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This study aimed to assess the association between physical frailty and clinical outcomes among older patients hospitalized for pneumonia.This study examined 852 consecutive patients hospitalized for pneumonia between October 2018 and September 2020. Patients who were65 years old, scheduled for admission, did not receive inpatient rehabilitation, or died during admission were excluded. A short physical performance battery (SPPB) test was performed by physical therapists upon discharge. The primary outcome measure was a composite endpoint of readmission or mortality due to any cause within 6 months of discharge.In total, 521 patients (median age, 80 years; interquartile range, 74-86 years) were included in the analyses, and were divided into the following two groups: robust group with SPPB scores9 (n = 150), and physical frailty group with SPPB scores ≤9 (n = 371). Of these, 346 (66.4%) patients were men; and the median SPPB score was 6 (interquartile range, 1-10). During the median follow-up period of 53 days (interquartile range, 4-180 days), 92 (17.6%) patients were readmitted and 25 (4.8%) patients died. Patients with physical frailty were at an increased risk for the primary endpoint (hazard ratio, 2.21; 95% confidence interval, 1.44-3.41; P 0.001); the risk remained significant after adjusting for multiple variables (adjusted hazard ratio, 1.70; 95% confidence interval, 1.05-2.74; P = 0.028).Among older patients with pneumonia, physical frailty status at discharge was an independent risk factor for readmission and mortality within 6 months after initial discharge. Geriatr Gerontol Int 2021; 21: 926-931.

The bending of slide‐ring materials (SRMs), polymer materials having ring‐shaped cross‐linking points providing deterioration tolerance and low hysteresis, is described. An SRM sheet exhibits a voltage‐controllable, extremely large, fast, and bidirectional bending deformation with shape memory functionality. A 50‐μm‐thick SRM sheet actuator exhibits an electrostatic actuation in two opposite directions and bending angle larger than 180° achieved within 0.4 s due to its shape memory effect. The memory effect remains for more than 250 min. As a potential application utilizing the bending of the SRM, a soft gripper is fabricated, which handles two objects placed opposite each other. This functionality is rarely achieved by a soft gripper composed of a single active material, which shows the characteristics of the SRM promising for the development of soft matter systems with novel functionalities and high performances.

This paper reports the post-growth annealing effects of low-temperature grown Mg-doped InGaN. By using MOVPE, 1 μm-thick Mg-doped InxGa1–xN (x ~ 0.36) films are grown at 570 °C. In order to activate the Mg acceptors, grown samples are treated by the conventional furnace annealing (FA) or the rapid thermal annealing (RTA). In the case of the FA at 650 °C for 20 min, the InGaN film is phase-separated. On the other hand, the RTA at a temperature higher than 700 °C enables us to get p-type samples. By using the RTA at 850 for 20 s, p-type samples with a hole concentration 1018–1019 cm−3 are successfully obtained without phase separation.

Group-III nitride on Si tandem solar cell structures, which are free from materials with high impacts on the environment such as group-III arsenides or phosphides, were successfully fabricated using the surfaceactivated bonding of nitride-based sub cells, which had been grown on (0001) GaN substrates, and (111) Si-based sub cells. The backsides of the GaN substrates had been polished and their averaged roughness was smaller than 1 nm prior to bonding. The open-circuit voltage (VOC) of the tandem cells was almost equal to the sum of VOC of the respective sub cells, while the conversion efficiency was limited by the properties of the nitride-based top cells. Nitride-on-(100) Si tandem cells were also fabricated and the enhancement in VOC was observed. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Studies of ambient-pressure and high-pressure behavior of photoluminescence (PL) for series of InxAl1-xN layers are presented. The measured evolution of PL energy (E-PL) with x is characterized by a clear decrease of E-PL and exhibits a strong bowing. This dependence corresponds to the predictions of ab initio calculations of the band-gap energy changes E-G with x. However, values of E-PL are clearly lower than E-G, for 0

