nm to prevent lattice relaxation. The series resistances of the LD structures are estimated to be 18 Ω for the AlN/Al0.63Ga0.37N SLs (1.5 μm) and 38 Ω for the Al0.7Ga0.3N alloy (350 nm). Because the SLs allow to pseudomorphically grow a thicker n‐type cladding layer, they are effective for reducing the lateral resistance of n‐type cladding layers and thereby the series resistance of the LD. In the electroluminescence measurement of the LD structure with SLs, the integrated emission intensity superlinearly increases and a sharp peak appears at 289.1 nm at high current injections above around 11 kA cm−2, indicating the emergence of stimulated emission. The LD structure with the SL cladding layer exhibits lower series resistance, leading to lower current density for stimulated emission than that with the alloy cladding layer.

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Sputter Epitaxy of Transition Metal Nitrides: Advances in Superconductors, Semiconductors, and Ferroelectrics

Kobayashi A., Maeda T., Akiyama T., Kawamura T., Honda Y.

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Physica Status Solidi (A) Applications and Materials Science, 2025, цитирований: 0, Обзор, doi.org, Abstract

In this review, the epitaxial growth of transition metal nitrides (TMNs) is explored, focusing on sputter epitaxy as a versatile method for developing advanced materials such as NbN superconductors and ScAlN ferroelectrics. In the recent studies, it is shown that, unlike conventional growth techniques, sputter epitaxy enables the deposition of high‐melting‐point transition metals, offering advantages for growing thin films with unique properties. In this review, recent progress in integrating TMNs with nitride semiconductors to fabricate hybrid devices that exhibit both superconducting and ferroelectric characteristics is addressed. These developments underscore the potential of sputter epitaxy as a foundational tool for advancing the next generation of electronic and quantum devices.

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Photonic Microsensor Based on a ZnO Nanowire Grown by Mist Chemical Vapor Deposition

Kouno T., Sakai M.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

A photonic microsensor is demonstrated using a ZnO nanowire grown by mist chemical vapor deposition, which is a low‐cost, low‐environmental‐impact crystal growth technique. The length and diameter of the evaluated ZnO nanowire are 13.5 μm and 600–750 nm, respectively. Under optically pumped conditions, the ZnO nanowire exhibits lasing action owing to its optical microcavity. To evaluate the sensing operation, the shift in the lasing peaks with and without a NaCl microparticle attached to the side of the ZnO nanowire is focused on. In addition, the resonant system and sensing performance of the ZnO nanowire based on the results and numerical simulations are discussed.

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Impacts of O2/(O2+Ar) Flow Ratio on the Properties of Li‐Doped NiO Thin Films Fabricated by Pressure‐Gradient Radiofrequency Magnetron Sputtering

Abe Y., Nishimura T., Yamada A.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

Herein, Li‐doped NiO thin films are deposited on glass substrates using pressure‐gradient radiofrequency magnetron sputtering, with Ar and O2 as sputtering gases. Following film fabrication, their crystal structures, optical features, and electrical properties are investigated as functions of O2 flow rate to the total flow rate (O2/(O2 + Ar)) of 10 sccm. The deposited films are also annealed at 600 °C for 1 h in an oxygen atmosphere. Notably, the resistivity of the as‐deposited films decreases significantly by three orders of magnitude from 106 to 0.0232 Ω cm when the sputtering gas is changed from pure Ar to pure O2. However, the transmittance decreases with increasing oxygen flow rate. Investigations on the temperature dependence of conductivity reveal hole conduction in the range of ≈320–420 K owing to small polaron hopping.

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Decreasing Carrier Mobility under Concentrated Illumination and Its Effect on the Series Resistance and Conversion Efficiency of Silicon Concentrator Solar Cells

Harada T., Yamashita K., Ikari T., Fukuyama A.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 1, doi.org, Abstract

The carrier mobility of solar cell materials is a critical physical parameter that determines the series resistance. Furthermore, series resistance is an essential factor affecting the conversion efficiency of concentrator solar cells under high sunlight illumination. However, there has been slight discussion regarding the relationship between these factors. In the previous study, it was reported that concentrated illumination decreased carrier mobility; however, the scattering mechanism has not yet been clarified. Moreover, carrier–carrier scattering was discussed; however, it did not cause a mobility reduction. Thus effective mass changes are discussed as a possible cause of the decrease in carrier mobility under concentrated illumination. The cause of the decrease in mobility under concentrated sunlight illumination cannot be fully elucidated; however, it is a change in lattice scattering. Furthermore, the effect of the decrease in mobility due to concentrated illumination on the series resistance and conversion efficiency of Si solar cells using numerical calculations is clarified. The increase in the series resistance caused by the mobility reduction is ≈10% under 30 suns.

