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The efficacy of once-weekly risedronate with and without cholecalciferol in bone mineral density (BMD) in Korean patients with osteoporosis was compared. After 12 months, both spine and hip BMD increased significantly in both groups, but there was no significant difference between two groups. This study investigated the efficacy and safety of once-weekly risedronate with and without cholecalciferol in BMD in Korean patients with osteoporosis. This was a prospective, 12-month, randomized, open-labeled, actively controlled trial involving 41 hospitals. A total of 841 subjects with osteoporosis were randomized to once-weekly risedronate (35 mg) and cholecalciferol (5600 IU) in a single pill (RSD+, n = 642) or once-weekly risedronate (35 mg) alone (RSD, n = 199). BMD was measured via dual-energy X-ray absorptiometry at the lumbar spine and hip, and the serum levels of 25-hydroxy vitamin D (25(OH) D), parathyroid hormone (PTH), and alkaline phosphatase (ALP) were assayed at baseline and after 12 months of treatment. After 12 months, the lumbar spine, femoral neck, and total hip BMD increased significantly in both groups; there was no significant difference between two groups. Women in the RSD+ group exhibited significantly increased lumbar spine BMD, and subjects with previous fracture history in the RSD+ group had significantly increased total hip BMD compared with the RSD group. The serum 25(OH) D level increased significantly in the RSD+ group. The serum PTH level decreased in the RSD+ group but increased in the RSD group. The serum ALP level significantly decreased in both groups; there was no significant difference between two groups. A once-weekly pill containing risedronate and cholecalciferol had the equivalent antiresorptive efficacy on BMD compared with risedronate alone and improved 25(OH) D serum levels after 12 months of treatment without significant adverse events in Korean patients with osteoporosis.

Summary Background Light-emitting diode (LED) phototherapy and water bath therapy have beneficial effect on atopic dermatitis (AD)-like skin disease. However, not all current treatments work well and alternative therapies are need. The contribution of combination therapy with low-dose 850 nm LED and water bath was investigated on dermatophagoides farina (Df)-induced dermatitis in NC/Nga mice. Methods Low-dose LED (10, 15, and 20 J/cm2) irradiation, water bath (36 ± 1°C) were administered separately and together to the Df-induced NC/Nga mice in acrylic jar once a day for 2 weeks. Results Combined therapy with low-dose LED therapy and water bath therapy significantly ameliorated the development of AD-like skin lesions. These effects were correlated with the suppression of total IgE, NO, histamine, and Th2-mediated immune responses. Furthermore, combination therapy significantly reduced the infiltration of inflammatory cells and the induction of thymic stromal lymphopoietin (TSLP) in the skin lesions. The beneficial therapeutic effects of this combination therapy might regulate by the inhibition of various immunological responses including Th2-mediated immune responses, inflammatory mediators such as IgE, histamine, and NO, as well as inflammatory cells. Conclusions The combination therapy of LED and water bath might be used as an efficacious, safe, and steroid-free alternative therapeutic strategy for the treatment of AD.

Background: The aim of this study was to describe sectioned images and stereoscopic anatomic models of the maxillofacial area by using Visible Korean which are beneficial for medical education and clinical training in the field of orthognathic surgery. Materials and methods: Serially sectioned images of the maxillofacial area of a cadaver were created. Significant structures in the sectioned images were outlined and stacked to build surface models. Results: Browsing software (95.1 MB) and portable document format (PDF) file (142 MB) that were constructed are freely downloadable from our website (http://anatomy.co.kr). In the browsing software, the names of structures associated with malocclusion and orthognathic surgery could be viewed on the sectioned images. In the PDF file, surface models and stereoscopic maxillofacial structures were displayed in real-time. Conclusions: The state-of-the-art sectioned images, outlined images, and surface models that were arranged and systematised in this study, may help students and trainees investigate the anatomy of the maxillofacial area for orthognathic surgery.

