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GaAs based heterojunction bipolar transistors have a relatively large turn-on voltage of approximately 1.4 V that can only be decreased by reducing the bandgap energy of the base material. For a variety of applications, particularly operation with low power supply voltage and reduced power dissipation, it would be desirable to have a smaller value of turn-on voltage. We report the DC performance of NpN double heterojunction bipolar transistors fabricated on a GaAs substrate with a Ga 0.89 In 0.11 N 0.02 As 0.98 -base that has a bandgap energy ( E g ) of ∼0.98 eV. These devices have a turn-on voltage V BE that is 0.4 V lower than that of their GaAs-base counterparts. To overcome the large conduction band discontinuity between GaAs and Ga 0.89 In 0.11 N 0.02 As 0.98 both chirped superlattice and delta doping were employed. Peak incremental current gain of h fe =8.5 was obtained.

Two kinds of defective growth in 4H-SiC trench filling were found to be associated with the compositional ratio of supplied gases. An input HCl/SiH4 ratio below 35 leads to overgrowth around the mesa, forming voids. Overetching on the mesa induces an etched mesa when HCl is supplied in excess, e.g., HCl/SiH4 > 65 (SiH4 = 30 sccm). Thus, an empirical window for nondefective growth is discerned. It also contains a high-filling-rate area around HCl/SiH4 ~50, which proves well-proportioned etching and deposition reactions, and 25-µm-deep trenches (aspect ratio of ~11) are successfully filled at a rate as high as 4.3 µm/h.

Idiopathic hyperammonemia (IHA) has been described as a complication of intensive chemotherapy for the treatment of hematologic malignancy but has subsequently been found in patients undergoing bone marrow transplantation and in those with solid tumors treated with 5-fluorouracil. Although IHA is a rare complication, it is sometimes associated with high mortality in hematologic malignancies. Here we report the case of a 15-year-old boy in whom hyperammonemia developed during the initial treatment with prednisolone for newly diagnosed acute lymphoblastic leukemia and who survived after early detection and oral lactulose therapy. To the best of our knowledge, this is the first report of IHA that was not induced by intensive chemotherapy, stem cell transplantation, or asparaginase therapy in a patient with newly diagnosed leukemia, but developed during an initial treatment with a steroid. Early detection of IHA by measuring the plasma ammonia level in patients with neurological symptoms may improve the outcome.

Small-scale InGaP/GaAs heterojunction bipolar transistors (HBTs) with high-speed as well as low-current operation are demonstrated. To reduce the emitter size SE and the base-collector capacitance CBC simultaneously, the HBTs are fabricated by using WSi/Ti as the base electrode and by burying SiO 2 in the extrinsic collector region. WSi/Ti metals simplify and facilitate processing to fabricate small base electrodes, and the buried SiO 2 reduces the parasitic CBC under the base electrode. The cutoff frequency fT of 156 GHz and the maximum oscillation frequency f max of 255 GHz were obtained at a collector current Ic of 3.5 mA for the HBT with SE of 0.5 μ m ×4.5 μ m , and fT of 114 GHz and f max of 230 GHz were obtained at IC of 0.9 mA for the HBT with SE of 0.25 μ m ×1.5 μ m . A 1/8 static frequency divider operated at a maximum toggle frequency of 39.5 GHz with a power consumption per flip-flop of 190 mW. A transimpedance amplifier provides a gain of 46.5 dB·Ω with a bandwidth of 41.6 GHz at a power consumption of 150 mW. These results indicate the great potential of our HBTs for high-speed. low power integrated circuit applications.

We have developed the advanced performance, small-scale InGaP/GaAs heterojunction bipolar transistors (HBTs) by using WSi/Ti base electrode and buried SiO/sub 2/ in the extrinsic collector. The base-collector capacitance C/sub BC/ was further reduced to improve high-frequency performance. Improving the uniformity of the buried SiO/sub 2/, reducing the area of the base electrode, and optimizing the width of the base-contact enabled us to reduce the parasitic capacitance in the buried SiO/sub 2/ region by 50% compared to our previous devices. The cutoff frequency f/sub T/ of 156 GHz and the maximum oscillation frequency f/sub max/ of 255 GHz were obtained at a collector current I/sub C/ of 3.5 mA for the HBT with an emitter size S/sub E/ of 0.5/spl times/4.5 /spl mu/m/sup 2/, and f/sub T/ of 114 GHz and f/sub max/ of 230 GHz were obtained at I/sub C/ of 0.9 mA for the HBT with S/sub E/ of 0.25/spl times/1.5 /spl mu/m/sup 2/. We have also fabricated digital and analog circuits using these HBTs. A 1/8 static frequency divider operated at a maximum toggle frequency of 39.5 GHz with a power consumption per flip-flop of 190 mW. A transimpedance amplifier provides a gain of 46.5 dB/spl middot//spl Omega/ with a bandwidth of 41.6 GHz at a power consumption of 150 mW. These results indicate the great potential of our HBTs for high-speed, low-power circuit applications.

This paper describes a novel heterojunction bipolar transistor (HBT) structure, the collector-up tunneling-collector HBT (C-up TC-HBT), that minimizes the offset voltage V/sub CE,sat/ and the knee voltage V/sub k/. In this device, a thin GaInP layer is used as a tunnel barrier at the base-collector (BC) junction to suppress hole injection into the collector, which results in small V/sub CE,sat/. Collector-up configuration is used because of the observed asymmetry of the band discontinuity between GaInP and GaAs depending on growth direction. To minimize V/sub k/, we optimized the epitaxial layer structure as well as the conditions of ion implantation into the extrinsic emitter and post-implantation annealing. The best results were obtained when a 5-nm-thick 5/spl times/10/sup 17/-cm/sup -3/-doped GaInP tunnel barrier with a 20-nm-thick undoped GaAs spacer was used at the BC junction, and when 2/spl times/10/sup 12/-cm/sup -2/ 50-keV B implantation was employed followed by 10-min annealing at 390/spl deg/C. Fabricated 40/spl times/40-/spl mu/m/sup 2/ C-up TC-HBTs showed almost zero V/sub CE,sat/ (