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Nitride Semiconductors

Fujioka H., Miyake H., Hirayama H., Yamada Y., Funato M., Katayama R., Kojima K., Ichikawa S., Murotani H., Uemukai M.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org

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Lasing Characteristics of GaInAsP Laser Diodes on Directly Bonded InP/Si Substrates with a Gas out Channel

Zhao L., Periyanayagam G.K., Yada R., Zhang J., Kuroi M., Shimomura K.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 1, doi.org, Abstract

In this study, the lasing characteristics of GaInAsP laser diodes (LDs) grown on directly bonded InP/Si substrates with a gas out channel (GOC) structure are investigated. GOC InP/Si substrates are fabricated using hydrophilic direct bonding and metal–organic vapor phase epitaxy growth methods and subsequently their surface conditions, bonding strength, and lasing performance are examined. Herein, it is observed that the introduction of a GOC substantially reduces void formation and improves the threshold current density of the LDs. In the results, it is demonstrated that the performance of the GOC InP/Si substrates is comparable to that of InP substrates, highlighting their potential for use in high‐performance optical devices.

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Real‐Time Nuclear Magnetic Resonance Detection Using Maximum Likelihood Estimation with Single‐Shallow‐Nitrogen‐Vacancy Centers in Quantum Heterodyne Measurements

Chanuntranont A., Saito D., Otani K., Ota T., Ueda Y., Tsugawa M., Usui S., Miyake Y., Teraji T., Onoda S., Shinada T., Kawarada H., Tanii T.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 1, doi.org, Abstract

Single‐nitrogen‐vacancy (NV) centers in diamond are highly promising quantum nuclear magnetic resonance (NMR) sensors. However, their exposure to many sources of noise, such as surface impurities, shot noise from avalanche photodiode overlaps, and spin‐state projection errors inherent in quantum systems, limits their usefulness. Often, long measurement durations are required to accumulate sufficient data for NMR signal detection via fast Fourier transform spectrometry. For practical reasons, methods to shorten the necessary accumulation time for NMR signal detection are greatly desired. In this article, an on‐line formulation of maximum likelihood estimation (MLE) signal processing for quantum heterodyne NMR measurements is presented as a step toward this goal. This MLE method reduces the required data accumulation time by orders of magnitude and provides good estimates of target frequency locales in real time. These results are significant to practitioners of NMR detection with single‐NV centers in diamond who require a quick litmus test for potential signals when probing a wide area.

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Device Simulation of CsPbBr3 Solar Cells for High‐Efficiency Blue Light Photovoltaic Power Converters

Tan Y., Miyajima S.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

The performance of CsPbBr3 solar cells is investigated using device simulation to clarify the criteria for obtaining high‐efficiency blue light photovoltaic power converters. The results show that the conduction band offset between the electron transport layer (ETL) and CsPbBr3 layer significantly impacts conversion efficiency. The best device performance is obtained when the conduction band of the ETL is 0.4 eV higher than that of the CsPbBr3 layer. Simulations also revealed that gallium nitride is preferred to conventional titanium oxide (TiO2) as the ETL material. The analysis indicates that the carrier diffusion length of the CsPbBr3 layer significantly affects the short‐circuit current density and fill factor of devices and that a carrier diffusion length of at least 0.5 μm is required to realize high‐efficiency devices. The use of a transparent conductive oxide layer with a work function smaller than 4.0 eV or the insertion of a buffer layer with electron affinity less than 4.1 eV can effectively improve the open‐circuit voltage of devices.

