Search

The enhancement mode AlGaN/GaN hybrid MOS-HFETs on Si substrates have been demonstrated. The breakdown voltage of over 1.71 kV was achieved by investigating the epitaxial structure. Furthermore, a high integrity SiO2/Al2O3 gate stack has been demonstrated for GaN MOSFETs. The SiO2 film formed on GaN by the MW-PECVD exhibits good properties compared that by the LP-CVD. Then, by incorporating the advantages of both of SiO2 with a high insulating characteristics and Al2O3 with good interface characteristics, the SiO2/Al2O3 gate stack structure has been employed in GaN MOS devices. It is shown that a low interface state density between gate insulator and GaN, a high breakdown field, and a large charge-to-breakdown by applying 3-nm Al2O3 in this structure. The SiO2/Al2O3 gate stack has also been applied to AlGaN/GaN hybrid MOS-HFET and excellent properties with the threshold voltage of 4.2 V and the maximum field-effect mobility of 192 cm2/Vs are shown in the transistor.

The enhancement mode n-channel GaN-based MOSFETs on Si substrates have been demonstrated. We achieved a low interface state density between SiO2 and GaN, a high breakdown field, and a high reliability of SiO2 by annealing after SiO2 deposition on GaN. The SiO2 was applied for the gate oxide of GaN MOSFET. The fabricated GaN MOSFETs using an ion implantation technique showed good normally-off operation with threshold voltage of 2.7 V, the maximum output current of over 3.5 A, and a high-temperature operation up to 300oC. Furthermore, AlGaN/GaN hybrid MOS-HFETs were fabricated. The MOS-HFET has the merits of both a MOS channel and an AlGaN/GaN heterostructure with high mobility two dimensional electron gases. The maximum drain current of over 100 A was performed. The specific on-state resistance was 9.3 mΩ-cm2. The fabricated device also exhibited good normally-off operation and the breakdown voltage of over 600 V.

The paper reports a normally-off n-channel AlGaN/GaN hybrid metal–oxide–semiconductor heterojunction field-effect transistor (MOS-HFET) on Si substrate with high field-effect mobility. To decrease the channel resistance and to improve the field-effect mobility, of the MOS-HFET, a selective area growth (SAG) technique is applied at the channel region. The fabricated MOS-HFET exhibits a good normally-off operation with the threshold voltage of 3.7 V, the specific ON-state resistance of 7.6 mΩ cm2, and the breakdown voltage of over 800 V.

In this paper, GaN-based power transistors for a switching application were reported. In order to realize low loss and high power devices, GaN HFET structure on a Si substrate is a significant configuration as well as one of the cost-effective solutions. Furthermore, attempts for normally-off GaN-FETs were examined. A hybrid MOS-HFET structure is a promising candidate for obtaining devices with a lower on-resistance (Ron) and a high breakdown voltage (Vb).

In this paper, GaN power transistors on Si substrates for power switching application are reported. GaN heterojunction field-effect transistor (HFET) structure on Si is an important configuration in order to realize a low loss and high power devices as well as one of the cost-effective solutions. Current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate. Furthermore, attempts for normally off GaN-FETs were examined. A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance (Ron) and a high breakdown voltage (Vb).

GaN is promising for high-power, high-temperature devices due to its large bandgap, high critical electric field, and high saturation velocity compared with Si and SiC. The MOSFET structure can be operated at a positive threshold voltage, namely the normally-off mode, which is preferable for power transistors in terms of fail-safe operation. In order to realize MOSFET operation, good interface quality at SiO2/GaN and low resistance in the n+-contact layer is strongly required. We have overcome these requirements by precise thermal control. Finally, we have fabricated GaN MOSFETs and have achieved more than 1 A operation in the normally-off mode at more than 250oC. The breakdown voltage was more than 1500 V.

We report on the 288 V-10 V DC- DC converter circuit using AlGaN/GaN HFETs for the first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operation was fabricated. That is, the maximum drain current was over 50 A, and the minimum on-resistance was 70 mohm. The breakdown voltage was over 600 V. A DC-DC down-converter from input DC 288 V to output DC 10 V was fabricated using these HFETs. It was confirmed that the switching speed of the AlGaN/GaN HFET was faster than that of Si MOSFET. The DC-DC down-converter was fabricated using these HFETs. This converter was composed of a full bridge circuit using four n-channel AlGaN/GaN HFETs. In the case of AlGaN/GaN HFET, a gate switching wave (Vgs) and source-drain wave (Vds) were abrupt compared with those of using Si MOSFETs. In both cases, a stable and constant output DC 10V was also obtained and the conversion efficiency of the converters with AlGaN/GaN HFETs was 84%.