In this article, we report the first observation of unipolar memory effect in Al/ZnO NR/Al planar devices. ZnO nanorods were synthesized using facile solution route at room temperature. The synthesized nanorods were characterized by X-ray diffraction and scanning electron microscope. Using the synthesized ZnO nanorods two terminal planar devices were fabricated with lithographically defined metal contacts. The constructed metal-ZnO-metal devices have exhibited unipolar resistive memory characteristics with rectification and NDR effects. Mechanism for the unipolar switching has been proposed based on the formation and rupture of AlOx interlayer in the metal-semiconductor interface. The simultaneous occurrence of rectification and NDR effects with switching property has also been explained. This article brings an innovative and easy fabrication of unipolar resistive switching devices.

A 6–18 GHz, 8.1 W gallium nitride (GaN) distributed amplifier (DA) monolithic microwave integrated circuit (MMIC) is presented with compact size. To accomplish high-output power density with compact size, the last two sections of the DA consist of small-sized FETs. This approach improves the output return loss and allows the drain line lengths to be reduced thereby increasing the drain cut-off frequency and reducing circuit size, which results in increased gain and output power characteristics up to higher frequencies. Source via holes of GaN high electron mobility transistors (HEMTs) are also shared to reduce chip size. The proposed DA is implemented as a two-stage DA using a commercial 0.25 µm GaN MMIC process. It shows 8.1 W average continuous wave output power and 6.8 dB average associated gain from 6 to 18 GHz under 36 V drain bias with 6.7 mm2 chip area. The proposed DA obtains 1.21 W/mm2 output power density and 1.02 dB/mm2 gain density.

This paper demonstrates normally-off dual gate AlGaN/GaN MISFETs with a selective area-recessed floating gate fabricated on the AlGaN/GaN-based heterostructure with an AlN insertion layer. For the fabrication of the dual gate structure, the AlGaN layer in the control gate region was fully recessed and then an Al2O3 layer as a gate dielectric was deposited by the atomic layer deposition method, which ensures the normally-off operation and greatly decreases the leakage current. An additional floating gate with selective area-recessed patterns, which is located between the control gate and the drain electrode, was employed to enhance the breakdown voltage. The fabricated normally-off dual gate AlGaN/GaN MISFET exhibited a threshold voltage of 2 V, a high ION/IOFF ratio of 3 × 108 at a drain voltage of 10 V, a maximum transconductance of 88 mS/mm at a gate voltage of 5.8 V, a drain current density of 364 mA/mm at a gate voltage of 8 V, and a breakdown voltage of 880 V.

We report the observation of negative differential resistance (NDR) in solution synthesized ZnO nanorod. The ZnO nanorod was fabricated as a two terminal planar device using lithographically patterned Au electrodes. The measured current–voltage response of the device has shown a negative differential resistance behavior. The peak-to-valley current ratio of the NDR is found to be greater than 4. The mechanism of this observed NDR effect has been explained based on charge trapping and de-trapping at the nanoscale contacts. It is the first observation of negative differential resistance effect in solution synthesized ZnO nanorod.

We report the fabrication and DC and microwave characteristics of 0.5 μm AlGaN/GaN high electron mobility transistors using double plasma treatment process. Silicon nitride layers 700 and 150 A thick were deposited by plasma-enhanced chemical vapor deposition at 260 °C to protect the device and to define the gate footprint. The double plasma process was carried out by two different etching techniques to obtain enhancement-mode AlGaN/GaN high electron mobility transistors with 0.5 μm gate lengths. The enhancement-mode AlGaN/GaN high electron mobility transistor was prepared in parallel to the depletion-mode AlGaN/GaN high electron mobility transistor device on one wafer. Completed double plasma treated 0.5 μm AlGaN/GaN high electron mobility transistor devices fabricated by dry etching exhibited a peak transconductance, gm, of 330 mS/mm, a breakdown voltage of 115 V, a current-gain cutoff frequency ( f T ) of 18 GHz, and a maximum oscillation frequency ( f max ) of 66 GHz.

In this paper, we propose a superjunction trench gate MOSFET (SJ TGMOSFET) fabricated through a simple p-pillar forming process using deep trench and boron silicate glass doping process technology to reduce the process complexity. Throughout the various boron doping experiments, as well as the process simulations, we optimize the process conditions related with the p-pillar depth, lateral boron doping concentration, and diffusion temperature. Compared with a conventional TGMOSFET, the potential of the SJ TGMOSFET is more uniformly distributed and widely spread in the bulk region of the n-drift layer due to the trenched p-pillar. The measured breakdown voltage of the SJ TGMOSFET is at least 28% more than that of a conventional device.