This paper describes a new approach to fabricating InGaP/GaAs heterojunction bipolar transistors (HBT's) with a high cutoff frequency (f/sub T/), high maximum oscillation frequency (f/sub max/), and low external collector capacitance (C/sub bc/). To attain a high f/sub T/ and f/sub max/, a heavy carbon-doping (1.3/spl times/10/sup 20/ cm/sup -3/) technique was used with a thin (30-nm-thick) GaAs base layer, while for low C/sub bc/, low-temperature gas-source molecular-beam epitaxial growth on SiO/sub 2/-patterned substrates was used to bury high-resistance polycrystalline GaAs under the base electrode. An f/sub T/ of 120 GHz and an f/sub max/ of 230 GHz were achieved for three parallel 0.7/spl times/8.5 /spl mu/m HBT's with an undoped-collector structure, and an f/sub T/ of 170 GHz and an f/sub max/ of 160 GHz were obtained for a single 0.9/spl times/10 /spl mu/m HBT with a ballistic-collection-transistor structure. Compared to HBT's without buried poly-GaAs, the maximum stable gain was improved by 1.2 dB in the 0.7/spl times/8.5 /spl mu/m HBT and by 2.3 dB in the 0.9/spl times/10 /spl mu/m HBT due to the reduction in C/sub bc/. These results show the high potential of the proposed HBT's for high-speed digital and broadband-amplifier applications.

This paper describes the fabrication and characteristics of small-scaled InGaP/GaAs HBTs with high-speed as well as low-current operation. To reduce both the emitter size S/sub E/ and the base-collector capacitance C/sub BC/ simultaneously, the HBTs are fabricated by using WSi/Ti as the base electrode and by burying SiO/sub 2/ in the extrinsic base-collector region under the base electrode. WSi/Ti simplifies and facilitates processing to fabricate a small base electrode, and makes it possible to reduce the width of the base contact to less than 0.4 /spl mu/m without the large increase in the base resistance. The DC current gain of 20 is obtained for an HBT with S/sub E/ of 0.3/spl times/1.6 /spl mu/m/sup 2/ due to the suppression of emitter size effect by using InGaP as the emitter material. An HBT with SE of 0.6/spl times/4.6 /spl mu/m/sup 2/ exhibited f/sub T/ of 138 GHz and f/sub max/ of 275 GHz at I/sub C/ of 4 mA; and an HBT with SE of 0.3/spl times/1.6 /spl mu/m/sup 2/ exhibited f/sub T/ of 96 GHz and f/sub max/ of 197 GHz at I/sub C/ of 1 mA. These results indicate the great potential of these HBTs for high-speed and low-power circuit applications.

InGaP/GaAs heterojunction bipolar transistors (HBTs) with a heavily-doped and thin base layer are described. Low base leakage current of 2.3 × 10 −7 A μm −1 at the emitter-base periphery was obtained, and excellent high-frequency performances of a cut-off frequency f T of 115 GHz and a maximum oscillation frequency f max of 159 GHz were achieved by using a 30 nm-thick base layer doped to 1 × 10 20 cm −3 , which is the first report of both parameters being over 100 GHz in an InGaP/GaAs HBT. Delay time component analysis exhibited that the intrinsic transit time was reduced by 0.4 ps by reducing the base thickness from 50 to 30 nm.

Posttranscriptional modification of histones by methylation plays an important role in regulating Ag-driven T-cell responses. We have recently drawn correlations between allogeneic T-cell responses and the histone methyltransferase Ezh2, which catalyzes histone H3 lysine 27 trimethylation. The functional relevance of Ezh2 in T-cell alloimmunity remains unclear. Here, we identify a central role of Ezh2 in regulating allogeneic T-cell proliferation, differentiation, and function. Conditional loss of Ezh2 in donor T cells inhibited graft-versus-host disease (GVHD) in mice after allogeneic bone marrow (BM) transplantation. Although Ezh2-deficient T cells were initially activated to proliferate upon alloantigenic priming, their ability to undergo continual proliferation and expansion was defective during late stages of GVHD induction. This effect of Ezh2 ablation was largely independent of the proapoptotic molecule Bim. Unexpectedly, as a gene silencer, Ezh2 was required to promote the expression of transcription factors Tbx21 and Stat4. Loss of Ezh2 in T cells specifically impaired their differentiation into interferon (IFN)-γ–producing effector cells. However, Ezh2 ablation retained antileukemia activity in alloreactive T cells, leading to improved overall survival of the recipients. Our findings justify investigation of modulating Ezh2 as a therapeutic strategy for the treatment of GVHD and other T cell–mediated inflammatory disorders.

Myeloid/natural killer cell precursor acute leukemia (MNKL) is an aggressive disease with a high relapse rate even after allogeneic hematopoietic stem cell transplantation (SCT). We report a patient with MNKL who had a donor lymphocyte infusion (DLI) for relapse after T cell-replete human leukocyte antigen (HLA)-haploidentical SCT, but relapsed again 20 months later with loss of mismatched HLA. This case suggests that a strong graft-versus-leukemia effect of haploidentical SCT can be expected in MNKL patients. In the haploidentical setting, DLI should be considered for patients with relapsed leukemia whose leukemic cells have not lost HLA cell surface expression.

The effect of the nitrogen concentration on the properties of ZnTe-based contact structures consisting of a p-ZnTe layer, a ZnSe ZnTe graded superlattice (SL), and a p-ZnSe layer is described. The degree of nitrogen-doping into the ZnSe ZnTe SL and into the ZnTe layer was changed by modulation doping. The ohmic I-V characteristics were observed in samples with an N-doped ZnSe undoped ZnTe SL and in samples with a ZnTe layer with a nitrogen concentration of 3 × 1018cm−3. When the nitrogen concentration in the ZnSe ZnTe SL region or the ZnTe layer was increased, nitrogen diffusion into the ZnSe layer was observed by SIMS and PL measurement. The ZnSe layer then became highly resistive, probably because deep donors were induced by the nitrogen diffusion.