We developed new ohmic electrodes combined with an Al-silicide and a molybdenum for AlGaN/GaN HFETs to realize a high power switching application. As a result, the maximum drain current of the HFET was over 55 A and the breakdown voltage was about 800 V. The specific on-state resistance of the HFET was smaller than that of a Si Cool MOSFET. Furthermore, we examined the dynamic characteristics. The turn-off and turn-on delay time were 14.8 nsec. and 8.4 nsec. at the condition of 100 V, respectively. These values were considerbly smaller compared with those of Si Cool MOSFETs.

In order to obtain a high quality thick GaN layer on a 2-inch Si substrate without any crack, we investigated three kinds of buffer layer (AlGdN graded structure, AlN/GaN super lattice (SL) structure, and AIN/thick GaN/AIN structure) using a metal-organic chemical vapor deposition (MOCVD). As a result, we obtained a crack-free AlGaN/GaN hetero-structure with a smooth surface using three kinds of buffer structure. We also observed the cross-sectional TEM image of three kinds of buffer structures. In the case of using an AlGaN graded buffer on the AlN buffer, the number of surface defect with the size of 10000 nm was comparatively larger compared with the other buffer structures. In the case of using an AlN (18 nm)/ GaN (5 nm) super-lattice (SL) buffer, a 1000 nm-thick GaN was grown without crack. In the case of using three AlN (50 nm)/two thick GaN (200 nm) buffer structure, the threading dislocation using this buffer was 1.5 x 10 9 cm -2 and the value was smaller compared with the other buffer structures. This reduction effect of dislocation was larger than the other buffer structures. We also fabricated a HFET using the AlGaN/GaN heterostructure using three AlN/two thick GaN buffer. It was confirmed that the breakdown voltage of FET was over 400 V.

We demonstrate a novel field effect Schottky barrier diode (FESBD) with a dual Schottky structure combined with an AlGaN/GaN heterostructure to obtain a low on-voltage. The vertical and planar FESBDs were tried. A vertical AlGaN/GaN heterostructure was regrown by a selective area growth (SAG) technique using a metalorganic chemical vapor deposition (MOCVD). The contact layer was also grown using an SAG technique. Dual Schottky structures were fabricated to obtain a low on-voltage. That is, Al/Ti was used for a low Schottky barrier metal and Pt used for a higher barrier metal. The on-voltage of the diode was below 0.1 V. By the pinch-off effect of a higher Schottky barrier electrode, the reverse breakdown voltage was over 400 V although the Al/Ti used for a low Schottky barrier metal showed an ohmic property. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A normally-off FET is necessary for switching devices. We report on the enhancement operation GaN-based heterojunction field effect transistors (HFETs). The AlGaN/AlN/GaN heterostructure on a Si (111) substrate was grown using a metalorganic chemical vapor deposition (MOCVD). The HFET for a normally-off operation was fabricated using the AlGaN/C-GaN heterostructure. As a result, the HFET was operated at the condition of the positive gate bias. The breakdown voltage of FET was over 350 V. The on-state resistance (Ron) was about 10 mohmcm2. The maximum operation current of the FET was over 10 A. We also confirmed that the normally-off HFET was operated at 573 K. The normally-off operation of AlGaN/GaN HFETs on the Si substrate was thus confirmed for the first time. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on novel normally off GaN-based heterojunction field effect transistors (HFETs). An AlGaN/AlN/GaN heterostructure on a Si (1 1 1) substrate was grown using metalorganic chemical vapor deposition (MOCVD). The optimum growth condition of an Al X Ga 1− X N buffer for the formation of a thin homogeneous GaN layer on a Si (1 1 1) substrate was confirmed, and a high-quality AlGaN/GaN heterostructure for fabricating the HFET could be grown. It was suggested that an AlGaN buffer of Al incorporation replaced by Ga has an important role for obtaining a smooth surface. An AlGaN/C-doped GaN heterostructure was applied for an HFET with normally off operation for the first time. As a result, the HFET was operated under the condition of a positive gate bias. The breakdown voltage of the FET was over 300 V. The normally off HFET operation at 573 K was also evaluated. The normally off operation of GaN-based HFETs on a Si substrate was thus successfully confirmed.