A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single-mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time-domain transfer-matrix-based laser model is developed. Based on this model, we perform steady-state and large-signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10-Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.

In this research, a stand-alone camel-gate (⌝) head structure has been studied to investigate the effects of the field plate (FP) in the source access region in AlGaN/GaN high-electron-mobility transistors (HEMTs). The camel gate serves as an FP toward the source side. Using this concept of the camel gate, the transconductance and other forward characteristics have been analyzed with regard to the T-gate. The recessed camel-gate FP scaling is confirmed to enhance the breakdown voltage, transconductance, and output current by reducing the electric field, leakage current, and dispersion in the source access region. Further, the optimized recessed camel-gate AlGaN/GaN HEMT is suitable for use in RF devices because it exhibits a frequency on the order of gigahertz.

A method to improve isolation characteristics of internal MIMO antenna systems for wireless portable devices operating in the GHz band is presented. The proposed system incorporates multiple pairs of L-slots between the two antennas in the ground plane, which operate like a band-stop filter, suppressing mutual coupling between the antennas and resulting in improved isolation. A MIMO antenna system with 6 pairs of L-slots shows reflection loss of -26.4 dB and isolation of -37.5 dB.

In this paper, we have presented millimeter-wave high conversion gain quadruple subharmonic mixers adopting the cascode structure. The subharmonic mixers were successfully integrated by using 0.1 μm GaAs pseudomorphic HEMTs (PHEMT's) and the coplanar waveguide (CPW) structures. From the measurement at LO power of 13 dBm at 14.5 GHz, it shows that conversion gain is 3.4 dB which is one of the best conversion gains at 60.4 GHz. Isolations of LO-to-IF and LO-to-RF were −53.6 dB and −46.2 dB, at a frequency of 14.5 GHz, respectively.

This study was designed to investigate the effect of Zen Meditation on serum nitric oxide activity (NO) and oxidative stress (lipid peroxidation). The experimental group included 20 subjects who had practiced the Zen Meditation program in Meditation Center located in Seoul, South Korea. The control group included 20 subjects who did not practice any formal stress management technique and were age and sex matched with experimental group. To provide an assessment of nitric oxide production, the serum level of nitrate/nitrite was determined using the Griess reagent. Malondialdehyde (MDA) concentration was measured as a convenient index of lipid peroxidation by thiobarbituric acid (TBA) method. Meditation group showed a significant higher level of serum nitrate+nitrite concentration and a significant reduced level of serum malondialdehyde (MDA) than control group. A comprehensive randomized controlled trial should be performed to prove the causal relationship between meditation and level of nitric oxide or oxidative stress in reducing cardiovascular risk factors.

In this paper, a millimeter-wave ×4 subharmonic mixer has been designed and fabricated. The cascode 4th-harmonic generator is proposed for high conversion gain. The measurement of an LO power of 13 dBm shows a conversion gain of 3.4 dB, which is one of the best conversion gains at 60.4 GHz. Isolations of LO to IF and LO to RF were obtained −53.6 and −46.2 dB, respectively. The high conversion gain achieved in this work is the first to be reported among millimeter-wave subharmonic mixers. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 490–493, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20181

In this paper, we present a high performance V-band quadruple sub-harmonic mixer monolithic circuit which is designed and fabricated for the millimeter wave down converter applications. While the typical sub-harmonic mixer use a half of fundamental frequency, we adopt a quarter of the fundamental frequency. The proposed circuit is based on typical sub-harmonic mixer with anti-parallel diode pair (APDP). Upon the typical mixer design, additional stubs are placed with the modification of original stub length. The stubs, 0.1 μm pseudomorphic high electron mobility transistors (PHEMTs) and other components are appropriately positioned to each port for maximizing quarter frequencies. Maximum conversion gain of 0.8 dB at a LO frequency of 14.5 GHz and at a RF frequency of 60.4 GHz is measured. Both LO-to-RF and LO-to-IF isolations are higher than 40 dB. The achieved result of conversion gain and isolation characteristic is one of the best performances reported among the quadruple sub-harmonic mixer operating in the V-band millimeter wave frequency.