A trench filling epitaxial growth technique using hot-wall chemical vapor deposition with HCl gas has been developed for SiC super-junction (SJ) device fabrication. 2–6 kV class SJ devices require p/n column structures with depths of over 10 µm. However, rapid trench closure before the trench backfilling process is complete makes these structures difficult to realize. Stripe trenches that were intentionally inclined within ±2° on a surface plane towards the direction were formed on an off-angled wafer, and the effects of trench direction misalignment from the off-direction were investigated. Slight trench direction misalignment was found to affect the tilt angle of the mesa top epi-layer strongly. Tilted growth on the mesa top reduced the filling rate at the trench bottom and caused void formation. When a wafer with high orientation-flat accuracy relative to the direction was used, 25-µm-deep trench backfilling was successfully demonstrated.

[Introduction] EBV-PTLD is a serious complication in hematopoietic stem cell transplantation (HSCT) recipients. We conducted a retrospective study to investigate the incidence and potential risk factors for EBV reactivation and to assess the efficacy of the management of EBV reactivation with preemptive rituximab in children who had T-cell-replete haploidentical HSCT (TCR-haplo-SCT) with low-dose anti-thymocyte globulin (ATG). [Methods] A total of 38 patients who underwent haplo-SCT in a single institution (Fukushima Medical University Hospital, Fukushima, Japan) between October 2009 and December 2014 were included in this retrospective study. Those patients were tested for EBV-DNA levels in PB at least once after HSCT when they showed suspicious symptoms of EBV reactivation. During this study period, haplo-SCT with low-dose ATG was performed on those patients with high-risk childhood acute leukemia or solid tumor with the expectation of a strong GVL/GVT effect. On the other hand, a patient with immunodeficiency syndrome underwent haplo-SCT because of the lack of an HLA-matched related or unrelated donor. When the EBV-DNA level in PB increased to >1,000 copies/106 peripheral blood mononuclear cells (PBMCs), patients were preemptively treated with rituximab (375 mg/m2/dose). For patients with a decrease in EBV viremia titer following one dose of rituximab, viral loads were monitored weekly to follow their response to rituximab. For patients with persistent viremia, an additional weekly dose of rituximab was administered until the resolution of the viremia. Whenever possible, immunosuppressants were tapered. [Results] All HSCTs were T-cell-replete, and all patients received ATG at a dose of 2.5 mg/kg during conditioning. Thirty-eight patients were included in this study with a median follow up of 625 (range, 59-2084) days post-transplantation. Among them, 32 (84%) patients became EBV-DNA-positive, with 19 of 38 (50% of the total population) patients presenting with EBV reactivation and requiring preemptive treatment. In detail, 13 patients with transient, self-limiting EBV-DNA positivity had a mean peak level of 140 cp/106 PBMCs (range: 17-880), while the 19 patients who presented with EBV reactivation showed a mean EBV-DNA level of 2900 cp/106 PBMCs (range: 1000-650000). The median time from transplantation to EBV reactivation was 56 (range, 17-270) days and the median viral load at initiation of therapy was 2900 cp/106 PBMCs (range: 1000-650000). Preemptive therapy was started after a median of 2 (range, 0-7) days of qPCR result. The median number of weekly treatment cycles was 2 (range, 1-3). Fever was noted after rituximab infusion in one of the 19 patients, although no other side effects were observed. Seventeen of those 19 (89%) patients sustained viral loads of [Conclusion] We conclude that preemptive rituximab therapy is effective for EBV-PTLD in TCR-haplo-SCT recipients with low-dose ATG. Disclosures No relevant conflicts of interest to declare.

Background: T-cell rich (TCR) HLA-haploidentical SCT (haplo-SCT) is a form of T-cell therapy that has a high degree of efficacy in hematologic malignancies. Previously we reported the safety profile assessing GVHD prophylaxis that was conducted with anti-human thymocyte immunoglobulin (ATG), tacrolimus, methotrexate (MTX) and prednisolone (PSL) in unmanipulated haplo-SCT (Clin Transplant 2010, Transfus Med 2014). We evaluated efficacy and toxicity of TCR haplo-SCT in children with very high risk refractory/relapsed acute leukemia (VHR-R/R AL). Methods: VHR-R/R AL were defined as: relapse after SCT, very early or early relapse, induction failure(2 or more) and relapse of risk factor with MLL rearrangement, Ph+, Mo7 and 5q-. From Aug 2000 to April 2014, consecutive 38 patients (pts) with VHR-R/R AL who underwent TCR-haplo-SCT were included. The median age of pts was 8.2(0.3-19.1) years old. The diagnosis included ALL (n=27), AML (n=8), M/NKL (n=3). The disease status at TCR-haplo-SCT were 18 in CR (positive MRD: 8 pts), 20 in non-CR. HLA disparities were 2/8 in 1pt, 3/8 in 9 pts, 4/8 in 28 pts. Donors included fathers (n=21), mothers (n=14), and siblings (n=3). Thirty one pts received myeloablative conditioning (TBI based: 20 pts, Bu based: 11 pts) and 34 pts of them received ATG (rabbit, thymoglobulin 2.5mg/kg) containing regimen. The GVHD prophylaxis was conducted with tacrolimus, MTX and PSL. Thirty four pts received peripheral blood stem cells and 4 pts received BM. Results: Neutrophil engraftment (defined as >0.5x109/L) was 95% with a median day of 13 (range, 10-15). With a median 1640 days follow-up (range, 320-5510 days) in pts without events, the actuarial 3-year overall survival (OS) and disease-free survival (DFS) were 57% and 39%, respectively. On competing-risk analysis, 1-year cumulative incidences of grade II-IV acute GVHD and chronic GVHD were 71% and 63%, respectively; 3-year cumulative incidences of relapse and non-relapse mortality (NRM) were 40% and 20%. On univariate analysis, 3-year OS in pts with acute GVHD vs. without acute GVHD were 70% vs. 22% (p=.0006), in pts CR vs. non-CR at TCR-SCT were 83% vs. 32% (p=.007), in pts infused CD3 cell doses >=5 x 108/kg vs. =9 were 79% vs. 34% (.008), respectively. In contrast, the occurrence of acute GVHD had no significant difference in infused CD3 cell doses. Conclusions: These data suggest that TCR haplo-SCT following low-dose ATG containing conditioning combined with our GVHD prophylaxis is well tolerated, facilitates engraftment, and has significant anti-leukemic activity, particularly in pediatric patients with refractory/ relapsed population. Disclosures No relevant conflicts of interest to declare.