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Photo‐ and Radioluminescence Properties of (Gd3+/Ce3+) Coupled Ions Activated Sodium‐Aluminum‐Oxyfluoride‐Phosphate Glasses for X‐ray Detecting Material

Meejitpaisan P., Doddoji R., Jarucha N., Sarumaha C., Kantuptim P., Yanagida T., Kaewkhao J.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

Oxyfluoride‐based sodium‐aluminum‐phosphate glasses with a fixed 7 mol% content of Gd2O3 and various amounts of CeF3 were fabricated by the melt quenching process. The fabricated glasses (NAPGCe) were studied by physical, optical, scintillation, and light yield properties. In NAPGCe glasses, intense emission peaks were observed at 312 nm (6P7/2 → 8S7/2) for Gd3+ and 336 nm (5d → 4f) for Ce3+ ions in both photoluminescence (275 and 294 nm) and radioluminescence (X‐ray) spectra. Upon excitation with 275 nm ultraviolet radiation, a decrease in Gd3+ emission and an increase in Ce3+ emission intensity lead to efficient energy transfer (ET) from Gd3+ to Ce3+ ion in NAPGCe glasses. The bi‐exponential function was applied to fit the non‐exponential decay curves of NAPGCe glasses and then calculated their lifetimes in the order of fast (18.25–16.94 ns) and slow (72.99–67.74 ns) decay times. An overall integrated scintillation efficiency of about 67% was estimated for NAPGCe0.10 glass compared to bismuth germanate oxide (BGO:Bi4Ge3O12) crystal. Under 241Am α‐ray (5.5 MeV) source, the light yield of the NAPGCe1.00 glass was obtained by comparing it with a commercial Li‐glass scintillator (GS20), and it was found to be 26 photons MeV−1.

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Annealing Time Dependence on Creation of SiV, GeV, and SnV in Diamond by Atmospheric Annealing at 1800 °C

Baba T., Iizawa M., Takenaka K., Kimura K., Kawasaki A., Taniguchi T., Miyakawa M., Okazaki H., Hanaizumi O., Onoda S.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

The creation of SiV−, GeV−, and SnV− are presented by the atmospheric annealing in the argon flow. Compared to high‐pressure annealing, in which gas cannot flow, atmospheric annealing with an inert gas flow not only causes less degradation of the sample surface but also has the advantage of reducing equipment cost and preparation time. Excessive annealing time has been shown to reduce the amount of centers created. The optimal annealing time that maximizes formations depends on the type of diamond sample and the implanted ions. Furthermore, inspired by the split‐vacancy structure of the group IV–V centers, atmospheric pre‐annealing at 600 °C to increase the amount of di‐vacancy is demonstrated, followed by annealing at 1800 °C for 1 min. A shorter duration of high‐temperature annealing is expected to qualitatively reduce stress and deterioration of the crystallinity of the diamond sample.

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Enhanced Photocatalytic Activity of Anatase/Rutile‐Mixed Phase Titanium Dioxide Nanoparticles Annealed with Polyethylene Glycol at Low Temperatures in Aluminum Foil‐Covered Combustion Boats

Kawakami R., Matsumoto T., Yanagiya S., Shirai A., Nakano Y., Niibe M.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 1, doi.org, Abstract

A facile carbon‐doping process is proposed to enhance the photocatalytic activity of anatase/rutile‐mixed phase TiO2 nanoparticles using polyethylene glycol (PEG). The TiO2‐PEG composite is loaded into a boat and covered tightly with Al foil to increase the pressure inside that boat during annealing. The boat is annealed for 1 h at different temperatures and PEG ratios. The annealing with 30% PEG at 300 °C enhances the decomposition of organic pollutants and bacterial inactivation under 405 nm light compared to the annealing without Al films. This annealing causes 2.5–3% carbon doping, introduces more oxygen vacancies, and converts PEG into organic compounds rich in CC bond components. These modifications of TiO2 can be attributed to carbon‐centered radicals produced from PEG during annealing. The modifications change the band structure to enhance the photogenerated carrier concentration responsible for the photocatalytic activity. The carbon doping narrows the anatase and rutile bandgaps, allowing the anatase phase to absorb 405 nm light. The introduced oxygen vacancies increase the electron‐trapping sites and raise the adsorbed oxygen groups enhancing the upward band bending and the depletion layer depth at the surface. The PEG‐converted compounds can transfer photogenerated electrons within the compounds to the TiO2 conduction band.