A high-performance V-band quadruple subharmonic mixer monolithic circuit is fabricated using the millimeter-wave monolithic integrated circuit (MIMIC) process. Due to the superior features of the anti-parallel diode pair (APDP) and the utilization of a quarter of fundamental frequency, the proposed subharmonic mixer shows good conversion-gain and isolation characteristics. Maximum conversion gain of 0.8 dB at an LO frequency of 14.5 GHz and an RF frequency of 60.4 GHz is measured. Both LO-to-RF and LO-to-IF isolations are higher than 50 dB in the operation mode. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 349–352, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11378

We examine the effects of thin-film passivation on the DC, RF and noise characteristics of 0.1-µm-gate-length pseudomorphic high-electron-mobility transistors (PHEMTs) when either conventional Si3N4 or low-dielectric-constant benzo-cyclo-butene (BCB) is used for the passivation layer. A significant shift in pinch-off voltage of ~-0.4 V is observed from the PHEMTs after the Si3N4 passivation, whereas no such variation in DC parameters is observed in the case of BCB passivation. Noise figures of the devices are very stable after the BCB passivation and are only ~60% of those in the case of Si3N4 passivation when measured at 55–62 GHz. Other RF parameters are not significantly affected by the passivation materials at a frequency of 50 GHz. We propose that the degradation in DC and noise characteristics can be due to the high density of surface states in the Si3N4 passivation layers; on the other hand, excellent stability in electrical characteristics in the BCB passivations can attribute to the minimized surface states in the passivation layer.

We demonstrate a 10-Gb/s tunable external cavity laser with a polymer Bragg reflector and a highly integrated semiconductor gain chip including an asymmetric ring resonator reflector. The output power of the tunable laser is increased by adjusting the coupling strengths of two multimode interferences (MMIs) of the ring resonator reflector. The output power of the tunable laser is 6 mW at gain and semiconductor optical amplifier currents of 100 mA, and at a temperature of 25°C when the cross-coupling strengths ratios of two MMI couplers are 0.36 and 0.5. The tunable laser successfully provides 10-Gb/s transmissions through 20-km standard single mode fiber (SMF). The power penalty of the tunable laser is less than 2 dB after a 20-km SMF transmission for a 16-nm tuning range. The power penalty variation is less than 2 dB during the blue-shifted wavelength tuning.

We report on a novel combination of measurement techniques for evaluating dimensional and compositional changes of selective-area-grown multiple-quantum-well laser diodes (SAG MQW LDs). This technique is based on C-V and I-V measurements of the fully fabricated LDs. Using this technique, the changes in the capacitance and voltage correspond to the layer thickness and bandgap energy. To verify the effectiveness of the proposed technique, we first fabricated an LD array containing ten different SAG MQW structures, and examined the effects of the dimensional and compositional changes on the wavelength shift both theoretically and experimentally. From our examination, we found that a wavelength shift of 83 nm is obtained for an SAG mask pattern with an opening width of 100 mu m, and that a cross point between both dimensional and compositional changes exists for this mask pattern. As the following step, the fabricated LD array was tested using the proposed technique, and the growth rate enhancement and bandgap energy were extracted from the measured C-V and I-V results. The extracted data for each array channel were compared with the simulation results, which were well-fitted from the photo-luminescence (PL) measurements. They both show good agreement with the simulation results. (C) 2014 Optical Society of America

Surface quality and optical reflectivity of the hot-Al/Ti interconnecting metal layers show a strong dependence on the surface condition of the underlying inter-metal dielectric oxides (IMDs). When hot-Al/Ti films are deposited by a two-step method, a much lower (0002) Ti X-ray diffraction is obtained from the hydrophilic oxide substrates than from the hydrophobic ones. This Ti film crystalline structure affects (111) diffraction and surface roughness of the Al interconnecting films. An optimized RF pre-cleaning process prior to the Al/Ti deposition enhances the smoothness and hydrophobic surface property of the IMDs, as measured by atomic force microscopy and sessile drop contact angle method, and greatly improves aluminum surface quality. Etch yield of the interconnect lines is monitored at 0.4/0.4 μm bridge test patterns of 3.5 mega-bit arrays, and is greatly influenced by the surface condition of underlying IMDs.