The crystallographic microstructure and electrical characteristics of Au/Pt/Ti/Ni ohmic contacts on p‐type (001) ZnTe layers are investigated as a function of annealing temperature, by using the transmission line model method, cross‐sectional transmission electron microscopy, and Auger electron spectroscopy. The specific contact resistance decreases when the annealing temperature is increased and reaches a minimum at 300 °C. A minimum value of 1.1×10−6 Ω cm2 is obtained for a hole concentration of 3×1019 cm−3. The epitaxial NiTe2 that formed at the metal/semiconductor interface due to annealing is considered to play an important role in lowering the contact resistance. The excess Zn atoms created by the reaction between Ni and ZnTe are found to diffuse upward and to segregate at the Pt/Ni interface. A contact stability test performed at 102 °C suggests that these ohmic contact structures are stable even under high‐current injection.

To improve the performance of GaN power devices, we have investigated the crystalline quality of thick (>20 µm) carbon-doped GaN layers on n-type GaN substrates and templates. The surface morphologies and X-ray rocking curves of carbon-doped GaN layers were improved by using GaN substrates. However, the crystalline quality degraded when the carbon concentration was too high (1 × 1020 cm−3), even in the case of GaN substrates. High breakdown voltages (approximately 7 kV under a lateral configuration) were obtained for the carbon-doped GaN layers on n-type GaN substrates when the carbon concentration was 5 × 1019 cm−3. These results indicate that lateral power devices with high breakdown voltage can be fabricated by using thick carbon-doped GaN buffer layers, even on n-type GaN substrates.

A decrease in breakdown voltage (VBD) in the termination area of 4H-SiC PN diodes after 64 h reverse-bias stressing was analyzed. To analyze the VBD decrease, a novel analysis method based on the results of measuring depletion-layer capacitance of the PN diodes was proposed. The measurement results indicate that the positive-charge density (QTM) at the SiO2/SiC interface of the termination area increased after the reverse-bias stressing. Besides, in the case of QTM of 1012 cm−2 at the SiO2/SiC interface, the decrease in the measured capacitance showed the same tendency as the decrease in the simulated capacitance. By comparing the measured full depletion voltage and simulated full depletion voltage, the amount of QTM was estimated. It is thus concluded that the proposed method for measuring the depletion-layer capacitance is effective for analyzing the QTM change in the termination area.

The distribution of positive-charge density at the SiO2/SiC interface of the termination area (Q TM) was analyzed by measuring the depletion-layer capacitance of 4H-SiC PN diodes with different termination structures. A change in Q TM induced by reverse-bias stressing (ΔQ TM) caused a change in the breakdown voltage of the diodes. By comparing the measured depletion-layer capacitance to the simulated value, the initial Q TM ( ) and the distribution of ΔQ TM were clarified. It is concluded from these results that the distribution of ΔQ TM was not uniform but that positive charges mostly accumulated in the termination area under a high applied electric field.

The objective of this study was to evaluate the efficacy and safety of our combination therapy in febrile neutropenic children with cancer.A total of 109 patients with 251 episodes of febrile neutropenia received antibiotic therapy between January 2003 and December 2008 at a single institution.Blood cultures were positive in 35 episodes (14%). Gram-positive organisms predominated (23/38 organisms isolated). There were 15 gram-negative isolates and no fungal isolates. The recommended empirical first-line antibiotics (cefepime or cefozopran + piperacillin + amikacin) were used in 206 (82%), second-line antibiotics (piperacillin-tazobactam + carbapenem + amikacin + micafungin) in 73 (29%), and third-line antibiotics (meropenem + glycopeptides + micafungin) in 24 (10%) episodes. The overall response rates were 71.4%, 50.7%, and 62.5% for the first-, second-, and third-line antibiotic therapies, respectively. Granulocyte transfusion was performed in seven patients, and the response rate was 57%. Four deaths were recorded.Although a significant improvement of mortality was not observed, our regimen of empirical antibiotic therapies led to a significant and clinically relevant decrease in glycopeptide use, and it is safe and well tolerated by pediatric neutropenic patients.

Granulocytes were collected by the bag separation method and stored in whole blood for up to 72 h. We evaluated the expressions of various surface antigens: CD62L, CD11b, CD18, CD64, CD16b, and CD95. Apoptosis was assessed both by flow cytometry and by light microscopy. Expression levels of all the surface antigens were shown to be maintained during storage for up to 72 h. Approximately 80% of granulocytes were annexin V negative until 72 h after collection. The storage of granulocyte concentrates collected by the bag separation method may maintain granulocyte surface antigens and lack an apoptotic marker.

Context.—An increasing number of medical centers can collect bone marrow, peripheral blood, or umbilical cord stem cells. Pathology laboratories should accommodate this trend, but investment in additional equipment may be impractical. Objectives.—To compare CD34+ cell counting results by using 2 widely available flow cytometry systems, with and without the use of a separate hematology analyzer (ie, single-platform versus dual-platform methodologies). Design.—Whole blood and peripheral blood stem cell (PBSC) samples were analyzed from 13 healthy allogeneic PBSC donors and 46 autologous PBSC donors with various malignancies. The Cytomics FC500 (Beckman Coulter, Fullerton, California) was compared with the FACSCalibur (BD Biosciences, San Jose, California). Dual-platform CD34+ cell counting incorporated data from a KX-21 hematology analyzer (Sysmex, Kobe, Japan). Results.—Subtle differences in CD34+ cell counting between 2 systems and 2 methods did not achieve statistical significance. Conclusion.—Different systems and methods for CD34+ cell enumeration, properly validated, can support care for patients undergoing transplants and provide meaningful data for multicenter studies or meta-analyses.