In this paper, GaN-based HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. In order to improve a trade-off between the specific on-resistance (RonA) and the breakdown voltage (Vb), a combination of a thin uid (Un-Intentional Doped)-GaN layer and a thick carbon doped GaN layer as a back-barrier layer, resulting in an improvement of Vb without degrading on-state characteristics or current collapse (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

AlGaN/GaN HFETs with a large current and a high breakdown voltage were fabricated. We examined the switching characteristics and capacitance parameters such as an input capacitance (Ciss), a reverse transfer capacitance (Crss), a gate to a source charge (Qgs) and a gate to a drain charge (Qgd) using the GaN HFET devices. In order to confirm the advantage for the high-frequency switching operation of the GaN HFETs compared with Si devices, capacitance parameters and the figure of merit (FOM) Vb/(Ron) for a switching capability were examined. As a result, a low Ciss, Crss, and Qg were obtained and the FOMs of GaN HFETs have one order of magnitude larger than those of Si power devices. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We demonstrated the application of a power factor correction (PFC) circuit using AlGaN/GaN HFETs for the first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operation was fabricated. That is, the maximum drain current was over 50 A, and the minimum on-resistance was less than 70 mohm. The breakdown voltage was over 600 V. Using these HFETs, an AC-DC converter with a power factor correction (PFC) circuit was fabricated. Irregular input waves of AC current and voltage were converted to very smooth input sign waves of AC voltage and current. The power factor was over 99%. Using this circuit, AC 100 V was successfully converted to DC 200 V. the output conversion efficiency from AC input to DC output was 93%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study, normally-off GaN hybrid MOS-HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. As a result, the breakdown voltage (Vb) was improved using a combination of a high-resistive carbon-doped back barrier layer and a thin channel layer of 50 nm. The specific on-resistance (RonA) was estimated to be less than 7.1 mΩcm2 for Lgd = 12 μm, and Vb was estimated to be over 1.71 kV for Lgd = 18 μm. To our knowledge, these values are the best results ever reported for normally-off GaN-based MOSFETs.

Infinite-layer-type superconductors Sr 1− x Ln x CuO 2 are synthesized under high pressure of 3 GPa for Ln=Sm, Gd as well as for Ln=La, Nd. Their chemical and superconducting properties are systematically studied as functions of doping concentration and the kind of lanthanide ion. As a result, it is demonstrated that the variation of these properties with doping concentration is similar for all the examined Ln 3+ ions. The solubility limit lies at x ≈ 0.10. CuO 2 sheets are expanded with increasing x , while their spacing decreases. The T c onset determined by magnetic measurements remains constant for any doping concentration; only the Meissner fraction increases with increasing x .

High quality samples of both the alkaline-earth deficient type and the rare-earth substituted type of infinite-layered superconductors have been synthesized using a cubic anvil high-pressure apparatus. The result of oxygen content analysis by means of iodometry strongly supports the assertion that the A cation deficient phase can be either a p-type or an n-type superconductor, while the rare-earth substituted ones are n-type.

In this paper, GaN-based HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. As a result, the maximum drain current was estimated to be over 115 A using MIS-structures. A trade-off between the specific on-resistance (RonA) and the breakdown voltage (Vb) was improved using carbon doped buffer layers, resulting in obtaining RonA=3D 5.9 mΩcm2 and Vb=3D 1730 V simultaneously with the gate-width of a 340 mm. Furthermore, the gate field-plate structure was introduced into MIS-HFET structures. We have examined the suppression of a current collapse phenomenon owing to the combination of the gate field-plate structure and a conductive Si substrate with MIS-HFET devices.

GaN is promising for high-power, high-temperature devices due to some of its large bandgap, high critical electric field, and high saturation velocity compared with Si and SiC. The MOSFET structure can be operated at a positive threshold voltage in the normally-off mode, which is preferable for power transistors in terms of fail-safe operation. In order to realize MOSFET operation, low resistance in the n + -contact layer and good interface quality at SiO2/GaN are strongly required. We could reduce the interface state density at SiO2/GaN by annealing at 900 o C for 30 min. Furthermore, we successfully realized the formation of the n+ contact layer by annealing at 1260 o C for 30 s. Finally, we have fabricated GaN MOSFETs and have achieved more than 2.5 A operation in the normally-off mode at more than 250 o C. The breakdown voltage was more than 1550 V.