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Elimination of V‐Shaped Pits in Thick InGaN Layers via Ammonia‐Assisted Face‐to‐Face Annealing

Nakata A., Sasaki A., Kurai S., Okada N., Yamada Y.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

InGaN, a group‐III nitride semiconductor, is expected to be widely used in the field of optoelectronics, owing to its excellent physical properties. However, InGaN has various limitations. This study reports face‐to‐face annealing (FFA) using vapor‐phase and in‐plane mass transport to improve the surface flatness of an InGaN template. InGaN layers are grown on a GaN template that is grown on a c‐plane sapphire substrate using metal–organic vapor‐phase epitaxy. NH3‐assisted FFA is performed at 1050 °C for 20 min, causing V‐pits to vanish from the InGaN template despite their initial density of 3.3 × 108 cm−2. The surface condition of the lower InGaN layer is worse than that of the upper InGaN layer due to the FFA‐induced upward mass transport from the lower layer, thereby eliminating the V‐pits. Compositional analysis of the upper layer through Auger electron spectroscopy and energy‐dispersive X‐ray spectroscopy reveals In peaks despite high‐temperature annealing, thus confirming the presence of InGaN. The results of this study offer possibilities for future InGaN crystal growth and InGaN‐based device fabrication.

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A Model of Wafer Warpage for Trench Field‐Plate Power MOSFETs

Kato H., Cai B., Yuan J., Miyamura Y., Nishizawa S., Saito W.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

A new wafer warpage model is proposed for the full process design of trench field‐plate (FP) power metal‐oxide‐semiconductor fileld‐effect transitors (MOSFETs) using large‐sized wafer. Trench FP power MOSFETs feature a deep trench and thick oxide at the wafer surface. Wafer warpage occurs due to the stress imbalance between the front and back sides of the wafer. This warpage leads to significant problems with transport errors in manufacturing equipment. This issue is expected to become even more crucial as lateral pitch narrowing is employed to reduce on‐resistance. In this study, two methods are compared to estimate the warpage of a 200 mm diameter Si‐wafer after trench etching and oxidation process. The mechanical stress generated by the oxidation process in several cell units is calculated using a 3D simulation. In the first approach, wafer warpage is converted from the displacement of the cell units. In the second approach, wafer warpage is estimated based on the surface film stress, which is calculated in the 3D simulation. The second approach shows good agreement with experimental results and is applicable to the 300 mm diameter Si process. This method yields more accurate measurements than the method using displacement.

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Microwave Power Performance of AlGaN/GaN High‐Electron‐Mobility Transistor on Semi‐Insulating Mn‐Doped GaN Substrate

Sugino T., Osaki K., Nonaka K., Sugiyama T., Kuraoka Y., Wakejima A.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

Herein, a DC and microwave performance of 2 μm gate length AlGaN/GaN high‐electron‐mobility transistor (HEMTs) on a Mn‐doped GaN substrate is demonstrated. The maximum drain current is 670 mA with a threshold voltage of 2.5 V and with good pinch‐off characteristics. The breakdown voltage of the HEMT is ≈80 V. The HEMT shows Δ8% current collapse while referenced HEMT on a SiC substrates which is fabricated simultaneously shows large Δ30% current collapse. When the HEMT with a gate width of 100 μm is tuned for the maximum output power at 2.4 GHz with a drain voltage of 30 V, it delivers 500 mW (5 W mm−1) with the maximum drain efficiency of 54%. These output performances are in good agreement with ideal class‐A operation performance. Therefore, it is concluded that the HEMT on Mn‐doped GaN substrates is promising for future microwave and millimeter‐wave high‐power transistors.

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Influence of Aluminum Pillar Nanostructures on Thin‐Film Organic Solar Cells

Phengdaam A., Sitpathom N., Hong M., Shinbo K., Kato K., Baba A.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

This study explores the application of pillar nanostructures in organic solar cells (OSCs). The aluminum pillar nanostructures (AlPNSs) are fabricated on an active layer surface comprising of a blend poly(3‐hexylthiophene‐2,5‐diyl) and [6,6]‐phenyl C61 butyric acid methyl ester using nanoimprinting. Aluminum back electrodes are formed, resulting in AlPNSs with an imprinted pattern height of 60 ± 6 nm and a pitch of 212 ± 49 nm. Atomic force microscope images and current density versus voltage curves are obtained for the fabricated devices, both with and without AlPNSs. The results indicate a solar cell efficiency increase of 15.16% in the AlPNS OSCs compared to the reference cells. To investigate the role of AlPNSs in the enhancement, impedance spectroscopy, incident photon‐to‐current efficiency, UV–Vis reflection spectroscopy, and finite‐difference time‐domain simulations are performed for the both devices. The results demonstrate that the combination of propagating surface plasmon resonance and light‐trapping properties due to AlPNSs significantly enhances the overall optical performance. This research provides new insights into the potential of imprinted nanostructures for enhancing OSC performance, including their plasmonic and optical characteristics.