This paper reports the application of InGaN films to a polymer electrolyte cells (PEFC) stainless steel (SS) separator for the first time. Using MOCVD, InGaN films with In content of 0-1 are grown at 600 °C on sapphire and stainless steel substrates. Sputtered TiN is used as a buffer for the InGaN growth on stainless steel. For InGaN on sapphire substrates, electrical resistivity and dissolution rate in a H2SO4 solution at 60 °C are measured, and films with In content in the range 0.2-0.5 are found to have both high electric conductivity and high corrosion resistance. The anti-corrosive properties of In0.3Ga0.7N/TiN/SS structures are also confirmed by the inductively coupled plasma spectrometry (ICP) chemical analysis of the H2SO4 solution in which the In0.3Ga0.7N/TiN/SS samples are dipped for 100 h. The levels of both Ga and In atoms are under the detection limits. The I-V characteristics of a single cell using an In0.3Ga0.7N/TiN/SS separator is measured in comparison with those using bare stainless steel or carbon separators. The performance of the cell with the In0.3Ga0.7N/TiN/SS separator is much superior to that with a bare stainless steel. Compared with the cell using the carbon separator, the cell using the In0.3Ga0.7N/TiN/SS separator has a little larger ohmic loss (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports on a theoretical analysis of DC and RF performances of a novel In0.1Ga0.9N/InN HEMT. A very high cut-off frequency and attractive DC characteristics have been predicted. A simple analytical model is used to explain the DC characteristics. The cut-off frequency which has been found more than 0.6 THz for a gate length of 0.1 µm is explained with low-field mobility. The maximum drain current and transconductance have been found around 1000 mA/mm and 625 mS/mm, respectively. Similar analysis have been performed for the conventional AlGaN/GaN HEMT and compared with the proposed InGaN/InN HEMT. The predicted results are found to be in good agreement with previously published results. The calculated results show that InN-based HEMT has very high cut-off frequency and transconductance when compared with the conventional GaN-based HEMT for the same gate length. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Quantum confinement effect on 2DEG density and distribution on the dependence of an interfacial layer has been investigated in InGaN/InN HEMT using self-consistent solution of one dimensional Schrodinger-Poisson equation. It is shown that the addition of an i-InGaN interfacial layer leads to an increase in 2DEG density. The role of quantum confinement effect in the 2DEG distribution with an inserted i-InGaN interfacial layer is revealed. In the classical model, the insertion of an interfacial layer has a negligible effect on 2DEG distribution. While taking the quantum effect along with polarization effect into account, it is observed that i-InGaN interfacial layer has substantial influence on the 2DEG distribution in InGaN/InN HEMT; with electron spillover into the barrier is sharply reduced. The maximum 2DEG density after insertion of an i-InGaN interfacial layer has been found to be 1 × 1014 cm-2 which is higher than the conventional GaN-based HEMT (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The aim of this study was to evaluate the effects of implemented control measures to reduce illness induced by Vibrio parahaemolyticus (V. parahaemolyticus) in horse mackerel (Trachurus japonicus), seafood that is commonly consumed raw in Japan. On the basis of currently available experimental and survey data, we constructed a quantitative risk model of V. parahaemolyticus in horse mackerel from harvest to consumption. In particular, the following factors were evaluated: bacterial growth at all stages, effects of washing the fish body and storage water, and bacterial transfer from the fish surface, gills, and intestine to fillets during preparation. New parameters of the beta-Poisson dose-response model were determined from all human feeding trials, some of which have been used for risk assessment by the U.S. Food and Drug Administration (USFDA). The probability of illness caused by V. parahaemolyticus was estimated using both the USFDA dose-response parameters and our parameters for each selected pathway of scenario alternatives: washing whole fish at landing, storage in contaminated water, high temperature during transportation, and washing fish during preparation. The last scenario (washing fish during preparation) was the most effective for reducing the risk of illness by about a factor of 10 compared to no washing at this stage. Risk of illness increased by 50% by exposure to increased temperature during transportation, according to our assumptions of duration and temperature. The other two scenarios did not significantly affect risk. The choice of dose-response parameters was not critical for evaluation of control measures.