In this paper, GaN-based MIS-HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. As a result, the breakdown voltage was improved to be over 2.45 kV using high-resistive carbon doped buffer layers with a larger thickness of over 7.3 µm. The maximum drain current was estimated to be over 115 A using MIS-structures. A trade-off between the specific on-resistance (RonA) and the breakdown voltage (Vb) was improved using carbon doped buffer layers, resulting in obtaining RonA = 5.9 mΩcm2 and Vb = 1730 V simultaneously with the gate-width of a 340 mm. Furthermore, the field-plate structure was introduced into MIS-HFET structures. We have examined the suppression of a current collapse phenomenon owing to the combination of the gate field-plate structure and a conductive Si substrate with MIS-HFET devices.

In this paper, we successfully demonstrate an AlGaN/GaN HFET with a high breakdown voltage on 4-inch Si substrates. In order to obtain the high breakdown voltage and to improve the crystalline quality of GaN layers, a thick GaN epitaxial layer including a buffer layer was grown. The breakdown voltage and the maximum drain current were achieved to be over 1.3 kV and 120 A, respectively. Furthermore, the suppression of a current collapse phenomenon was examined. The on-resistance was not significantly increased up to a high drain off-bias-stress of 900 V. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A normally off AlGaN/GaN Hetero-junction Field Effect Transistor (HFET) structure is proposed. Two dimensional electron gas (2DEG) of more than 1 × 1013 cm–2, which a AlGaN/GaN HFET generally has, can be compensated completely by the negative charge in a floating gate or in a SiO2 layer on the AlGaN. Computer simulation showed that the threshold voltage was shifted from -3 V to -15 V with 20 nm SiO2 layer between the control gate and the AlGaN layer, but it was also shifted to +5V with 5 × 1013 cm–2 electrons (negative charge) in the middle of the SiO2 layer (a floating gate) or minus ions in the SiO2 layer itself. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Epitaxial growth technology for GaN devices on large-diameter Si substrate has been studied in this paper, which is essential for device cost reduction. In an effort to improve the buffer breakdown voltage for increasing the breakdown voltage of the device, carbon concentration in the GaN layer was controlled to find that the carbon concentration significantly contributed to buffer breakdown voltage improvements. Device performance was evaluated for the devices with an AlGaN/GaN HFET structure on Si substrate, and it was shown that the performance was equivalent to that of the device on sapphire substrate. A large-area device having this structure was fabricated in order to confirm its potential as a power device, and a current capacity of 120 A or more and a breakdown voltage of 1.8 kV were achieved. On the other hand, with respect to the problematical issue of current collapse in GaN HFETs, the HFET structure on Si substrate has resulted in a significant improvement compared with the structure on sapphire substrate, thus realizing a highperformance device that does not show a salient current collapse up to 1 kV.

Physical activity and dietary habits were compared between 80 men with adenomatous polyps of the sigmoid colon and 1148 men with normal colonoscopy among male retiring self-defense officials. Physical activity as expressed in terms of time spent doing strenuous activities during leisure time was inversely related to the risk of adenomatous polyps. Controlling for rank, smoking, alcohol and body mass index (BMI), odds ratios for the categories of 0, 1-59, 60-119 and greater than or equal to 120 minutes per week were 1.0, 0.88, 0.70 and 0.44, respectively (trend p = 0.015). Among a limited range of foods and beverages, the consumption of rice, green tea and instant coffee tended to be associated with a decreased risk of adenomatous polyps. Although the associations observed with dietary habits still need to be substantiated, the findings on physical activity lend further evidence to the hypothesis that physical activity may be protective in the development of colon cancer.

In this paper, we successfully demonstrate an AlGaN HFET with a high breakdown voltage of over 1.8 kV on 4 inch Si substrates. In order to obtain the high breakdown voltage and to improve the crystalline quality of GaN layers, a thick GaN epitaxial layer including a buffer layer with a total thickness of over 6 mum was grown. The breakdown voltage and the maximum drain current were achieved to be over 1.8 kV and 120 A, respectively. Furthermore, the suppression of the current collapse phenomenon is examined. The on-resistance is not so significantly increased up to the high drain off-bias-stress of 1.0 kV.