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Spatial and Size Distributions of Ti(C5H7O2)2[(CH3)2CHO]2 Mist Particles in a Tubular Furnace for Conformal and Uniform Deposition of Amorphous TiO2 Thin Films

Kuddus A., Sato T., Yokoyama K., Shirai H.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

The spatial and size distributions of titanium diisopropoxide bisacetylacetonate [(C5H7O2)2[(CH3)2CHO]2, also known as Ti(acac)2(OiPr)2] mist, diluted in CH3OH, are investigated in a tubular furnace using atmospheric‐pressure mist chemical vapor deposition (mist CVD). The focus is on the deposition of amorphous (a)‐TiO2 films with tubular furnace temperature and mesh bias as variables. When the furnace temperature reaches 350 °C, the number density of mist particles increases without significant changes in their size distribution, leading to a higher film deposition rate. Further, the deposition rate and average size of the mist particles with lower adhesion coefficient decrease with increasing spatial distance from the furnace inlet. Furthermore, applying a mesh bias results in an increase in the maximum number density of mist particles with a narrower size distribution; however, the overall film deposition rate decreases. These variations are attributed to the chemical reactivity of the mist precursors produced by pyrolysis and mesh bias. The fine mist precursors, which are strongly charged, coordinate with CH3OH and CHO groups through solvation, enhancing their chemical stability and lifetime. This process yields a dense and rigid a‐TiO2 network, improving the junction properties at the a‐TiO2/c‐Si interface.

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Design of Horizontally Stacked AlN and Dielectric Cores Transverse Quasi‐Phase‐Matched Channel Waveguide for Squeezed Light Generation

Honda H., Noro R., Uemukai M., Tanikawa T., Katayama R.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

AlN is a promising candidate for photonic integrated circuits. In this study, horizontally stacked transverse quasi‐phase‐matched (QPM) waveguides with an AlN center core and Si3N4, Ta2O5, and TiO2 side cores were designed to generate squeezed light at 920 nm. The squeezing level was calculated by considering the propagation loss at the wavelengths of the squeezed light and pump light. Using TiO2 for the side cores enhanced the electric field amplitude of the pump light in the AlN center core, and a high nonlinear coupling coefficient was obtained. Owing to the small propagation loss of the AlN waveguide on sapphire and high nonlinear coupling coefficient of the transverse QPM with TiO2 side cores, a squeezing level of over 8.1 dB was expected with a 1 cm long waveguide and pump power of 70 mW.

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Concentrations Influence of Complexing Agents on the Physicochemical Properties of Chemical Bath Deposited n‐Type FeSxOy for Homostructure Solar Cell

Ariff A.A., Supee A., Ichimura M., Mohd Yusop M.Z., Abdul Jalil A.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

A chemical bath deposition (CBD) is applied to deposit n‐type iron sulfide (FeSxOy) film on fluorine (F)‐doped tin oxide (SnO2)–FTO substrate. The duration, temperature, and magnetic stirrer's speed in CBD are 3 h, 75 °C, and 100 revolutions per minute. The influence of complexing agents’ concentration (≤200 mm)–acid (tartaric and lactic) on the physicochemical properties of film is studied. All films are n‐type semiconductors with large bandgap (2.95–3.58 eV) and contain high oxygen (≈56–83%). Scanning electron microscopy image shows the 50 mm tartaric acid film has a uniform and denser surface morphology. FeSxOy film with tartaric acid has lesser goethite and hematite peaks in X‐ray diffraction than lactic acid. The FeSxOy film with 100 mm lactic acid exhibits a slightly higher transmittance at ≈350–450 nm. The FeSxOy homostructure reveals average open‐circuit voltage (Voc) = 0.45 V, short‐circuit current (Jsc) = 0.0003 mA cm−2, fill factor =38%, and efficiency (η) = 0.57%.