To elucidate the correlation between regulatory T cells (Tregs) and acute graft-versus-host disease (aGVHD) or cytomegalovirus infection following allogeneic bone marrow transplantation (allo-BMT), we evaluated either CD4+CD25high or FOXP3+ Treg-enriched cells in peripheral blood (PB) from 20 patients who received allo-BMT, and in biopsies of skin with aGVHD. Proportions of CD4+CD25highFOXP3+ cells in total lymphocytes, but not other types of T cells, were lower in patients who eventually developed grades II–IV aGVHD (n = 13) than in others (n = 7, P

Silicon carbide with a poly-type 4H structure (4H-SiC) is an attractive material for power devices. While bipolar devices mainly utilize 4H-SiC p-n junctions, unipolar devices use p-n junctions both within the active region (to control the electric field distribution) and at the edges of the devices (to reduce electric-field crowding) (Baliga, 2005). In a p-type region, very high doping is necessary since common acceptors have deep energy levels (B: 0.3 eV; Al: 0.2 eV) (Heera et al., 2001). Boron is known to exhibit complex diffusion behaviour (Linnarsson et al., 2003), while aluminum has extremely low diffusivity (Heera et al., 2001). Precise modeling of boron diffusion and aluminum-ion implantation is therefore crucial for developing high-performance 4H-SiC power devices. For carbon-doped silicon, a boron diffusion model has been proposed (Cho et al., 2007). Unfortunately, the results cannot be directly applied to boron diffusion in SiC because of the existence of silicon and carbon sublattices. In addition, knowledge of boron segregation in 4H-SiC is lacking, preventing improvement of such novel devices as boron-doped polycrystalline silicon (poly-Si)/nitrogen-doped 4H-SiC heterojunction diodes (Hoshi et al., 2007). Dopant segregation in elementary-semiconductor/compound-semiconductor heterostructures—in which point defects in an elementary semiconductor undergo a configuration change when they enter a compound semiconductor—has yet to be studied. A framework for such analysis needs to be provided. With regards to aluminum distribution, to precisely design p-n junctions in 4H-SiC power devices, as-implanted profiles have to be accurately determined. For that purpose, Monte Carlo simulation using binary collision approximation (BCA) was investigated (Chakarov and Temkin, 2006). However, according to a multiday BCA simulation using a large number of ion trajectories, values of the simulated aluminum concentration do not monotonically decrease when the aluminum concentration becomes comparable to an n-type drift-layerdoping level (in the order of 1015 cm-3). A continuous-function approximation, just like the dual-Pearson approach established for ion implantation into silicon (Tasch et al., 1989), is thus needed. The historic development and basic concepts of boron diffusion in SiC are reviewed as follows. It took 16 years for the vacancy model (Mokhov et al., 1984) to be refuted by the 2

In this study, we evaluated the feasibility of our graft-versus-host disease (GVHD) prophylaxis with tacrolimus, methotrexate, and prednisolone in non-T-cell-depleted haploidentical hematopoietic stem cell transplantation (HSCT) for children. Twenty-one consecutive patients including those with hematological malignancies (n = 11), solid tumors (n = 7), and non-malignancies (n = 3) were analyzed. Myeloablative and reduced intensity conditionings were carried out in 5 and 16 patients, respectively, and both of the regimens contained anti-human T-lymphocyte immunoglobulin. Twenty (95%) of the 21 patients achieved primary engraftment. Acute GVHD of grades II-IV and III-IV were observed in nine (47%) and one (5%) patient, respectively, all of which were controllable by steroids. Chronic GVHD was observed in eight (51%) of the 17 evaluable patients, and one of them developed steroid refractory chronic GVHD. Treatment-related mortality occurred in three patients (15%), as a result of acute pancreatitis, chronic GVHD, and EB virus associated lymphoproliferative disease. The median follow-up of the 13 survivors was 24 months, and the two-yr probability of overall survival was 68%. The Karnofsky performance scale score of the 13 survivors was 100%. These results indicated the feasibility of our GVHD prophylaxis in non-T-cell-depleted haploidentical HSCT for children.

CGD is a rare inherited immunodeficiency disorder that is caused by disability of oxidative killing. We presented a two-yr-old boy with CGD who was suffering from multiple systemic abscesses. He received the first BMT from his HLA-haploidentical mother after conditioning with Flu, melphalan, and ATG. Although the maximum of 42% donor chimerism was achieved, it disappeared 73 days after the BMT. Then, we performed 5/6-matched unrelated cord blood re-transplantation after conditioning with Flu, Bu, and TBI (2 Gy). Engraftment and complete donor chimerism were achieved on days 18 and 19, respectively. The patient is now free from infection and maintains complete donor chimerism without GVHD 36 months after the cord blood re-transplantation. We postulate that the unrelated CBT has a potential to be an alternative strategy and might be beneficial for patients with CGD who do not have an HLA-identical donor.

A steady-state two-dimensional diffusion equation was numerically analyzed to examine the rate of homoepitaxial growth on a trenched 4H-SiC substrate. The radii of curvature at the top and bottom of the trenches were used to take the Gibbs–Thomson effect into account in the analysis based on the conventional boundary-layer model. When the trench pitch was less than or equal to 6.0 µm, the measured dependence of the growth rate on the trench pitch was found to be explained by the Gibbs–Thomson effect on the vapor-phase diffusion of growing species.