The drinking habits of 86 men with adenomatous polyps of the sigmoid colon were compared to those of 1184 men with normal colonoscopy among middle-aged male self-defence officials. After adjustment for rank, smoking history and rice consumption, total ethanol intake was positively associated with the risk of adenomatous polyps. The odds ratio (OR) was 2.4 (95% confidence interval (CI) 1.0-5.5) for men consuming at least 60 ml of ethanol per day. Among five alcoholic beverages (shochu, beer, sake, whiskey and wine), both sake and beer showed a dose-response relationship with the risk of adenomatous polyps although the association with beer was less striking. Shochu was the largest source of ethanol intake in the study population, but there was virtually no association between shochu consumption and adenomatous polyps. Men drinking wine had a significantly increased risk, but these men were too few to examine the relation in detail. The findings suggest that the consumption of specific alcoholic beverages rather than ethanol itself is associated with an increased risk of adenomatous polyps of the sigmoid colon.

Colorectal adenoma is regarded as a precursor lesion of adenocarcinoma. In view of the controversy on serum cholesterol and colorectal cancer, the risk of colorectal adenoma was examined in relation to serum total cholesterol, triglycerides and HDL-cholesterol. In the comparison of 88 men having adenoma and 1055 men with normal colonoscopy, there was no association between serum total cholesterol and colorectal adenoma. An increased risk of adenoma was observed at the highest quartile of triglycerides and at the lowest of HDL-cholesterol. When the three serum lipids were simultaneously examined, only the relation with HDL-cholesterol remained unchanged giving odds ratio of 1.7 at the lowest quartile compared with the upper three combined (p less than 0.05). The present study is consistent with the view that the inverse relation between serum total cholesterol and colorectal cancer is due to the effects of preclinical cancer. Further clarification is needed on low HDL-cholesterol and colorectal adenoma.

The induction heating (IH) system with a soft switching was fabricated using AlGaN/GaN heterojunction field effect transistors (HFETs). The operation current and breakdown voltage of an AlGaN/GaN HFET were over 50 A and 800 V, respectively. The specific on-resistance was 10 mOmegacm2. The turn-on and turn-off time were less than 20 ns, respectively. We fabricated the IH system with a soft switching circuit which can be driven using normally-on AlGaN/GaN HFETs. The IH system with a soft switching using normally-on AlGaN/GaN HFETs was demonstrated for the first time. Then output power was 3.2 kVA.

Improved characteristics of an AlGaN/GaN HFET are reported. We introduced new fabrication processes using Ti/AlSi/Mo ohmic electrode and a low refractive index SiNx to decrease the contact resistance and gate leakage current. The AlGaN/GaN HFET showed low a specific resistance of 6.3 mOmegacm2 and a high breakdown voltage of 750 V. We investigated switching characteristics of an AlGaN/GaN HFET. The small turn-on delay of 7.2 nsec, which was 1/10 of Si MOSFET, was measured. The switching operation of the HFET showed no significant degradation up to 225degC

We investigated an AlGaN/GaN heterostructure field effect transistor (HFET) on Si substrates using a multi-wafer metalorganic vapor phase epitaxy (MOVPE) system. It was confirmed that a GaN film with smooth surface and without any crack was obtained. To increase a resistance of a GaN buffer layer, the carbon (C) -doping was carried out by controlling the V/III ratio and the growth pressure. The breakdown voltage of the buffer layer was dramatically improved by introducing the C. As a result, the breakdown voltage was about 900 V when the C concentration was about ∼8×1018 cm−3. After while, an AlGaN/GaN heterojunction FET (HFET) on a C-doped GaN buffer layer was fabricated. We achieved the breakdown voltage of over 1000 V and the maximum drain current of over 150 mA/mm, respectively. It was found that the C doped buffer layer is very effective for improving the breakdown voltage of AlGaN/GaN HFETs.

It is reported that we demonstrated a large current operation AlGaN/GaN HFET with a low-on state resistance and a high breakdown voltage operation at room temperature and 500 K. We developed our unique ohmic electrode using Ti/AlSi/Mo. In addition, we investigated the dependence between the distance from the gate electrode to the drain electrode and the off-state breakdown voltage. As a result, the breakdown voltage of a unit HFET was over 1100 V. Furthermore, on the large scale HFET with the gate width of 240 mm, the maximum drain current of over 50 A was obtained at room temperature and also, that of over 25 A was obtained at 500 K. The off-state breakdown voltage was obtained about 800 V at room temperature and about 600 V at 500 K, although Si-based FETs can not operate in such a high temperature.

