Reliability of AllnAs/lnGaAs/lnP HEMT with WSi ohmic contacts

We have investigated the degradation mechanism of Al_0.48In_0.52As/In_0.53Ga_0.47As/ InP high electron mobility transistors (HEMTs) using WSi ohmic electrodes. Cross-sectional transmission electron microscopy (TEM) observation and en-ergy dispersive x-ray (EDX) analysis reveal impurities diffusion of gate electrode (titanium: Ti) and fluorine (F) in the AlInAs layer after a high temperature (T_a = 170°C operating life test for 500 h. The decrease of drain current (I_ds) during life test shows linear dependence on square root of aging time. It suggests that the degradation is controlled by a diffusion mechanism. Hence, the estimated degradation mechanism of this device is related with decrease of carrier concentration in the epitaxial layer by these diffused impurities. On the other hand, TEM and EDX show no degradation of WSi/InGaAs interface after aging. Therefore, the WSi electrode for this type of HEMT demonstrates excellent high stability under the accelerated operating life test.     

Optical and electrical properties of Al2O3 films containing silicon nanocrystals

Optical, electrical, and structural properties of Al₂O₃ films subjected to silicon-ion implantation and annealing were investigated by means of photoluminescence measurements, current-voltage measurements and transmission electron microscopy. Transmission electron microscopy revealed that silicon nanocrystals were epitaxially formed in ϑ-Al₂O₃. Visible photolum inescence was observed, for the first time, from Al₂O₃ films containing silicon nanocrystals. Observed visible photoluminescence seems to be related to quantum size effects in silicon nanocrystals as well as localized radiative recombination centers located at the interface between silicon nanocrystals and matrix, similar to porous Si and other Si nanostructures. The conduction mechanism in the samples was studied by using dc current-voltage measurements. The conduction properties depend on temperature and applied electric fields. The conduction behavior in low electric fields consists of thermally activated region dominated by the Schottky conduction and nonthermally activated region in which carrier transport is controlled by space-charge-limited currents. The conduction behavior under relatively high electric fields is almost independent of temperature and well fitted by space-charge-limited conduction.     

FreeWalk: a 3D virtual space for casual meetings

A meeting environment for casual communication in a networked community, FreeWalk provides a 3D common area where everyone can meet and talk freely. FreeWalk represents participants as 3D polygon pyramids, on which their live video is mapped. Voice volume remains proportional to the distance between sender and receiver. For evaluation, we compared communications in FreeWalk to a conventional desktop videoconferencing system and a face-to-face meeting     

Packaging properties of ALIVH-CSP using SBB flip-chip bondingtechnology

A new chip scale package (CSP) using an organic laminated substrate called μCSP was developed, which was fabricated using ALIVH substrate as a interposer and stud-bump-bonding (SBB) flip-chip technology. The ALIVH substrate is a multilayered organic substrate with inner via holes in any layer. The newly developed CSP-L using ALIVH substrate realized a miniaturization of its package size to the same as a CSP using a ceramic substrate (CSP-C). In order to perform the SBB flip-chip bonding onto the ALIVH substrate, an excellent coplanarity of the substrate surface was required. The required coplanarity was obtained using a fixture during the SBB flip-chip bonding process. The first-level packaging reliability and the second-level packaging reliability onto ALIVH mother board were evaluated. The resulting reliabilities were good enough to apply to practical use     

Zn-Al-Mg-Ga alloys as Pb-free solder for die-attaching use

Zn-based alloys have been investigated to replace Pb-5%Sn solder for die-attaching use. We have found that a Zn-4%Al-3%Mg-3%Ga alloy has a 309°C solidus and a 347°C liquidus. A die-attaching test was done with preforms of this alloy, Ag-plated lead-frames, and Au-plated dummy dies. Good die-attaching with a small amount of voids can be achieved at 320°C or higher. In subsequent reliability tests, no failure was observed until 1000 cycles between −65°C and 150°C or until 1000 h at 85°C and 85% humidity. Although the poor workability and poor ability of stress relaxation at room temperature of this alloy may somewhat limit its application areas, this solder is the first Pb-free solder for die-attaching use to our knowledge.     

A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.     

Miscibility gap due to ordering in the BCC Fe-Ge system

Phase equilibria in the bcc Fe-Ge system have been investigated by means of electron probe microanalysis and transmission electron microscopy. Two kinds of ordered phases, B2 and DO₃ types, have been detected, the B2 phase being formed from the disordered A2 phase by a 2nd order transition. The DO₃ phase is also formed from the B2 phase by a 2nd or higher order transition at higher temperatures. Below about 820 °C, however, the transition becomes a 1st order, and a miscibility gap between these ordered phases occurs in the composition range from 13 to 16 at. pct Ge. It has been also confirmed that the solubility of Ge in the bec phase shows a retrogression due to the formation of DO₃ phase. On the basis of these experimental results, the phase diagram for the Fe-Ge system has been partly revised.     

Detection of antibodies to Borrelia species among patients with confirmed sarcoidosis in a region where Lyme disease is nonendemic

BACKGROUND: Lyme disease is a multisystemic disorder caused by the spirochete Borrelia burgdorferi, while sarcoidosis is a multisystemic granulomatous disease of unknown etiology. The purpose of this study was to evaluate the relationship between Lyme disease and sarcoidosis. METHODS: We examined the seroprevalence of antibody to Borellia species in patients with sarcoidosis. We performed the enzyme-linked immunosorbent assay, using three Japanese Borrelia species in addition to B. burgdorferi, and dotblot analysis using purified Borrelia-specific proteins in 38 patients with histopathologically confirmed sarcoidosis and 80 healthy controls. RESULTS: Two patients (5.3%) were positive for antibodies to Borrelia species according to one or both assays, and one (1.2%) healthy control was positive. In both patients it was suspected that Borrelia infection had developed prior to the development of sarcoidosis. CONCLUSION: Borrelia species were thought not to be responsible for the development of sarcoidosis in a nonendemic region in Japan. Since clinical manifestations of Lyme disease share certain similarities with those seen in sarcoidosis, ophthalmologists should be aware of the need to differentiate between the two diseases and the need for prompt treatment in each case.     

CD7 positive acute lymphoblastic leukemia successfully treated with high dose cytosine arabinoside and mitoxantrone: a case report

Primary Sjogren's syndrome (pSS) is a common autoimmune connective tissue disease in China yet without a universally accepted diagnostic criteria. In this study a new criteria was proposed and compared with other six sets of criteria. Fifty-five items in 112 pSS and 185 controls were evaluated. Results show the criteria we proposed contained one major and nine minor items. For the purpose of identifying patients in clinical studies, a major with at least three of the nine minor items or at least five of the minor items should be presented. The major item is anti-SSA/SSB(+) and the minors are, (1) dry eyes or dry mouth (> 3 months, persistently), (2) swollen salivary glands (recurrently or persistently), (3) rampant dental caries, (4) Schirmer test (< 5 mm in 5 min.) or corneal staining(+), (5) unstimulated salivary flow (< 0.03 ml/min) or abornal parotid sialography, (6) minor salivary gland biopsy (> or = 1 focus), (7) renal tubular acidosis, (8) hypergammaglobuminemia (gamma globulin > or = 30%) or hypergammaglobuminemic purpura, (9) RF > 1 : 20 or ANA > 1 : 20. Other connective tissure diseases, pre-existing lymphoma, AIDS, sarcoidosis, graft vs host disease must be excluded. The criteria we proposed had a high specificity of 98.2% and sensitivity of 94.1%.