Dendritic cells (DCs) are important for primary T cell responses, and cytokines produced by DCs are thought to be essential for promoting T helper (Th)1 and Th17 differentiation. However, DCs can drive effector differentiation independent of cytokines. In mouse models of graft-versus-host-disease (GVHD), which is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT), we found that DC-derived Notch ligand Dll4 was important for CD4+ Th1 and Th17 cell differentiation. Blocking Dll4 led to decreased production of IFN-g and IL-17 in mice receiving allo-HSCT and inhibition of GVHD. However, the human counterparts of murine DLL4+ DCs and their function in alloreactive T cells have never been investigated. We report here the identification of human DLL4+ DCs and the critical role of DLL4 in DC-regulation of Th1 and Th17 cell differentiation. Flow cytometric analysis revealed that CD1c+ DCs and plasmacytoid DCs (pDCs) from the peripheral blood (PB) of healthy donors (n=18) did not express DLL4. However, 24 hours after stimulation with Toll-like receptor (TLR) agonists, PB DCs from healthy donors produced high levels of DLL4 on their surface. Pam3 (TLR1/2 stimulus), Poly I:C (TLR3 stimulus), LPS (TLR4 stimulus) and R848 (TLR7/8 stimulus) induced high levels of DLL4 expression on the surface of 50% to 80% of CD1c+ DCs. CpG oligodeoxynucleotides (TLR9 agonists) did not increase DLL4 in CD1c+ DCs, likely due to their lacking of TLR9. pDCs increased DLL4 expression when activated by R848 (16.0% ± 2.7%) and to a less extent by CpG oligodeoxynucleotides (8.6% ± 0.8%). Thus, activation of TLR signaling induces high levels of DLL4 in CD1c+ DCs and pDCs, with R848 being the most potent stimulus. Functional analysis using mixed lymphocyte reaction revealed that R848-activated CD1c+ DCs and pDCs induced greater proliferation of allogeneic CD4+ T cells and production of more IFN-g- and IL-17-producing effector cells compared to unstimulated CD1c+ DCs and pDCs. Blocking DLL4 using a neutralizing antibody decreased Notch signaling in T cells stimulated with activated DCs and led to production of 2- and 3-fold less Th1 cells and Th17 cells compared to IgG control, suggesting the importance of DLL4 in DC-regulation of effector differentiation. Molecular mechanism investigation revealed that SATAT3 and NFkB were crucial for inducing DLL4 in human DCs. Inhibiting STAT3 alone using its specific inhibitor S31-201 dramatically decreased DLL4 expression in activated PB DCs. Promoter reporter assays showed that STAT3 was required for activating DLL4 transcription. Inhibiting NFkB using its inhibitor PDTC also decreased the expression of DLL4 on the surface of R848-stimulated PB DCs. However, DCs derived from monocytes induced by GM-CSF and IL-4, which had activation of NFkB but did not express active STAT3 following stimulation by R848 + LPS, were DLL4 negative despite their upregulation of costimulatory molecules (e.g., CD40, CD80, CD83, and CD86). Thus, activation of STAT3 is critical for inducing DLL4 in human DCs, whereas active NFkB is important but not sufficient for inducing DLL4 in PB DCs. Finally, given the importance of alloreactive Th1 and Th17 cells in mediating GVHD in human allogeneic HSCT recipients, we further obtained PB from patients (n=7) undergoing allo-HSCT between 21 and 39 days after transplantation when these patients were fully engrafted and no longer pancytopenic. As compared to healthy donors, HSCT recipients had an averaged 12-fold higher frequency of DLL4+ CD1c+ DCs. These results indicate that upregulation of DLL4 on the surface of DCs is associated with alloreactive inflammatory conditions in HSCT patients. In summary, our findings show that DLL4 surface expression on human DCs is critical for the priming of human Th1 and Th17 responses and may have significant implication in better understanding of T cell-mediated inflammatory conditions such as chronic infection, autoimmune diseases, tumor rejection and GVHD after allo-HSCT. Disclosures No relevant conflicts of interest to declare.

We investigated the achievability of low specific on-resistance and high breakdown voltage by GaN diodes consisting of three, five, and eight two-dimensional-electron-gas (2DEG) channels. The anode Schottky electrode and cathode Ohmic electrode were formed on each side wall of the multi-2DEG-channel and the n-type region was formed by Si-ion implantation in the cathode electrode-formation area of each multi-2DEG-channel. With increasing number of 2DEG channels of the diodes, specific on-resistance (RonA) showed a tendency to decrease; RonA of eight-2DEG-channel diodes was as low as 12.1 mΩ cm2. The breakdown voltage of all the fabricated diodes exceeded 3 kV. Although the electrical characteristics of the multi-2DEG-channel diodes fabricated on sapphire substrates were demonstrated, the number of cracks appearing on the epitaxial layer surface was found to increase with increasing number of 2DEG channels. Such crack formation was concluded to govern the practical limit for the number of 2DEG channels.

InGaP/GaAs heterojunction bipolar transistors (HBTs) with polycrystalline GaAs buried under the base electrode have been fabricated using low-temperature gas-source molecular beam epitaxy on SiO/sub 2/-patterned substrates. A cutoff frequency of 120 GHz and a maximum oscillation frequency of 230 GHz were obtained for three parallel 0.7/spl times/8.5 /spl mu/m HBTs. Compared to HBTs without the polycrystal, the collector capacitance was reduced by 28% and the maximum stable gain was improved by 1.2 dB due to complete carrier depletion in the polycrystal under the base electrode. These results show the high potential of the proposed HBTs for high-speed digital and broadband-amplifier applications.

Characterization and application of calcium ferrites based solid solutions containing active oxygen species for catalysts in propylene total and methane partial oxidation has been studied. The calcium ferrite based solutions containing brownmillerite phases showed a structural transition based on the migration of oxide ions at high temperature. The calcium ferrite solution provided two types of active oxygen species due to the existence of the brownmillerite phase. These oxygen species individually played important roles in the propylene and methane oxidation mechanisms.

BACKGROUND AND OBJECTIVES Granulocyte transfusion therapy (GTX) can be effective for life-threatening infections unresponsive to conventional antimicrobial therapies in severely neutropenic children with cancer. We developed a new granulocyte collection method, named the 'bag method', in which apheresis, hydroxyethyl starch (HES) or dexamethasone are not used. We undertook a pilot study to determine the feasibility and the safety of GTX collected by the bag method for children with cancer and life-threatening infections. MATERIALS AND METHODS A total of 25 GTX were administered to 13 patients (median age 3 years, range: 0.3-17; median weight 10.6 kg, range: 4.5-49.8) with neutropenia-related infections. Thirteen blood-relative donors received granulocyte colony-stimulating factor (G-CSF) (5-10 microg/kg), subcutaneously, 14 h before collection. Major end-points were granulocyte yields, post-transfusion absolute neutrophil counts (ANC) in patients, donor and patient safety, and clinical outcome on day 30. RESULTS The median yield of ANC per 400 ml of processed whole blood was 6.2 x 10(9) (range: 2.5-15.0 x 10(9)). Patients received a mean of 6.4 +/- 0.8 x 10(8) granulocytes per kg of body weight per transfusion. The 1-h and 24-h post-transfusion ANC rose to 607 +/- 124/microl and 704 +/- 300/microl, respectively, from the baseline of 21/microl before the first GTX. Adverse reactions were observed in five of 13 donors (bone pain, headache, vasovagal reaction; all < or = grade 2) and in two of 25 transfusions of 13 patients (transient hypoxia; grade 3). Ten patients had favourable responses, and infection resolved in nine patients. CONCLUSIONS The bag method without apheresis relieves the physical load of donors and enables patients with a low body weight to provide an adequate dose of granulocytes.