Current crowding effect is detrimental for the performance of light-emitting diodes (LEDs), causing non-uniform light emission and local heat generation. In particular, heat generated by non-uniform current distribution can badly influence the performance of LED devices. In this paper, we examine the temperature distributions of lateral InGaN/GaN multiple-quantum-well LEDs in relation to current crowding, using both simulation and experimental results. Simulation results are obtained from a 3-dimensional electrical circuit model consisting of resistances and intrinsic diodes. Temperature and luminance distributions are investigated by images taken by an infrared camera and a charge-coupled-device camera, respectively. Finally, the internal quantum efficiency is taken for each device and compared. We show that the thermal property in the lateral LED is affected by the current crowding due to the local Joule heating nearby electrodes. Therefore, uniform current spreading is very important not only for uniform luminance distribution but also for good thermal property in the LED device. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The quaternary compound, Al x Ga y In 1 − x − y As ( x + y = 0.47−8) lattice-matched to InP substrates was realized as a buffer layer in an InP-based lattice-matched high electron mobility transistors. The band gap energy of this quaternary compound buffer layer was linearly decreased from E g = 1.54 eV for Al 0.48 Ga y =0 In 0.52 As to E g = 0.82 eV for Al x =0 Ga 0.47 In 0.53 As by varying Al and Ga mole fraction simultaneously. A self-consistent analysis revealed, one, that this buffer layer modified the quantum-well structure into a triangular-shaped conduction-band profile and, two, the disappearance of the quantum-well in valance-band profile. By forming a triangular-shaped conduction-band quantumwell, carrier wave functions drifted farther apart from the heterointerface, leading to the reduction of ionized impurity scattering. Disappearance of holes in a valance band also contributed to the reduction of the hole and electron recombination scattering. A high electron mobility of 11 338 cm 2 /V s with two-dimensional electron gas density of 2.5 × 10 12 /cm 2 was achieved at room temperature. The high electron mobility was believed to have resulted from the modified triangular-shape quantum well in which the ionized impurity ion scattering was suppressed. We believe that we have achieved the highest room temperature value of electron mobility time with two-dimensional electron gas concentration that was 2.83 × 10 16 /cm 2 to date for InP-based lattice-matched high electron mobility transistors system. PL measurement showed some evidences of a high-quality epitaxial growth.

We report high switching performance of 0.1-/spl mu/m metamorphic high-electron mobility transistors (HEMTs) for microwave/millimeter-wave monolithic integrated circuit (MMIC) resistive mixer applications. Very low source/drain resistances and gate capacitances, which are 56 and 31% lower than those of conventional pseudomorphic HEMTs, are due to the optimized epitaxial and device structure. Based on these high-performance metamorphic HEMTs, a 94-GHz MMIC resistive mixer was designed and fabricated, and a very low conversion loss of 8.2 dB at a local oscillator power of 7 dBm was obtained. This is the best performing W-band resistive field-effect transistor mixer in terms of conversion loss utilizing GaAs-based HEMTs reported to date.

InxGa1 − xAsInyAl1 − yAs heterostructure with both high electron mobility and high carrier concentration has been fabricated on InP substrate by molecular beam epitaxy. The measured electron mobilities were 11 491 cm2/V · s at 300 K and 53 316 cm2/V · s at 77 K for two-dimensional electron gas concentrations of 4.7 × 1012 and 3.5 × 1012 cm−2, respectively. The high electron mobility and concentration resulted from the dislocation-free, relatively thick (200 A), and high indium content (80%) channel layer. The high-quality InxGa1 − xAs channel layer was successfully grown at a growth temperature of 520°C after introducing a linearly graded InyAl1 − yAs buffer structure grown at a reduced growth temperature of 420°C. The cross-sectional transmission electron microscopy observation revealed that the dislocations generated due to a large lattice mismatch between InyAl1 − yAs and InP substrate were locked up in the middle of the graded buffer layer. We believe that we have achieved to date for this materials system the highest room-temperature conductivity (mobility times carrier concentration) of 5.4 × 1016/V · s.