This paper describes the theoretical design and performance of a novel InGaN-based 1.55 μm quantum well laser. A careful analysis of the optical and modal gain, threshold behavior, optical output, and efficiency with cavity length has been carried out. The spectral range of the optical material gain is found to be narrow and modal gain varies sharply with changing the reflectivity of the partially transparent mirror. It is found that a very small voltage of 1.10 V is required to reach the threshold current. A very small threshold current of 5.1 mA is required to emit the light. The calculated values of threshold current and threshold voltage are lower than the reported values of the conventional 1.55 μm laser. An efficiency of around 59% is found for a cavity length of 300 μm keeping the reflectivity at 35% of one mirror and 100% of other. The above study indicates that the proposed InGaN-based 1.55 μm laser is very promising for the fabrication of future high performance laser (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper describes a novel AlInN/InN metal-oxide-semiconductor heterojunction field effect transistor (MOSHFET) as a promising candidate for future high performance microwave devices. The transport properties such as channel mobility and velocity-field characteristics of the proposed AlInN/InN MOSHFET are calculated using Monte Carlo simulation. The DC and high frequency performances are assessed using an analytical model. The highest mobility is found to be 8.1×104 cm2V–1s–1 at a sheet carrier concentration of 8.79×1012cm–2. The peak drift velocity obtained for the device is 8.3×107 cm/s at the field of 66 kV/cm. The maximum cut-off frequency, transconductance and drain current have been found 160 GHz, 280 mS/mm, and 879 mA/mm, respectively, for a gate length of 0.25 μm. The calculated results are in good agreement with the published results of GaN MOSHFET (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper describes the 2DEG properties of InGaN/InN/InGaN double channel high electron mobility transistor (DHEMT). These include an in-depth theoretical investigation of 2DEG sheet carrier concentration and mobility. The 2DEG mobility is calculated using ensemble Monte Carlo taking into account all relevant scatterings. The calculated sheet carrier concentration reaches as high as 1.77×1014 cm-2 for DHEMT. While for single channel high electron mobility transistor (SHEMT) the calculated sheet carrier concentration was found to be 7.06×1013 cm-2. The maximum total 2DEG mobility is found to be around 12×104 and 8×104 cm2V-1s-1, respectively, for DHEMT and SHEMT for a sheet carrier concentration of ns = 5×1012 cm-2 at 77 K. Thus, the 2DEG sheet carrier concentration and mobility for dual channel is higher than conventional single channel HEMTs. The high values of 2DEG sheet carrier concentration and mobility strongly suggest that the InGaN/InN/InGaN based double channel HEMT is very promising for the fabrication of high performance high speed device (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the effect of step-graded interlayers on MOVPE InGaN epi-layer quality. Multilayer epitaxial structures consisting of Inx Ga1–xN layers with various compositions have been successfully grown. HRXRD measurements reveal that the insertion of step-graded interlayers significantly reduces the twist while little effects are observed on tilt. Decreasing of twist with increasing the number of interlayers is found to be remarkable up to a certain value and then maintain nearly the same even with increasing the In composition. Different types of dislocation density have also been studied using the X-ray diffraction analysis. Dislocation densities, particularly the edge dislocation density, decrease considerably with the insertion of interlayers for higher In composition. An edge dislocation of 3 × 1010 cm–2 is obtained for a smple with 0.25 In composition, that seems to come from the GaN layer beneath the step-graded interlayers (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, we review and discuss the recent advances in InN-based solar cells. Before the discussion on InN-based solar cells, two major losses in a solar cell, transparency loss and excess excitation loss, are explained and the effectiveness of a multi-junction tandem cell in reducing the both losses simultaneously is described. Then, the status and issues for multi-junction tandem solar cells using the conventional III-V materials (InGaP/InGaAs systems) are reviewed briefly in order to understand the advantages of InN-based material as a multi-junction solar cell material. It is shown that main problem in the conventional III-V multi-junction solar cell is the current mismatching between sub-cells, which reduces significantly the conversion efficiency of the tandem cells. The main advantage of InGaN and InAlN as a multi-junction solar cell is that a wanted band-gap between 0.7 and 2.5 eV is realized by changing only their composition. This means that current matching between sub-cells will be easily achieved using InGaN and InAlN systems. After the status of InGaN solar cell research is summarized, the results on the MOVPE growth of InGaN with an In content up to 0.4, Mg doping using Cp2Mg, and the formation of an n+-p homo-junction are described. The insertion of step-graded InxGa1-xN interlayer between the GaN and InGaN epilayer is also shown to be effective to improve the epilayer quality. The study on InAlN solar cell is on the stage of the growth of In-rich InAlN. Single-crystalline InAlN films with an Al content from 0 (Eg = 0.7 eV) to 0.43 (2 eV) have been successfully grown by employing atmospheric-pressure MOVPE. The study on Mg-doping for InAlN will be the next step. Finally, we will summarize and discuss the challenges in InGaN and InAlN solar cells. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the atmospheric-pressure MOVPE growth of In-rich InAlN. All InAlN films prepared here (Al content:0∼ 0.43) do not show phase separation. The incorporation of Al in InAlN is decreased with increasing growth temperature. A decrease in Al content is also observed for films grown at a position farther from the up-stream end of the susceptor. The marked decrease in the Al content along the gas flow direction seems to be caused by the shortage of TMA supply at the downstream by the parasitic reaction of TMA. A single-crystalline InAlN film with an Al content of 0-0.43 is successfully grown by adjusting growth temperature and TMA/(TMI+TMA) molar ratio. FWHM of X-ray rocking curve for InAlN is increased with increasing Al content. The carrier concentrations in InAlN films are comparable to that in InN (1-5 × 1019 cm–3). All the single-crystalline InAlN films with an Al content of 0-0.3 show a photoluminescence at room temperature. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Improvements in the success of cancer treatments have resulted in increased awareness of the long-term effects of treatment, of which gonadal failure is the most significant. Thus, preservation of fertility potential has become a major goal and could be realized by preventing ovarian toxicity or by cryopreservation of reproductive cells/tissues. This review aimed to critically discuss the current protocols for the management of chemotherapy-inducced/radiotherapy-induced premature ovarian failure (POF). A medical approach using the gonadotropin-releasing hormone analog (GnRHa) may act to protect the gonads during radiation and/or chemotherapy by preferentially steering cells into cell cycle arrest with a decline in responsibility to the chemotherapeutic agents. Ovarian protection by GnRHa cotreatment against chemotherapy can enable the preservation of future fertility in survivors and prevent the bone demineralization and osteoporosis associated with hypestrogenism and POF. In vitro fertilization of retrieved oocytes could enable embryo freezing in some patients. Embryo cryopreservation is considered standard practice and widely available, but may seldom be used because of a lack of a male partner, the need to postpone cancer therapy for a few weeks and the possibility that an estrogen rise may be undesirable in sensitive cancer patients. Improvement in oocyte cryopreservation may offer additional possibilities; the prolonged culture of primordial and primary follicles in vitro is still unfeasible. Currently, the cryopreservation of ovarian cortex, which hosts thousands of immature follicles, is an investigational method, but has the advantage of requiring neither a sperm donor nor ovarian stimulation. Fertility preservation is often possible in women undergoing cancer treatment. To preserve the full range of options, fertility preservation procedures should be considered as early as possible during therapy planning.

