45 research outputs found
Unique opportunity to harness polarization in GaN to override the conventional power electronics figure-of-merits
Owing to the large breakdown electric field, wide bandgap semiconductors such
as SiC, GaN, Ga2O3 and diamond based power devices are the focus for next
generation power switching applications. The unipolar trade-off relationship
between the area specific-on resistance and breakdown voltage is often employed
to compare the performance limitation among various materials. The GaN material
system has a unique advantage due to its prominent spontaneous and
piezoelectric polarization effects in GaN, AlN, InN, AlxInyGaN alloys and
flexibility in inserting appropriate heterojunctions thus dramatically broaden
the device design space.Comment: Invited paper, to appear in IEEE Device Research Conference (DRC),
June 201
Stroboscopic Time-of-Flight Neutron Diffraction in Long Pulsed Magnetic Fields
We present proof-of-principle experiments of stroboscopic time-of-flight
(TOF) neutron diffraction in long pulsed magnetic fields. By utilizing electric
double-layer capacitors, we developed a long pulsed magnet for neutron
diffraction measurements, which generates pulsed magnetic fields with the full
widths at the half maximum of more than ms. The field variation is slow
enough to be approximated as a steady field within the time scale of a
polychromatic neutron pulse passing through a sample placed in a distance of
the order of m from the neutron source. This enables us to efficiently
explore the reciprocal space using a wide range of neutron wavelength in high
magnetic fields. We applied this technique to investigate field-induced
magnetic phases in the triangular lattice antiferromagnets
CuFeGaO ().Comment: 9 pages, 7 figure
Successful Treatment in a Case of Massive Hepatocellular Carcinoma with Paraneoplastic Syndrome
Paraneoplastic syndromes of hepatocellular carcinoma (HCC) are not uncommon. However, the prognosis is poor and follow-up and improvement of paraneoplastic syndromes with treatment have been reported rarely. We report a successful case in an aged man of a massive HCC with paraneoplastic syndrome, treated by combined intraarterial chemotherapy and hepatic resection. Paraneoplastic syndrome (erythrocytosis and hyperlipidemia) was monitored throughout the treatment and erythropoietin (EPO) mRNA also was analyzed in the resected liver. The hemoglobin level and serum levels of EPO and total cholesterol (T-cho) decreased dramatically with treatment, along with a decrease in serum levels of α-fetoprotein and protein induced by vitamin vitamin K absence II (PIVKA-II). Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) revealed that the residual cancer expressed EPO RNA but the nontumor tissue did not. This was a rare case of paraneoplastic syndrome of HCC that was treated successfully. This case indicates that paraneoplastic syndrome reflected tumor progression and that serum levels of both EPO and T-cho might be used as tumor markers
Breakdown Walkout in Polarization-Doped Vertical GaN Diodes
We demonstrate the avalanche capability and the existence of breakdown walkout in GaN-on-GaN vertical devices with polarization doping. By means of combined electrical and optical characterization, we demonstrate the following original results: 1) vertical p-n junctions with polarization doping have avalanche capability; 2) stress in avalanche regime induces an increase in breakdown voltage, referred to as breakdown walkout; 3) this process is fully-recoverable, thus being related to a trapping mechanism; 4) temperature-dependent measurements of the breakdown walkout identify defects responsible for this process; and 5) capacitance deep level transient spectroscopy (C-DLTS) and deep level optical spectroscopy (DLOS) confirm the presence of residual carbon in the devices under test. A possible model to explain the avalanche walkout is then proposed