A high-efficient GaAs power metal semiconductor field effect transistor operating at a drain voltage of 2.3 V has been developed for low distortion power applications. The device has been fabricated on an epitaxial layer with a high-low doped structure grown by molecular beam epitaxy. The MESFET with a gate length of 0.8 /spl mu/m and a total gate width of 21.16 mm showed a maximum drain current of 5.9 A at V/sub gs/=0.5 V, a knee voltage of 1.0 V and a gate-to-drain breakdown voltage of 28 V. The MESFET tested at a 2.3 V drain bias and a 900 MHz operation frequency displayed the best power-added efficiency of 68% with an output power of 31.3 dBm. The associate power gain at 20 dBm input power and the linear gain were 11.3 dB and 16.0 dB, respectively. The power characteristics of the device operating under a bias of 2 V exhibit power-added efficiency of 67% and output power of 30.1 dBm at an input power of 20 dBm. Two tone test measured at 900.00 MHz and 900.03 MHz shows that 3rd-order intermodulation and power-added efficiency at an output power of 27 dBm were -30.6 dBc and 36%, respectively, which are good for CDMA digital applications. A third-order intercept point and a linearity figure-of-merit were measured to be 49.5 dBm and 53.8, respectively.

The interfacial layer formed during the soaking procedure of liquid phase epitaxy (LPE) growth and the heat-up procedure to the growth temperature of metalorganic vapor phase epitaxy (MOVPE) was investigated by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). A thin interfacial layer between an epitaxially grown GaInAsP layer and the concave region of the corrugated InP grating is formed in LPE growth using a GaAs cover crystal. The thickness of this interfacial InAsP layer in the concave region of corrugation is increased with increased AsH 3 partial pressure and heat-up time in MOVPE. The arsenic composition in the InAsP layer also increased with increased AsH 3 partial pressure. Dislocations and defects were not generated in LPE growth using a GaAs cover crystal and using an AsH 3 over pressure and heat-up procedure to the growth temperature in MOVPE.

We have investigated the effect of diethylzinc (DEZn) on the lattice constant and the growth rate of InGaAs. Introducing DEZn for p-type doping induces the contraction of lattice constant and the reduction of growth rate compared to undoped InGaAs. Depletion of indium is responsible for these effects. These effects are reduced at lower growth temperatures or at lower growth pressures. From the observed effects of the growth temperatures and the growth pressures on the contraction of the lattice constant, it is concluded that depletion of indium occurs in the gas phase.

High-speed mesa type SAGCM avalanche photodiodes for 2.5 Gb s-1 optical receivers have been realized for the first time. The device is designed by dimensional analysis based on the electric field distribution in a multiplication layer and a charge plate layer. Very low dark current and high gain are obtained with an active region of 30 μm diameter. From the 1.55 μm wavelength 2.488 Gb s-1 transmission experiment, sensitivity of-33.6 dBm is measured using pseudorandom (223–1) NRZ patterns.

A distributed feedback (DFB) laser module has been developed for 2.5 Gbs-1 optical transmission systems. The DFB laser has a multiple-quantum-well (MQW) active layer and a planar buried heterostructure (PBH) for a low threshold current and stable singlemode operation with low chirping. A PBH DFB laser module with a single-mode fibre pigtail and an optical isolator was designed and fabricated by employing a single lens and a laser welding method. The fabricated MQW PBH DFB laser module is shown to be a suitable light source for 2.5 Gb s-1 optical transmission systems with a minimum received power of-33 dBm after 47 km conventional optical fibre transmission.

For CDMA/AMPS dual-mode cellular phones, a power amplifier operating at 3.3 V has been developed for the first time. It consists of linear GaAs power MESFET's and an output matching circuit which reduces the second and the third harmonics. The amplifier shows an output power of 31.5 dBm and a power-added efficiency of 61% for the AMPS mode. The third-order intermodulation distortion and the fifth-order one are measured to be -32 dBc and -45 dBc at an output power of 26 dBm for the CDMA mode.