We investigated an AlGaN/GaN Schottky barrier diode (SBD) with a field plate structure for a high breakdown voltage. The AlGaN/GaN heterostructure was grown by MOCVD. The AlGaN buffer was grown on the Si (111) substrate and Al0.25Ga0.75N (25 nm)/ GaN (1000 nm) was grown on the buffer layer. The AlGaN/GaN heterostructure without any crack was obtained. After that, a Schottky barrier diode was fabricated using an AlGaN/GaN heterostructure. In order to obtain a high breakdown voltage, a gate field plate structure was used. SiO2 was formed on the AlGaN layer using a plasma chemical vapor deposition. The Schottky electrode of Ni/Au was partially deposited on the SiO2 film towards the ohmic region. The length of field plate structure was also changed to investigate the effect. Ti/Al-silicide was used for an ohmic electrode of SBD. The contact resistance of ohmic electrodes was 8E-6 ohmcm2.The current-voltage characteristics of an AlGaN/GaN SBD were measured. The reverse breakdown voltage of the diode was also over 1000 V and the reverse leakage current was below 1.5E-6 A/mm.

We report on the novel normally-off GaN-based heterojunction field effect transistors (HFETs) on a Si substrate. The AlGaN/AlN/GaN heterostructure was grown using a metalorganic chemical vapor deposition (MOCVD). The HFET for a normally-off operation was fabricated using a precisely controlled thin-AlGaN layer as an electron supply layer. As a result, the HFET was operated at the condition of the positive gate bias. We also characterized the enlarged gate-width devices. The breakdown voltage of FET was over 300 V. A normally-off operation using GaN based HFETs with a thin-AlGaN/AlN/GaN heterostructure on the silicon substrate were thus confirmed for the first time.

ABSTRUCT:We have proposed a novel field effect Schottky barrier diode (FESBD) with a dual Schottky structure combined with an AlGaN/GaN heterostructure in order to obtain a very low on-voltage. This diode has a dual Schottky structure of a very low Schottky barrier metal and a high Schottky barrier metal for obtaining a low on-voltage. The leakage current at a reverse bias was suppressed by the pinch-off based on field effect of a higher Schottky barrier metal, resulting in increasing the reverse breakdown voltage.In this paper, we carried out a planer-type FESBD for a large current operation. The AlGaN/GaN heterostructure was grown by a metalorganic chemical vapor deposition (MOCVD). A dual Schottky structure was fabricated using Ti/Al and Pt. An ohmic electrode was also Ti/Al. As a result, the on voltage of FESBD was below 0.1 V. The reverse breakdown voltage was also over 400 V by pinch-off effect. The switching time of the diode was shorter than 3 ns.

not Available.

Risk factors of gallstone disease were investigated in male self-defense officials who received, between October 1986 and December 1990, a retirement health examination at the Self-Defense Forces Fukuoka Hospital, Fukuoka, Japan. Gallbladder ultrasonography, successfully performed with 2,739 of 2,756 men, found 61 men with gallstones and 38 men with previous removal of the gallbladder; the overall prevalence of gallstone disease was 3.6%. Multiple logistic regression analysis assessed the risk of gallstone disease in relation to smoking, alcohol use, body mass index, glucose tolerance, and rank. Alcohol use was associated with a decreased risk, and body mass index was positively related to gallstone disease. Men with impaired glucose tolerance had a slightly elevated risk, whereas diabetes mellitus was not associated with gallstone disease. Analysis for prevalent gallstones and the postcholecystectomy state showed an inverse association of alcohol use with the latter; a positive association with impaired glucose tolerance was also confined primarily to the latter condition. These findings provide little support for a protective effect of alcohol use in the formation of gallstones. It was inconclusive whether impaired glucose tolerance was associated selectively with postcholecystectomy.

METHODS. The relation between green tea consumption and serum lipid concentrations was examined using cross-sectional data on 1,306 males who received the retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and December 1988. RESULTS. After adjustment for rank, smoking, alcohol use, physical activity, and body mass index, serum total cholesterol levels were found to be inversely related to the consumption of green tea while no association was noted with serum triglycerides and high-density lipoprotein cholesterol. Adjusted mean concentrations of total cholesterol were 8 mg/dl lower in men drinking nine cups or more per day than in those consuming zero to two cups per day. Serum cholesterol levels were inversely associated with traditional Japanese dietary habits (intake of rice and soy bean paste soup) and positively associated with Westernized habits. Additional adjustment for these dietary variables did not alter the inverse relation between green tea and total cholesterol.