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Cover Picture

Khan M.A., Yamada Y., Hirayama H.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org

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Current Saturation Behavior in GaN Polarization Superjunction Hybrid Diode

Du Y., Sankara Narayanan E.M., Kawai H., Yagi S., Narui H.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

This is the first report on the current saturation behavior observed in the forward characteristics of polarization superjunction (PSJ)‐based hybrid PiN‐Schottky GaN power diodes fabricated on Sapphire. In the current saturation region, most of the applied anode voltage is dropped across the regions immediately adjacent to the edge of the doped P‐GaN region closest to the cathode. This significant potential drop occurs within a short distance, resulting in a high electric field and depletion of electrons, causing the current saturation behavior via velocity saturation in these PSJ hybrid diodes.

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Light B Doping by Ion Implantation into High‐Purity Heteroepitaxial Diamond

Seki Y., Yoshihara M., Kim S., Koyama K., Hoshino Y.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

The low‐concentration boron doping is performed from 1016 to 1018 cm−3 by ion implantation into heteroepitaxially synthesized large‐area diamond and electrical properties are investigated. Photoluminescence analysis is first carried out to clarify the optical properties of the heteroepitaxial diamond substrate. As a result, defect complexes of nitrogen‐vacancy and silicon‐vacancy are hardly detected in this substrate, suggesting that optically high‐purity diamond can be accomplished by heteroepitaxial growth. Then, the electrical properties of resistivity, mobility, carrier concentration, and conductive type by Hall effect measurements are investigated. For the samples with doping concentrations higher than 1016 cm−3, the electrical activation of implanted B acting as acceptors is confirmed. The compensation ratio for the sample with 3.5 × 1017 cm−3 concentration reaches 76%, indicating the presence of compensating donor‐like centers. With increasing the doping concentration to 3.5 × 1018 cm−3, the compensation ratio is significantly reduced to 35%. The observed mobility of the higher doped sample takes almost the ideal value observed for the sample doped by chemical vapor deposition process. It is suggested that the heteroepitaxial synthesis of large‐area and high‐purity substrates should contribute to the further development of the application to electronic, optical, and sensing devices in the future.

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Hybridly Packaged White Light Emitting Diode Composed of Fluorescent SiC and Nitride‐Based Near‐Ultraviolet Light Emitting Diode

Mizuno T., Akiyoshi S., Iwaya M., Takeuchi T., Kamiyama S., Ou Y., Ou H.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

A combination of fluorescent SiC (f‐SiC) and porous f‐SiC is a promising phosphor material for pure white light emission. Herein, the anodic oxidation condition is optimized to produce porous f‐SiC. Furthermore, a hybridly packaged white light emitting diode (LED) package composed of f‐SiC/porous f‐SiC stacks with a nitride‐based NUV‐LED as an excitation source is fabricated. A distinct pure white light emission and the peak luminous efficacy of 11.6 lm W−1 at a forward current of 10 mA in the NUV‐LED are observed. At the peak luminous efficacy, the estimated internal quantum efficiency of the f‐SiC/porous f‐SiC stacks is ≈80% as the package involved several types of optical and energy losses.

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GaInN‐Based Blue LED with a PEDOT/PSS Hole Transport Layer

Kato Y., Iwaya M., Takeuchi T., Kamiyama S.

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Physica Status Solidi (A) Applications and Materials Science, 2024, цитирований: 0, doi.org, Abstract

In this study, a nitride‐based blue PEDOT‐LED is fabricated and a preliminary assessment of the device characteristics is done. To prevent detaching of the PEDOT/PSS layer from the LED substrate when immersing in water or developing solution, Ag was deposited on top of the PEDOT/PSS layer. Additionally, exfoliation is suppressed by reducing the developing time and protecting the wafer edge with a photoresist. Different etching methods for Ag and PEDOT/PSS are investigated. The Ar ion‐beam etching resulted in uniform and flat‐etched surfaces. Regarding the performance of the PEDOT‐LEDs, a high Mg‐doping concentration of 1.0 × 1020 cm−2 leads to a relatively low threshold current voltage in the V–I characteristics. However, for the PEDOT‐LED with p‐Al0.25Ga0.75 N EBL, a steep light output saturation is observed at high current density when analyzing the L–I characteristics.