The Mg doping for MOVPE InN has been studied using biscyclopentadienyllmagnesium CP2Mg as a Mg source. The InN samples grown near the upstream end of the 18 cm long susceptor have very small grain size and contain a high level of C and H contamination. The XPS analysis of the deposits obtained by the supply of CP2Mg together with NH3 reveals that new Mg compounds are formed near the upstream end of the susceptor. The new compounds are adducts of CP2Mg and NH3, because they can not be formed when only CP2Mg is supplied. The adduct formation seems to be a cause for the very small grain size and the high levels of C and H contamination. The adduct formation is suppressed at positions with a distance more than 9 cm from the upstream end. This means that designs of reactor and susceptor are very important for successful Mg doping of InN with CP2Mg. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the crystallographic degradation of MOVPE InN during the growth. Using FWHMs of X-ray rocking curve, tilt ((0002)) and twist ((10-10)) angle distributions are evaluated and effects of the major growth parameters, such as growth temperature, growth time and with/without GaN buffer in the degradation, are revealed. With increasing either thickness of grown InN or growth temperature up to 600 °C, the tilt angle distribution is markedly increased, indicating the crystallographic degradation of grown films. The use of a GaN buffer reduces such degradation. Since the twist angle distribution is scarcely changed by such growth parameters, the destruction of InN crystals during growth and annealing is concluded to be anisotropic. The trends of the crystallographic degradation revealed here are in good agreement with those for the electrical and optical degradation previously reported. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An experimental study has been made on the correlation between the fabrication conditions for 3c-SiC/Si (111) template and electrical and crystallographic properties of InN films grown on the templates. The template has been prepared by C+-ion implantation into Si (111). Although the 3c-SiC layers show a large (170 arcmin) FWHM of XRC (111) diffraction, InN films with a considerably small (about 50 arcmin) FWHMs for (0002) and (10-10) diffraction are grown on the layers. A lower implantation dose brings a smaller XRC FWHMs for 3c-SiC. The post implantation annealing is found to be effective to improve the quality of the 3c-SiC layer and, therefore, to improve the quality of InN films. Hall mobility in InN is found to be markedly increased by decreasing FWHM of InN (0002) diffraction. The best data of carrier concentration and Hall mobility are 6.2×1018 cm–3 and 630 cm2/Vs, respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have investigated quantitatively on the origins of residual electrons in InN layers to make clear some roles of oxygen incorporation for band-gap widening. It has been found out that a linear relation was observed between oxygen and residual electron concentrations for InN layers grown by RF-MOMBE using TMIn source, although the residual electron concentration is super-linearly dependent on oxygen concentration for InN layers grown by RF-MBE using metal In source. The experimental results strongly indicate that oxygen atoms and/or nitrogen vacancies induced by oxygen incorporation are major origins of the residual carrier concentrations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Polarity control of MOVPE InN on sapphire (0001) was investigated. Two kinds of polarity InN films on sapphire substrate by MOVPE have been prepared by controlling the substrate nitridation process and/or the LT-GaN buffer annealing process. Surface of the nitrided sapphire is a crucial factor in determining the polarity of InN film. N-polarity InN film was grown on the 1000 °C-nitrided substrate without LT-GaN buffer; while In-polarity InN film was grown on the 900 °C-nitrided substrate. In the case of InN growth with a LT-GaN buffer, buffer annealing is a crucial issue in determining the polarity of InN film. N- and In-polarity InN films were obtained on the long-time-annealed buffer and the short-time-annealed buffer, respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have investigated about a control technique of oxygen contamination into the InN layers by simultaneous irradiation of Ga beam during RF-MOMBE growth using the combination of the TMIn and the RF-plasma nitrogen sources. Red shifts of the band gap energy and the improvement of the electrical properties have been achieved by the Ga beam irradiation. The suppresssion mechanism of the oxygen contamination has been discussed from the experimental results of the InN growth by the RF-MOMBE with the Ga beam irradiation. The present results strongly indicate that the simultaneous irradiation of the Ga beam would be useful to suppress the oxygen contamination into the InN layers during the growth. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the residual tensile stress in GaN grown on 3c-SiC/Si template formed by C+-ion implantation into Si(111). A GaN layer is grown using MOVPE method with the conventional two-step growth. The residual tensile stress is dependent on the fabrication conditions of the template, such as substrate temperature for implantation, acceleration voltage of C+-ions, temperature and time for the post-implantation annealing of Si wafers. It is found that the substrate temperature during implantation is a predominant factor. The residual stress in GaN layer is reduced from 1.3 to 0.45 GPa when the substrate temperature during implantation is changed from 400 to 600 oC. The stress is also decreased by increasing accelerating voltage for implantation and post-implantation annealing time. The residual tensile stress of 0.45 GPa is the lowest one ever reported for GaN on Si. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The influence of substrate polarity on the growth of InN film by MOVPE was investigated using bulk GaN as a substrate. Single-crystalline In- and N-polarity InN films were obtained on Ga- and N-polarity GaN substrate, respectively. Significant difference of the morphologies between the In- and N-polarity InN films was found. For the In-polarity InN film, the morphology was similar to that grown on sapphire substrate. The film surface was consisted of grains with small facets. In contrast, for the N-polarity InN film, the surface was consisted of large hexagonal shape crystal grains with flat surface. The grain size was about 2 μm in diameter on the average, and two-dimensional growth was enhanced obviously for each crystal grain. The influence of the growth temperature on the morphology, polarity, and optical property was also investigated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The deterioration of MOVPE InN during the growth and the post-growth annealing processes is investigated. Photoluminescence (PL) measurement with excitation sources with a different wavelength is mainly used to detect deterioration of InN. This is aimed to get in-depth information about the quality of InN since the penetration depth of an excitation source is different depending on its wavelength. A serious deterioration, which is the decomposition of InN, is found for InN annealed in the NH3 flow after the growth. The deterioration occurs predominantly near the substrate interface. On the contrary, the deterioration of InN during growth is scarcely observed. Since the InN films grown on sapphire have an In-polarity, the deterioration during the post-growth annealing occurs at the N-surface. Such deterioration is suppressed by the supply of TMI together with NH3 (InN growth mode). From these facts, hydrogen produced by the decomposition of NH3 seems to be responsible for the deterioration since hydrogen is consumed to form CH4 when TMI is supplied. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Infrared reflectance measurements of a series of InN thin films have been performed and attempt to derive carrier concentration and other physical constants for InN thin film characterization. Fitting calculations are performed by use of the dielectric function equation based on phonon-plasmon coupling model. Longitudinal and transverse optical phonon frequencies, plasma frequency and their damping parameters can be derived from fitting. From those results, electrical and phonon properties of InN and characterization of films are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Films of InN have been grown on sapphire with a GaN buffer by the atmospheric-pressure MOVPE and the effects of GaN buffer etching with a KOH solution have been studied. With increasing etching time, the number of GaN grains is decreased and, as a result, the grain size of InN grown on the buffer is markedly increased. The grain size of InN grown on the 10 min-etched GaN buffer is larger than that of films grown without GaN buffer. When the GaN etching time is less than 5 min, the number of InN grains is smaller by about one order of magnitude than that of GaN buffer, showing that one InN grain is grown on about ten GaN grains on average. For the etching time of 8-10 min, the number of InN grains becomes approximately the same as that of GaN grains, indicating that under this condition one GaN grain acts as a nucleation center for one InN grain and no InN nucleation occurs in the areas without GaN grains on the sapphire substrate. The diffusion length of InN species on the sapphire substrate is estimated to be approximately 1 μm or more. In spite of the enhanced grain growth of InN films grown on the etched buffers, their electrical properties are a little worse compared with those grown without etching. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The electrical and optical properties for atmospheric-pressure MOVPE InN have been studied as a function of NH3/TMI molar ratio during the growth. Residual carrier (electron) concentration is decreased with increasing NH3/TMI molar ratio. PL peak energy is also shifted to a low energy side with increasing NH3/TMI molar ratio. Hall mobility of InN is almost independent on NH3/TMI molar ratio and is rather decreased at a high NH3/TMI molar ratio. The highest mobility is obtained for a sample grown at a relatively low NH3/TMI molar ratio. The grain size of the InN films is decreased with increasing NH3/TMI molar ratio. The lowest carrier concentration of 4.5×1018 cm–3 and highest mobility of 1100 cm2/Vs obtained here are the best data for MOVPE InN ever reported. Based on these results, the most probable candidate for donors and the dominant carrier-scattering mechanism for atmospheric-pressure MOVPE InN are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the MOVPE growth of InN on a 3c-SiC/Si template formed by C + -ion implantation into Si(lll). Properties of grown films on the template are compared with those grown on sapphire in the same run. By employing the nitridation process of the template at 900 °C for 30 min just before the GaN buffer growth, the buffer layer becomes to show uniform nucleation. This is due to the improved wettability of GaN layer on the template by the formation of Si-N bonds on the Si-polar SiC layer. The surface mophology of InN film grown on the nitrided template is similar to that for a film grown on a sapphire. The film on the nitrided template shows strong photoluminescence with a peak energy of 0.70 eV at room temperature. The carrier concentration and Hall mobility are 7.6 × 10 18 cm -3 and 630 cm 2 /Vs, respectively. These data are comparable to those for InN grown on the sapphire (0.71 eV, 6.5 × 10 18 cm -3 and 870 cm 2 /Vs). Thus, the nitridation process of the 3c-SiC/Si template is found to be effective to obtain high-quality InN film.