We have fabricated InGaP/GaAs double heterojunction bipolar transistors with a sidewall base contact structure. These transistors operate in both emitter-up and emitter-down modes. Symmetric characteristics of the cutoff frequency f/sub T/=68 GHz and the maximum oscillation frequency f/sub max/=31 GHz were obtained at a base-collector bias V/sub BC/ of 0 V. For emitter-down operation, f/sub T/ was found to reach a maximum of 78 GHz when the base-collector junction was forward biased at 0.9 V. The product of f/sub T/ for emitter-down operation and f/sub T/ for emitter-up operation was 5.3/spl times/10/sup 3/ GHz/sup 2/, which is about six times that of previously reported SiGe heterojunction bipolar transistors.

High-speed InGaP/GaAs heterojunction bipolar transistors (HBT's) with a small emitter area are described. WSi is used as the base electrode to fabricate HBT's with a narrow base contact width and a buried SiO/sub 2/ structure. An HBT with an emitter area of 0.8/spl times/5 /spl mu/m exhibited an f/sub T/ of 105 GHz and an f/sub max/ of 120 GHz. These high values are obtained due to the reduction of C/sub BC/ by using buried SiO/sub 2/ with a narrow base contact width, indicating the great potential of GaAs HBT's for high-speed and low-power circuit applications.

Viruses have been suspected to be one of the causes of IgA nephropathy (IgAN). Recent studies have detected viruses in renal tissues of patients with IgAN. Enteroviruses have been reported as pathogenic agents in some renal diseases. We previously reported that group B coxsackieviruses cause pathological changes in experimentally infected mouse kidney. The aim of the present study was to examine the participation of enteroviruses in the pathogenesis of renal diseases including IgAN. Renal biopsies of ten patients with IgAN (group 1) and of 19 patients with non-IgAN renal disease(group 2) were analyzed by polymerase chain reaction (PCR) for the presence of enteroviral RNA. Positive PCR results were obtained for three patients (30%) of group 1. We confirmed by sequencing that the positive PCR products were derived from strains of enteroviruses. One of these three patients also had a positive result for lymphocytes from peripheral blood. In contrast, enteroviral RNA was detected in none of the 19 patients of group 2. The incidence of enteroviral RNA detection in patients of group 1 was higher than that in group 2 (P

The effect of nitrogen concentration on the properties of ZnTe‐based contact structures, which consist of p‐ZnTe layers, ZnSe/ZnTe graded superlattices and p‐ZnSe layers is described. The nitrogen concentration of the ZnTe layer was varied by using a modulation doping method. Ohmic I–V characteristics were observed when the nitrogen concentration of the ZnTe layer was as low as 3×1018 cm−3. When the nitrogen concentration rose above 1×1019 cm−3, however, no current was observed in the I–V curves. Nitrogen diffusion from the ZnTe layer to the superlattice and the ZnSe layer was observed by SIMS analysis and PL measurement. The ZnSe layers became highly resistive, probably because deep donors were induced by the nitrogen diffusion.

Poor thermal conduction of a GaAs substrate in GaAs heterojunction bipolar transistor (HBT) power amplifiers (PAs) previously required thermal designs such as ballast resistors and a large finger pitch (/spl sim/ 30 /spl mu/m). This paper describes the successful fabrication of ballast-free PAs with a small finger pitch (15 /spl mu/m) using a collector-up (C-up) configuration with a backside emitter structure. Having via-holes directly under C-up HBTs is convenient in terms of thermal conduction; PAs composed of multi-finger HBTs in this configuration occupy one-third less area than those with HBTs in the conventional configuration. A small 32-finger C-up HBT we fabricated with a total area of 0.25 /spl times/ 0.31 /spl mu/m/sup 2/ delivered a power-added efficiency of 52% at 24.4 dBm in wide-band CDMA operation. The results show that C-up HBTs with a backside emitter structure have strong potential for microwave high-power application.

In this paper, we have successfully fabricated ballast-free HBTs with L of 15 /spl mu/m and V/sub ce,.sat/ of 0.01 V by employing a backside-emitter-structure collector-up (C-up) configuration with ohmic collector contacts. Preliminary results on performance of these HBTs show their strong potential for application in small and highly efficient PA MMICs.

Electrical properties and microstructures of Au/Pt/Ti/Ni ohmic contacts to p‐type ZnTe were investigated using the transmission line model method and cross‐sectional transmission electron microscopy. The specific contact resistance decreases when the annealing temperature is increased and reaches a minimum at 300 °C. The formation of NiTe2 from the reaction between Ni and ZnTe plays an important role in lowering the contact resistance. A contact stability test performed at 102 °C suggests that these ohmic contacts are stable even under high‐current injection.

A novel structure of InGaP/GaAs collector-up tunneling-collector heterojunction bipolar transistors (C-up TC-HBTs) with sub-transistor via-holes, for use in small power amplifiers, is presented. Having the via-holes directly under the C-up UBTs is convenient in terms of thermal conduction; power amplifiers composed of multi-finger HBTs in this configuration take up dramatically less area than those with devices in the conventional configuration. The result was the demonstration of thermally stable operation for a 4-finger C-up TC-HBT at up to 0.9 mW//spl mu/m/sup 2/, in spite of the low finger pitch of only 15 /spl mu/m. Moreover, a small 32-finger C-up TC-HBT, with a total area of 0.25 /spl times/ 0.31 mm, was capable of delivering a power-added efficiency of 52% at 24.4 dBm in wide-band CDMA operation. These results show the strong potential for microwave application of high-efficiency power amplifiers composed of C-up TC-HBTs.

The diffusion of Be and C in heavily doped polycrystalline GaAs grown by molecular beam epitaxy and metalorganic chemical vapor deposition has been studied by secondary‐ion mass spectrometry and Hall measurement. It is found that Be rapidly diffuses into the undoped buffer layer at a growth temperature of 450 °C. Concentration‐depth profiles of Be in AlGaAs/GaAs heterojunction bipolar transistor layers indicate that Be diffuses mainly along polycrystal grain boundaries. On the other hand, C diffusion is negligible even for post‐growth annealing at 800 °C. However, annealing increases the resistivity of C‐doped GaAs, which is probably due to a change in the occupation site preference of C atoms from As sites.