Preparation of n-ZnO/p-Si heterostructures using solution-synthesized ZnO nanowire films and their photovoltaic characterization is reported. The solution-grown ZnO nanowire film is characterized using scanning electron microscope, electron dispersive x-ray, and optical absorption studies. Electrical and photovoltaic properties of the fabricated heterostructures are studied using e-beam-evaporated aluminum as metal contacts. In order to use transparent contact and to simultaneously collect the photogenerated carriers, sandwich-type solar cells were fabricated using ZnO nanorod films grown on p-silicon and indium tin oxide (ITO) coated glass as ITO/n-ZnO NR/p-Si. The electrical properties of these structures are analyzed from current-voltage (I−V) characteristics. ZnO nanowire film thickness-dependent photovoltaic properties are also studied. Indium metal was also deposited over the ZnO nanowires and its effects on the photovoltaic response of the devices were studied. The results demonstrated that all the samples exhibit a strong rectifying behavior indicating the diode nature of the devices. The sandwich-type ITO/n-ZnO NR/p-Si solar cells exhibit improved photovoltaic performance over the Al-metal-coated n-ZnO/p-Si structures. The indium deposition is found to show enhancement in photovoltaic behavior with a maximum open-circuit voltage (Voc) of 0.3 V and short-circuit current (Isc) of 70×10−6 A under ultraviolet light excitation.

For low LO power and broadband characteristics of the mixer, an antipodal fin-line to microstrip transition for operation in the 94 GHz frequency has been designed and characterized. Back to back transitions fabricated on soft substrates have been measured and simulated to verify their behavior. A single balanced fin-line mixer was designed and fabricated. In the mixer, a wideband fin-line to coplanar waveguide 180/spl deg/ balun and low pass filter were used. Conversion loss is less than 10 dB at LO power of 6 dBm.

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.3 V has been developed using the low-high doped channel structure. The device has 0.8-/spl mu/m gate length and 21-mm gate width. The power performance tested at a 2.3 V drain bias under 900 MHz operation frequency was output power of 31.3-dBm with 11.3-dB gain and 69-percent power-added efficiency. A third-order intercept point was evaluated to be 50.7-dBm. A Linearity Figure-of-Merit of 55.6 was recorded for 21-mm-wide FET.

A 3.3 v 150 mW IF IC is implemented using 0.8 /spl mu/m CMOS process. This IC integrates both CDMA and FM IF signal processing units and interfaces between IF signals and baseband modem. Rx mixer down-converts 85.38 MHz IF signals into baseband signal, and Tx mixer based on a replica transconductor up-converts baseband signal into a 130.38 MHz IF signal. The chip size is 5.5/spl times/6.3 mm/sup 2/.

We obtained uniform and high coupling efficiency for InGaAsP-InP buried heterostructure (BH) optical amplifiers integrated with butt-coupled waveguides using reactive ion etching (RIE) for mesa definition and low-pressure metalorganic vapor phase epitaxy (LPMOVPE) for waveguide layer regrowth. Measured average coupling efficiency was over 91% across a quarter of 2-in InP wafer. RIE etched vertical facet and a subsequent chemical etching using HBr-based solution for relief of RIE damage enabled us to reduce the coupling loss due to anomalous regrowth shape at the interface. RIE and selective regrowth processes are promising techniques for the fabrication of the photonic integrated circuit (PIC).

A new method to determine intrinsic and extrinsic base-collector capacitances of HBT's using the Miller effect is presented. The measured S-parameters of an HBT are calibrated and transformed into the ABCD-parameters. The fictitious input and output resistances are added to the HBT and total ABCD-parameters are calculated. The added output resistance degrades the frequency response of the overall network due to the Miller effect, which is used to extract intrinsic and extrinsic base-collector capacitances. The advantage of this method is that it does not require any special test structure. >

An InAsP phase formed during the heatup time to the growth temperature of MOVPE was investigated by transmission electron microscopy and energy dispersive spectroscopy. The thickness of the InAsP phase on the concave regions of corrugation is increased with increased AsH3 partial pressure and heat‐up time. The arsenic composition in InAsP was also increased with the increase of AsH3 partial pressure during the heat‐up time. Dislocations and defects were not generated below an AsH3 partial pressure of 2.4×10−3 Torr, although strain was induced according to the thickness and composition of InAsP formed on the concave regions of corrugation.

The fully passivated low noise AlGaAs/InGaAs/GaAs pseudomorphic (PM) HEMT with 0.13 /spl mu/m T-shaped gate was fabricated using dose split electron beam lithography method (DSM). This device exhibited low noise figures of 0.31 and 0.45 dB at 12 and 18 GHz, respectively. These noise figures are the lowest value ever reported for the GaAs based HEMT's. These results are attributed to the extremely low gate resistance which results from wide head T-shaped gate having the higher ratio more than 10 of gate head length to gate footprint.