In this paper, the employment of the ArF excimer-laser assisted nitridation of sapphire substrate is studied in the ArF-laser assisted MOVPE (la-MOVPE) of InN. An ArF excimer laser with an energy 50 mJ/pulse and a repetition rate 20 Hz is introduced parallel to the substrate surface. The surface morphology of InN film grown on α-Al 2 O 3 (0001) is found to be markedly dependent on the nitridation conditions for the sapphire substrate. When no nitridation is made, the surface of grown InN film is very rough and many In droplets are found on it. A film with a mixture of rough-surface region with In droplets and smooth-surface region is grown on the thermally-nitrided substrate (1000 °C for 30 min). By employing the ArF-laser irradiation to the NH 3 flow during the substrate nitridation at 1000 °C for 30 min (la-nitridation), a smooth surface region is expanded to the entire surface of film. The smooth surface is found to be stable at growth temperature higher than 700 °C. The KOH etching of grown films reveals that the smooth surface has 5-10 time higher etching rate than the rough one. From these facts, it is concluded that the film with the smooth surface has N-polarity.

This paper reports the in-depth and in-plane inhomogeneities in InN films. Samples of InN are grown on sapphire substrates without or with a buffer using the atmospheric-pressure MOVPE. For the in-depth inhomogeneity analysis, the conventional PL measurement using an excitation source with a different wavelength is made from both the front surface and the film/substrate interface sides of samples. The measurement reveals that samples grown for a long time without buffer contain a deteriorated layer, which shows a higher PL peak energy, near the film/substrate interface. Such a layer is never found on the surface side. The deterioration is markedly enhanced when the sample is annealed in an NH 3 flow. Since the coexistence of TMI and NH 3 (growth environment) suppresses the deterioration and the InN samples used in this experiment have an In-polarity, such a deterioration is hydrogen-related degradation on the N-face of InN film. In-plane inhomogeneity of InN grown with a different buffer is studied by analyzing PL and absorption data. A wider PL spectrum and a larger discrepancy between PL peak energy and absorption edge, those are observed for films grown without buffer, are well explained by taking account of a large in-plane inhomogeneity in the samples. The existence of the large in-plane inhomogeneity is confirmed by the near-field PL mapping obtained by the SNOM. The SNOM analysis also shows that, although the use of the buffer improves the apparent in-plane uniformity, such a film has a fine inhomogeneity due to small grains of the buffer.

Aim: The incidence of ovarian cancer in Japan has increased since the 1970s. The many studies that have assessed the relationship between body mass index (BMI) and the risk of ovarian cancer have produced contradictory results. Here we investigated this relation using data from the Japan Collaborative Cohort Study for the Evaluation of Cancer Risk, which was initiated in 1988. Methods: A self-administered questionnaire on dietary habits and other risk factors for cancer was completed by 36 456 Japanese women. After 7.6 years of follow up, 38 cases of ovarian cancer were available for analysis. Cox proportional-hazards models were used to compute relative risks and to adjust for confounders. Results: Compared to women with BMI of 18.5–24.9 kg/m2, the relative risk of ovarian cancer was 2.24 (95% CI = 1.10–4.21) for BMI of 25.0–29.9 and 1.78 (95% CI = 0.24–13.34) for BMI of ≥ 30 kg/m2. A test for trend revealed that this finding was statistically significant (P = 0.014). Conclusion: The results of this study suggest that being overweight is independently associated with a higher risk of developing ovarian cancer in the Japanese population.

This paper reports a new interlayer for the epitaxial growth of InN on Si. A 3c-SiC layer as an interlayer is formed by carbon (C+)-ion implantation into Si(111) wafer. After the C+-ion implantation with an energy 180 keV at 600 °C, the Si(111) wafer is annealed in O2 atmosphere at 1250 °C for 2 h. Layers of SiO2, Si and polycrystalline SiC are successively removed and a single-crystalline 3c-SiC layer is exposed successfully on the surface. MOVPE growth of InN is performed at 600 °C on a 3c-SiC/Si(111) template with a low-temperature (550 °C) GaN buffer. The grown film is confirmed to be single-crystalline wurtzite InN by the RHEED patterns. The film shows an intense photoluminescence with peak energy of 0.73 eV at room temperature. Carrier concentration and Hall mobility are 1.3 × 1019 cm–3 and 490 cm2/Vs, respectively. They are slightly inferior to those for InN films grown on sapphire. The crystalline quality of InN is found to be improved with increasing the crystalline quality of the 3c-SiC layer formed by the implantation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An InN film is grown using an ArF excimer laser assisted-MOVPE where a high NH3 decomposition rate condition is realized because of the effective dissociation of NH3 by the ArF laser. Grown films show unusual phenomena such that amount of metallic In involved in a grown InN film is increased with increasing NH3 flow rate during the growth. Through the annealing of grown InN films in the NH3 flow, it is revealed that the photolysis of NH3 by the ArF laser irradiation causes the decomposition of InN and, as a result of it, the formation of In droplets. The direction of the source gases injection during the growth, perpendicular or parallel to the substrate surface, has a significant effect on the formation of metallic In. Compared with the perpendicular injection, the parallel injection can suppress the formation of In droplets and allow us to grow InN at a higher temperature. A high density of atomic hydrogen (H) generated by the photolysis of NH3 seems to take nitrogen atoms away from InN, leaving metallic In on the surface. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Background: Elevated mean corpuscular volume (MCV) is a traditional biological marker for alcohol abuse and alcoholism, but the underlying mechanism is unclear. Three recent epidemiologic studies consistently showed that MCV was elevated by alcohol drinking more markedly among individuals with genetically inactive aldehyde dehydrogenase-2 (ALDH2) (encoded by ALDH2*2 mutant allele) than those with active ALDH2 (encoded by ALDH2*1/2*1 genotype), suggesting that the elevated MCV was etiologically linked to acetaldehyde exposure. The purpose of the present study was to clarify further this relationship by examining the status of folate and vitamin B12. Methods: The study participants were 159 men who were aged 40 to 69 years and randomly selected from a Japanese rural population. The genetic polymorphism of ALDH2 was determined by PCR–restriction fragment length polymorphism method; data on alcohol drinking and other lifestyles were collected using a structured questionnaire; serum concentrations of folate and vitamin B12 were measured using the protein competitive reaction method, and blood cell counts were measured by routine methods. A multiple linear regression model was used to analyze the data. Results: The relationship between alcohol drinking and serum folate concentration was significantly different between ALDH2 genotypes, indicating that the reduction of serum folate by alcohol drinking was more marked in men with ALDH2*1/2*2 than those with ALDH2*1/2*1. The relationship between alcohol drinking and elevated MCV was significantly stronger in men with ALDH2*1/2*2 than those with ALDH2*1/2*1 even after adjustment for serum folate and vitamin B12 concentrations. Conclusions: These findings indicate that acetaldehyde plays a significant role in the development of decreased serum folate concentration and elevated MCV by alcohol drinking.