The interdiffusion of magnesium and iron in gallium nitride (GaN), i.e., magnesium–iron interdiffusion, was investigated using magnesium-doped GaN layers on iron-doped GaN substrates. The investigation confirms that the magnesium–iron interdiffusion strongly depends on the concentrations of magnesium and iron, that is, it occurs when the iron and magnesium concentrations are high (magnesium: 2 × 1020 cm−3; iron: 2 × 1019 cm−3). It also confirms that diffused iron in the magnesium-doped GaN layer acts as a nonradiative recombination center in GaN.

A fabrication technology for AlGaAs/GaAs HBTs (heterojunction bipolar transistors) with low base resistance and low collector capacitance is developed. Self-aligned AlGaAs/GaAs HBTs show a high cutoff frequency of 45 GHz and maximum oscillation frequency of 70 GHz at collector current of 3.5 mA, and were successfully applied to IC chip sets for 10 Gb/s optical transmission. Among the fabricated 10 Gb/s IC chip sets, an AGC amplifier with 20 dB gain and 13.7 GHz bandwidth and a decision circuit with 66 mVp-p of ambiguity at 10 Gb/s are obtained, which are fully applicable to 10 Gb/s systems. >

We have achieved advanced high-frequency performance in small-scaled InGaP/GaAs HBT's due to the further reduction of the parasitic capacitance by refining the device design and the process technology. An f/sub T/ of 156 GHz and an f/sub max/ of 255 GHz were achieved for an HBT with an emitter size S/sub E/ of 0.5/spl times/4.5 1/spl mu/m/sup 2/ at a collector current I/sub C/ of 3.5 mA. A 1/8 static frequency divider using these HBT's operated at a maximum toggle frequency of 39.5 GHz.

The influence of substrate orientation on Be transport during GaAs molecular beam epitaxy is studied by secondary‐ion mass spectrometry. Substrates are misoriented from (100) toward (111)A, and the epitaxial growth is performed at 630 °C for Be doping at (5–7)×1019 cm−3. Surface segregation and anomalous diffusion similarly depend on substrate orientation. With (311)A orientation, the Be transport is dramatically reduced from its value with conventional (100) orientation. These results are qualitatively explained by considering the effect of atomic steps on the growing surface.

To validate the condition for applying thermionic emission (TE) theory when depletion-layer width is larger than carrier mean free path, Schottky barrier height qΦB of reported nickel/n-type gallium-nitride diodes was numerically determined. The forward-current/voltage characteristics of diodes on free-standing substrates were precisely reproduced by qΦB of 0.98 eV. Although this qΦB is consistent with the reported value (0.99 eV) determined from capacitance-voltage measurement, it is 0.05 eV higher than the reported value (0.93 eV) determined from TE theory. This discrepancy indicates that qΦB of GaN Schottky barrier diodes needs to be determined not by analytically but by numerically fitting the experimental data.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective therapy for many hematological malignancies, however, it remains to be limited by morbidity and mortality related to graft-versus-host disease (GVHD). During GVHD, donor T cells are activated by host antigen-presenting cells (APCs) and differentiate into effector cells that mediate host tissue damage. Development of alloreactive effector T cells requires orchestrated expression of myriad genes initiated by host APCs. However, little is known about the key epigenetic factor that controls this process. Histone methylation, which is catalyzed by histone methyltransferanses (HMT), has been correlated with genes encoding effector cytokines and transcription factors critical for effector differentiation. We recently demonstrated that inhibition of histone methylation using 3-Deazaneplanocin A (DZNep) arrested ongoing GVHD through induction of apoptosis in alloreactive T cells. However, since DZNep reduced multiple histone methylation marks, including trimethylation of histone H3 at lysine 4 (H3K4me3), H3K27me3, H3K36me3 and H4K20me3, the key HMT that regulates the transcription program important for allogeneic T cell responses remains unclear. Using genetic approaches and mouse GVHD models, we identify that the HMT Ezh2, which specifically catalyzes H3K27me3 and acts primarily as a gene silencer, plays a central role in regulating allogeneic T cell proliferation, differentiation, and function during the GVHD process. Transfer of donor T cells derived from Ezh2 conditional knockout C57BL/6 (B6) mice did not induce GVHD in lethally irradiated allogeneic BALB/C mice, with all recipients surviving free of disease. In contrast, wild-type (WT) donor B6 T cells caused uniformly lethal GVHD in these recipients. We found that loss of Ezh2 selectively impaired alloantigen-specific T cell responses. Three days after allo-HSCT, both Ezh2-deficient and WT T cells were similarly activated to proliferate in vivo. However, 7 days after transplantation, there was a significant reduction in the number of highly proliferative Ezh2-deficient T cells compared to WT T cells, leading to a dramatic reduction of infiltrating Ezh2-deficient T cells in GVHD target organs. Interestingly, conditionally deleting Ezh2 did not affect proliferation and survival of B6 T cells that were transferred into lethally irradiated syngeneic B6/SJL mice by 7 days after transplantation. Thus, Ezh2 is critical for the continual proliferation of alloantigen-responding T cells during later stages of GVHD induction. In contrast, Ezh2 is dispensable for both the initial activation and proliferation of T cells upon alloantigen-priming and homeostatic expansion of T cells in response to lymphopenia. Previous studies suggest that IFN-g-producing alloreactive effector cells cause damage to the liver and gastrointestinal tract. We found that loss of Ezh2 led to selective reduction in frequency of IFN-γ-producing effector cells 7 days after allo-HSCT. This effect was accompanied with decreased expression of transcription factors TBX21 and STAT4, both of which are crucial for effector differentiation. These data suggest that in addition to regulating the transcription program critical for producing sufficient numbers of alloreactive effector T cells needed to mediate GVHD, Ezh2 is also important for orchestrating genes required to promote IFN-γ production in effector cells. Importantly, we found that Ezh2 ablation retained anti-leukemia activity in alloreactive T cells, leading to improved overall survival of transplant recipients. Collectively, these findings identify Ezh2 as a key epigenetic regulator that controls allogeneic T cell responses and GVHD. We propose that pharmacological modulation of Ezh2 using specific inhibitors should be investigated as a novel therapeutic strategy after allo-HSCT. Disclosures: No relevant conflicts of interest to declare.