In this paper, we present a high performance V-band quadruple sub-harmonic mixer monolithic circuit which is designed and fabricated for the millimeter wave down converter applications. While the typical sub-harmonic mixers use a half of fundamental frequency, we adopt a quarter of the fundamental frequency. The proposed circuit is based on sub-harmonic mixer with APDP (anti parallel diode pair). Upon the typical mixer design, additional stubs are placed with the modification of original stub length. And the 0.1 /spl mu/m pseudomorphic high electron mobility transistors (PHEMTs) providing better gain are positioned to each port. Used lumped elements at IF port, it provides selectivity of IF frequency, and increases isolation. Maximum conversion gain of 0.8 dB at a LO frequency of 14.5 GHz and at a RF frequency of 60.4 GHz is measured. Both LO-to-RF and LO-to-IF isolations are higher than 40 dB. These conversion gain results and isolation characteristic are the best performances reported among the quadruple sub-harmonic mixers operating in the V-band millimeter wave frequency thus far.

In this paper, we present V-band high conversion gain quadruple subharmonic mixers adopting the cascode structure. The subharmonic mixers were successfully integrated by using 0.1 /spl mu/m GaAs PHEMTs and the coplanar waveguide structures. We show that the highest conversion gain of 3.4 dB thus far at a LO power of 13 dBm from the fabricated mixers. The millimeter-wave subharmonic mixer also ensure a high degree of isolation showing -53.6 dB in the LO-to-IF and -46.2 dB in the LO-to-RF, respectively, at a frequency of 14.5 GHz. The high conversion gain achieved in this work is the first report among the millimeter-wave monolithic IC subharmonic mixers.

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.9 V has been developed using the high-low doped channel structure grown by molecular beam epitaxy. The device has 0.6 /spl mu/m gate length and 16 mm gate width. The power performance tested at a 2.9 V drain bias and 900 MHz operation frequency was output power of 31.5 dBm with 11.5 dB gain and 64% power-added efficiency. >

A very low operation current (20 mA) has been achieved for the first time with an InGaAsP/InP total-internal-reflection optical switch. The optical switch is fabricated on an n/sup +/-InP substrate using p/n/p/n current blocking layers. This switch has a large effective contact area and is a self-aligned structure. This is a promising result for making optical integrated circuits. >

We obtained uniform and high performance for 1.3 /spl mu/m InGaAsP/InP buried heterostructure (BH) integrated laser with butt-coupled waveguides using reactive ion etching (RTE) for mesa definition and low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) for waveguide and blocking layer regrowth. Measured average coupling efficiency between active layer and passive waveguide layer was over 91% per facet across a quarter of 2-inch InP wafer. The average threshold current and slope efficiency were 13 mA and 0.26 mW/mA of the 700 /spl mu/m long integrated laser, respectively. These uniform and high performance was attributed to the uniform etching characteristics of RIE and a slight chemical etching using HBr-based solution for relief of RIE damage.

Using a low noise active balun and a push-pull active matching circuit, a wideband low noise amplifier MMIC is designed and fabricated. For the frequency up to 3 GHz, output VSWR is less than 1.3 and the output power handling capability of 9.4 dB is enhanced compared with conventional active matching circuit.

A front-end receiver MMIC for 3.3 V-operating CDMA/AMPS dual-mode hand held phone has been developed using a GaAs MESFET process. The developed MMIC, chip size of which is 1.9/spl times/3.9 mm/sup 2/ shows noise figure of 2.8 dB, power gain of 35/25 dB at the nominal current consumption of 22.5/16.1 mA in CDMA/AMPS modes, respectively.

The purpose of this paper is to propose a reliability parameter of laser diodes for optical communication system applications. Based on the alarm function in optical communication systems, we have developed a reliability parameter; /spl rho//sub a/(=/spl eta//sub a///spl eta//sub 0/.Ith/sub a//Ith/sub 0/)/spl ges/1.5, which is more applicable to estimate reliability projections and to design LD modules for optical communication systems.