Aim: The many studies into the relation between cigarette smoking and the risk of ovarian cancer have produced inconsistent results. Here we investigated this relation using data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, initiated in 1988. Methods: A self-administered questionnaire on smoking habits and other risk factors for cancer was completed by 34 639 Japanese women. After 7.6 years of follow up, 39 cases of ovarian cancer were available for analyses. Cox proportional-hazards models were used to compute relative risks (RR) and to adjust for confounders. Results: Relative to those who had never smoked, the RR of ovarian cancer were 1.63 (95% confidence interval [CI] = 0.21–12.50) for former smokers and 2.27 (95% CI = 0.85–6.08) for current smokers. Among current smokers, the RR were 1.48 (95% CI = 0.20–10.92), 5.56 (95% CI = 1.68–19.06), and 1.86 (95% CI = 0.25–14.30) among women who smoked

We have investigated the Hall electron mobility of GaAsN and the InGaAsN as a function of temperature. The temperature dependence of the electron mobility for the GaAsN system cannot be explained by the alloy and the ionized impurity scattering mechanisms, and the experimental data indicate that unknown scattering mechanisms may be induced by the N incorporation. On the other hand, the temperature dependence for the InGaAsN system shows that the electron mobility improves in the low temperature range in contrast to the case of the GaAsN system. Moreover, the degradation of the mobility induced by the N incorporation is suppressed by the In incorporation, and the alloy scattering becomes dominant as the scattering mechanism in the InGaAsN system. The results strongly suggest that the scattering origin induced by the N incorporation for the GaAsN system may be related with the inhomogeneous N distribution and that the inhomogeneity may be suppressed by the In incorporation. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports In-doping effects in GaN films grown on Si(111) and α-Al2O3(0001) substrates using N2 carrier gas. By using the three step (350 °C, 450 °C and 550 °C) buffer layer growth process, single-crystalline GaN is obtained on Si(111) as well as on sapphire. From X-ray diffraction and RBS measurements it is revealed that the In incorporation in GaN films grown on Si is about 0.5%, whereas the level in GaN on sapphire is only 0.1%. The crystalline quality and optical properties for In-doped GaN on Si are scarcely improved in spite of the high In content. In-doped samples on Si show a very low excitonic emission peak energy (3.36 eV) because of both InGaN alloy formation and a high tensile stress caused by the hardening effect. In spite of the high tensile stress, the In-doped sample on Si(111) has very few cracks on the surface because of the hardening effect of GaN by In doping. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the effect of the GaN coating layer on the optical properties of GaN epilayers grown on GaAs/Si(111). Almost crack free GaN epilayers are found to be grown when a thin (∼25 nm) GaN coating layer is inserted on 0.5 and 2 μm GaAs layers at 550 °C. Then nitridation of the GaAs layer is done through the coating layer by NH3 flow while the substrate temperature is ramped at 1000 °C for epilayer growth. An attempt has also been made by implementing an additional GaN interlayer at 800 °C while growth is continued for epilayer growth. For this growth strategy, cracks also happened without improvement of the epilayer quality. PL measurements show high excitonic peak energy and high excitonic to yellow band intensity ratio for GaN epilayers grown on the 0.5 μm GaAs converted layer (CL) using a thin GaN coating layer. Those values are also found to be comparable/ better than for epilayers grown on 2 μm CL.

Systematic Raman scattering characterization for RF-MBE grown InGaAsN layers has been performed to investigate the preferential In–N bond formation. The present Raman results strongly indicate that the isolated In–N bonds have been preferentially formed mainly in the In-rich regions and that the growth temperature and the post-growth anneal cause some changes in the In–N bond formation in the InGaAsN layers. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present results of a detailed study of X-ray, photoluminescence, and Raman measurements of hexagonal InN, In-rich In x Ga 1-x N (0.36 < x < 1) alloys, and InN samples annealed in oxygen.

This paper reports on the catalyst-assisted metal-organic vapor phase epitaxy (CA-MOVPE) growth of InN with an independent control of catalyst temperature. When the catalyst temperature is increased above the growth temperature of InN, the grain size becomes large and full width at half maximum (FWHM) of X-ray rocking curve (XRC) is drastically decreased The migration of precursors is highly enhanced and the crystal quality is improved by CA-MOVPE with an independent heating system of the catalyst. This CA-MOVPE system will open the possibility of the growth of high-quality InN and In containing alloys especially with the higher In content (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this report we study the influence of the growth condition on the superconducting properties of InN grown on sapphire (0001). The samples are prepared by the use of MBE and MOCVD methods. The investigated InN has the mobilities of about 700 cm2 V–1 s–1 and the carrier concentrations of 6 × 1018 cm–3\sim 7 × 1019 cm–3}. The samples have clear hexagonal structure and distinct phonon structure with strong plasma reflections. The InN grown by these methods shows resistivity anomaly below 3.7 K and becomes type II superconductor at 0.5 K. The superconductivity of InN is anisotropic and its Hc1 and Hc2 depend on the angle between the field and the crystal c-axis. The involvement of metal In phase contributes to the characteristics of the superconductivity of InN.

Boiling KOH etching behavior of MOVPE GaN layer has been studied to understand the effects of substrate nitridation and carrier gas on its polarity. Relationships of the polarity between buffer and epitaxial layers are also studied. When H2 carrier gas is used, an epitaxial layer grown on a nitrided substrate shows a very low etching rate, i.e. Ga polarity, while the N polarity is dominant for that grown on a non-nitrided substrate. In both cases, the dominant polarity in the buffer and the epitaxial layer coincides each other. Buffer layers grown with N2 carrier gas grown on a nitrided substrate show a high dissolution rate as if N-polarity domains are dominant, although Ga-polarity epitaxial layers are grown on those buffer layers. This means that buffer layers grown with N2 carrier are of poor quality (defective).

Raman scattering and infrared absorption properties of RF-MBE grown AlGaAsN layers have been reported in order to investigate the microscopic lattice structures related with the nitrogen incorporation. Several new Raman modes of the Al-N bonds have been observed at 449, 500, and 650 cm -1 in the Raman spectra of AlGaAsN (Al: 18-100%, N: ∼2%) instead of the mode of Ga-N bonds. The results strongly indicated that most of the N atoms form the Al-N bonds in the AlGaAsN layers. The infrared absorption spectra of the AlGaAsN have shown clearly that the TO AlN mode appears at 500 cm -1 , instead of the TO GaN mode that appeared at 469 cm -1 in GaAsN. The peak shift and the broadening of the absorption peak of the TO AlN mode will be discussed in terms of variation of the statistical distributions of the Al n Ga 4-n N (n = 0, 1, 2, 3, 4) tetrahedral unit structures with increasing the Al amount.

A MOVPE InN film with a carrier concentration in the order of 10 18 cm -3 is successfully grown for the first time by using the atmospheric-pressure growth. Employing a reduced gas speed due to the atmospheric pressure and a reduced dilution N 2 gas flow rate, a carrier concentration of 5.8 × 10 18 cm -3 has been attained with a high electron mobility. The optimum growth temperature for the atmospheric pressure as well as reduced-pressure MOVPE growth is found to be around 600°C. It is found that sample with a relatively smooth surface has a mobility similar to the sample with lowest carrier concentration in spite of a relatively high carrier concentration, 730 cm 2 /V s, 2 × 10 19 cm -3 and 700 cm 2 /V s, 6 x 1018 cm -3 , showing that morphology is also one of the important factors to attain high electron mobility.

A survey of most recent studies of optical absorption, photoluminescence, photoluminescence excitation, and photomodulated reflectance spectra of single-crystalline hexagonal InN layers is presented. The samples studied were undoped n-type InN with electron concentrations between 6 × 10 18 and 4 × 10 19 cm -3 . It has been found that hexagonal InN is a narrow-gap semiconductor with a band gap of about 0.7 eV, which is much lower than the band gap cited in the literature. We also describe optical investigations of In-rich In x Ga 1-x N alloy layers (0.36 < x < 1) which have shown that the bowing parameter of b ∼ 2.5 eV allows one to reconcile our results and the literature data for the band gap of In x Ga 1-x N alloys over the entire composition region. Special attention is paid to the effects of post-growth treatment of InN crystals. It is shown that annealing in vacuum leads to a decrease in electron concentration and considerable homogenization of the optical characteristics of InN samples. At the same time, annealing in an oxygen atmosphere leads to formation of optically transparent alloys of InN-In 2 O 3 type, the band gap of which reaches approximately 2 eV at an oxygen concentration of about 20%. It is evident from photoluminescence spectra that the samples saturated partially by oxygen still contain fragments of InN of mesoscopic size.

This paper reports on the MOVPE growth of InN and InxGa1-xN with x up to ∼0.4 on AlN/Si (111) substrates. Good quality InN films are grown after a pretreatment of the substrate surface at 1000 °C in NH3. While pretreatment of the substrate surface in N2results the In droplet formation. Single-crystalline InxGa1-xN films with x up to ∼0.4 are successfully grown on Si (111) substrates without phase separation and metallic In incorporation by changing the growth temperature and TMI/(TMI+TEG) molar ratio. Comparative study between the AlN/Si (111) and GaN/α-Al2O3(0001) substrates shows that the quality of InN, GaN and InGaN with low In contents depends on the quality of the underlying layer. While the quality of InGaN at the intermediate In content range hardly depends on of the underlying layer/substrate. These works will allow us towards the fabrication of the future InGaN-Si tandem cell using MOVPE. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)